There will be more,

There will be more, many projects were put on hold due to some other construction matters.

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So what color was the dress?

So what color was that dress?

In the grand scheme of things- not newsworthy, yet it made international news. As for why it looked different? Several factors come together- and it has nothing to do with the psychobable that the US underwater basket weavers want you to believe.

There are a few factors influencing how something looks on an LCD screen. Color saturation, Hue, contrast, tint and more importantly the viewing angle. The lighting conditions of where that first image was taken is also a factor. If you do not think viewing angle is important- turn on your TV set or place your computer monitor in a spot on the desk where you can view it while laying on the floor.

Then ask yourself this- did you ever adjust any of those settings on your computer, your TV set or your smart phone? Chances are the answer is no. But even if you had, the way you have yours set it may not render everything accurately. So an image taken under mixed lighting, and while digital cameras usually auto adjust the white and black balance to the exisitng conditions, if you have the camera positioned in a way that it renders color hues as if it is under flourescent or incandescant lighting but you get an influx of daylight into the area being imaged, the sunlight may render the subject a little towards the blue end of the spectrum- and while black is not always going to show other hues of light falling upon it, plus your eyes compensate quite well (which allows digital abberations to occur without notice), keep in mind it is being translated to binary coding. So how it is viewed on the second LCD screen (the first recipient of that image), depending how it is set up, and if someone else was looking over that person’s phone from an odd angle, it is very likely what started that whole chain of events.

So the psychologists and psychiatrists got it wrong. But then the underwater basket weavers do not know enough about technology to understand this post even, it logically explains why they would rely on the psychobable answers.

Now- Why do you lay down on the floor and look at your TV set, or computer monitor? Or your tablet, laptop or smartphone upside down? Simple- it reveals how light is bent by the difracting material that is part of the backlighting of the LCD screen. If you take apart a typical LCD display, you have the LCD panel and beneath that a sheet of translucent clear material, with prismatic sheets beneath that with ultimately an acrylic sheet beneath that. The prismatic sheets are not exactly polarizing the light, but it is bending the backlighting and helping to difuse it otherwise you would see the areas in front of the CFL tubes or the LED strip as brighter than the rest of the screen.

So what happens is the LCD screen is seeing behind it and transmitting that light that is almost polarized, (and some LCD panels have a layer of polarization material to help elminate those “hot spots” as well), so the light becomes fully polarized and as a result, the acceptable viewing angle of the LCD Panel itself narrows. As a result, when you view it outside of the normal viewing angle, black can become white or some shade of blue, etc- the image “almost” becomes a negative of the actual image.

So whatever color you see of that dress- it is not in your head- it is in the display device. Add to that the usual bias towards a white with a very slight bluish tint is often considered “more white” than “true white”.

But don’t expect any reporter/underwater basketweaver to get it right- it is too far over their head.

I will be doing some crossposting from some of my other blogs to here, so stay tuned. Atroubleshooting series will be up soon

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

an old house renovation blog

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

Posted in Assorted odds and ends, Uncategorized | Tagged , ,

Making Your Batteries Last.

I may have mentioned this previously as part of another post, but I am going to cover just the rechargable batteries in this post. Namely how to make them last as long as they were designed for. Why is this important? When I handle items being recycled at an organized collection, there are often numerous battery powered devices that are not that old. Why? For many, it is because the batteries have cooked out. This is the result of leaving an item on the charger contiuously until needed. From cordless phones, cell phones, power tools, and others.

I will just mention that if you have a number of “primary cells”/ batteries, and they are not going to get used for long time- put them in your freezer inside of a sealed plastic bag to reduce the potential for them tor dry out- this will make them last a very long time until they are needed. When needed, just let them thaw out before putting them into service.

To make the batteries last their longest, charge them fully with their charger they came with before first use. If the item is not going to be used for a while, just pull the battery out once it is fully charged. The reason why to do this is memory circuits can draw a great deal of current such as the IRobot “Roomba”. It maps while it does it’s thing and that map is retained in memory. Unplugging the battery does clear the memory, the tradeoff is the battery will discharge significantly in just a few days if left plugged into the machine.

Cameras are another item. The “Everio” cameras will discharge the battery in a few weeks or less even though the memory is not needing to draw current from that main battery, it is just the parasitic load of the power standby circuit. Charging the battery and then removing it from the camera will make it last longer. The memory sticks you plug into the camera do not require power to maintain the images. This is true of many cameras.

Now there are different technologies employed in these types of batteries. Different materials and constructions: however they share the same component in their electrolyte- water. I have dismantled many battery packs and it is not uncommon to find NiCads and NiMh types to have been boiled out- indicated by the mineral salts left behind near the venting holes in the cell. Most have a design life measured in “charge cycles”- if you circumvent the original design by placing the item back on the charger immediately after use believing that the battery must be kept up like that you will be replacing battery packs quite often and needlessly. Cordless phones and cell phones are a perfect example. NiCads also exhibit a “memory” when this “short cycling” is done which reduces the amount of use you can get from it later. The memory can sometimes be undone by discharging fully and recharging fully to “recondition it a few times, but once a cell has lost a certain amount of water- it’s capacity is greatly reduced and cannot be recovered by “reconditioning” it.

The short answer to extending battery life is to charge it fully initially, then leaving the device off of the charger until the power indicator indicates a recharge is needed, or if the device shows a very degraded operation- such as a cordless drill that barely rotates. Just because a cordless drill slows slightly does not mean to throw it on a charger- use it until you need to actually rotate the screw with the screw gun itself and only then put it on charge. While it may not seem fully practical on a construction site, you need to find that balance point because I am using battery packs that are about 10 years old in some cases.

Emergency flourescent lighting systems produced by a number of companies put a continuous float charge on the Nicads used by most of them, which cooks out most of them after a year, and since most are not made in a manner that lends itself to battery cell replacements, they are effectively “disposable”. I have salvaged a number of units and modified them for use elsewhere, but they are effectively similar in principle to the cold Cathode Flourescent lighting systems used in backlit LCD panels- be they laptop computers, monitors or TV sets.

Many public schools have tried to push kids into using tablet computers or laptops- these at best are going to be a yearly expense, and a needless one for numeorus reasons, but most school boards are not known to be intelligent nor able to make intelligent decisions, or the correct decisions. A black board or a white board do not need batteries to be used effectively. One has to question if the push to technology so early is due to a lack of teaching ability or a desire to keep kids quiet? Are they truly learning anything more than they would learn by way blackboards and whiteboards and an effective teacher? Based on what I see these days the answer is clearly “No”, just look at how many misspelled words there are in many newspapers these days, or sites with free ads. In My opinion, computers should not be introduced into classrooms until 7th grade at the earliest, and even then- only for students to learn some programming or code writing. Otherwise technology should not be a requirement until Freshman year of high school- even then limited in it’s use because the technology becomes a crutch.

But the problem with technology when it is in use is that of the batteries- most of the time people do not use their laptops or pad computers untethered from their charger. This means the batteries are getting constant current to refresh them but that is also forcing water vapor or Oxygen or Hydrogen even- out of the battery cells thus “cooking them” so they will never see the full life cycle capability of the battery.

Chargers have come a long way since the initial adoption of cordless drills in industry. But the chargers are not sophisticated enough to fully shut off when charging a partially charged battery, nor are they sophisticated enough to recognize a partially charged battery and either not charge or it will charge the battery as if it were fully depleted.

Now in home power systems, the batteries are mmot likely to be Lead Acid of some variant. The byproduct of charging any of them is hydrogen as a gas. The flooded wet cell types can be desulphated or “equalized” by an application of current at a potential above the “gassing point”. Usually above 16 volts for a 12 volt battery. Sometimes this requires pulsing initially to get the process started, but once begun, it can be very effective at salvaging some flooded cell types.

The lead acid variants should never be charged at an “Equalization” point as they are designed with a finite quantity of water assuming a finite charge cycle with specific charge potential requirements with essentially a finite life expectancy. Many back up power systems use AGM types of lead acid battery which are this sort of battery. Most of the time they are on a “float charge” when not in use- this gives them a very finite life span as it still reduces water in the electrolyte to hydrogen and Oxygen. These are NOT good sources for batteries for a home power system unless one is scrapping them in order to buy new batteries. Phone systems however change out their backup batteries (usually AGM’s) on an annual basis, and those usually have some potential for use in a home power system.

With Boeing using Lithium Ion batteries now in some of it’s new airliners, it is not long before we see some made for automotive or residential uses other than in the Hybrid vehicle’s battery systems. These have rather strict charging requirements and will cause fires when incorrectly charged- or they explode. Which is why I always discussed “NOT” using any of the chargers I presented or other battery charger projects to charge Lithium types other than the chargers that were designed for them. Plus Lithium is also a very toxic metal, and while it has some use in medicine, it is in trace or small amounts only. While Lithium types have potetial for home power systems, at this time they are not going to be discussed in a home power system application due to their highly toxic nature and charging issues.

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http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

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The passive solar blog- outgrowth from some projects of mine.

Posted in Batteries, Battery charger, Capacitive charger, Capacitor charger, charger, Primary Cells, Recycling, Uncategorized | Tagged , ,

A Quick Overview of Tube Testing…

A few notes here, mainly on tube testing and just some commentary on why tube sound is popular.

Visually, you cannot tell merit of a tube, but you can at least determine if it has damage to the seal or the envelope by the way the “getter flash” appears. If it is shiny, the seal is at least adequate. If it is white- the seal is gone or the tube is damaged. The “flash” is the final production step where a high voltage is applied to the pin the getter is attached to and an external “anode” is wrapped around the tube. The Barium compound becomes transferred to the glass by the electron flow and chemical reaction in the process, remaining gasses (primarily those that are reactive to metals) are bound chemically with the barium compounds through the chemical reactions.

First, there is no perfect test or tester. Some cost more than others because of how they go about establishing a reading and this reflects the sophistication of the tester. The basic testers are “Emissions” testers. These work but are not great when it comes to matching tubes but if nothing else is available, they will allow some degree of matching accuracy. Also if an emission type is all you have available, and you are trying to match tubes, you need to strive for the same reading on the meter for both tubes or tube sections.

What does “Tube balancing mean? and is it impotant?”.
Tube Balance: simply means that either 2 tubes in the same location in the circuit of a stereo have the same measurement of performance, or when they are in a “push- pull” circuit (usually an audio output), the tubes should have the same value so the output waveform is correct and balanced above and below the “Zero Crossing Point” because one tube is amplifying the upper half of the wave and the lower half of the wave is handled by the other tube. Depending how an amplifier is wired determines how critical the tube balance is for decent performance, but it is always better to have tubes with the same performance working together.

Zero Calibration

Zero Calibration screw- only sets where the needle comes to rest for “Zero”

I am mainly addressing this to “Guitar Amps” and “Monoblock” amps, but stereo amps are similar in some respects as you can see in the image below at the bottom of the image. When you are dealing with guitar amps with some effects in them, the tube balance is critical to be close when compairing the 2 sections of a 12AT7 when used as a driver for a reverb tank. Other tubes can be used here depending who designed the amp, but in many amps, this tube is a 12AT7 wired so both sections of the tube are operating in parallel. These sections need to be close, and over time they will even out as the tube begins to age in the circuit if the tube is new or nearly new with only a slight difference in values between the sections, but over the course of a few thousand hours, and sometimes even a few hundred hours, the merit of the two tube sections begin to diverge again. In time, when it gets bad enough, you lose the reverb effect because the tube sections reach a point where they are inadequate to drive the reverb tank.

Phase inverter

Schematic chunk for reference

In the image you can see part of the schematic, mainly that part where tube balance is best exemplified. V7 and V8 in the image are the 6L6 finals (Output tubes), and half of V6 is the phase inverter. Even though V6 does not introduce much gain into the circuit, it is one of the tubes where a close balance is desired. While I know the amp I built in an earlier post used random box pulls that were not tested, but still sounded decent that was by chance only. I fully expected a muddy sound because I at least knew the 6L6 series tubes I pulled were tubes that tested low when tested previously and did differ in merit, but I do hold onto these old weak tubes simply for initial testing in circuits just in case there is an issue- why risk a good tube in an untested circuit? But it was a demonstration that it is the circuit that ultimately determines the real merit of the tubes.

When a tube has been checked for balance by various vendors you usually see “Gm” or the m can be subscript followed by a number. That number is units of “µMhos”. The relative conductivity of the tube or section of tube from which you can judge to some degree the merit of “Age” for the intent of balance. In other words, given a box of random tubes of a certain type, if you need to “match” them for the circuit they are to be in, you want them to be very close- Some may insist they be exactly the same value, but the reality is that if you are within 5%, (the Gm numbers differ only by 5% or less difference) you have a decent match, but the closer you can get to identical measurments, the better the match.

Now, there are several Push-Pull topologies, I am not going into those descriptions here, I am simply discussing testing tubes and what someone should be looking at when testing tubes. When the output of an amplifier has just one ouput tube- it is considered “Single Ended” and in a stereo you would just want the 2 output tubes (1 in each channel) to be very close if not identical in performance (if a slight imbalance in audio can be heard, it can be corrected with the audio balance control when a difference is noted.).

Now, when you get to tube stereo’s or 2 mono block amplifiers used for all intents and purposes as a stereo: when you are selecting matched tubes, the reason here is that when you have a 2 section tube such as a 12AX7, 6SN7, 6N7 and others- when they are used in the “preamplifier stages”, “Voltage Gain” stages/driving stages etc- One section of a 12AX7 or one half of the tube is handling one channel (right or left) and the other half of the tube is handling the same function for that other channel. In a dual monoblock setup you are looking to match the tubes so that the tube in one location of the circuit in amplifier “1” has the same values as the tube in the same location of amp “2”. This is true until you reach the phase inverter of a “Push-Pull” amplifier, and the finals or output tubes where for each amp you want balance in that amp’s finals or phase inverter when it is a multi section tube.

pic of monoblock

Generalized tube locations and functions.

In other words: referencing the image- V1 of Amp 1 should match V1 of Amp 2. V3 being the phase inverter should have both sections of the tube match*. V4 and V5 of each amp should match each other. if a “quad match” is sought, V4 and V5 of amp 1 and V4 and V5 of amp 2 need to match.

The image of the “Hypothetical Amplifier” shows a generalized signal path through the tubes, and should give an idea why stereos should have balanced tubes in their stages in a manner different from the monoblocks. Even though it seems there to be a difference between the 2 amplifier types, in approach to the process of tube balancing, it is actually the same process- to ensure the chatacteristics at each stage of the amplifier is the same for the 2 stages be they on one chassis or two.

*note-If the phase inverter is performed with a single section tube like a 6C4 or 6C5/6J5, then you just want to match them between the amps as you did V1 and V2. or if the single phase inverter is the same as the tube driving the grid of one of the finals. In other words- if in the chunk of Feneder schematic that V6A and V6B were actually discrete tubes- those 2 tubes you want to be close matches to each other (most important) and secondarily to their counterparts in the other monoblock. (I am glossing over some of the details of those amps with single section tubes in the phase inverter location to keep the discussion simple.) However: if V1, V2 and V3 are the same type- is is not critical that they match each on the single amp, just critical to match V1 (amp1) and V1 (amp2). (I am not going to delve into design theory because that would complicate this discussion needlessly, which is why I try not to dwell on minutae or too much jargon. Some people just live for jargon and it’s absolute correct usage- those people like to get lost in it. I am not one of those people because it really does not serve a critical purpose in the grand scheme of life.)

The ultimate test of merit of a tube is how the tube performs in the circuit. While a tester can tell you something about the merit of a tube within the circuit characteristics of that tester, the tube is normally not seeing the same circuit conditions with a tester that it sees in use. The ultimate final test is how well a tube sounds in a circuit. Some radios are not critical to what merit tubes they get, especially in series string heaters/filaments. So don’t automatically throw your tubes that measure “bad” or “?” in merit unless you are a dealer of tubes. Those weaker tubes however, you can wholesale at a Hamfest. Someone like me- I sometimes gamble on those tubes. Why? Because I have some secrets, and for some tubes- I have radios and other items that will work well enough with borderline and weak tubes that it does not matter too much.

The only thing not discussed yet in this topic is the rectifier. If solid state rectification is used- no problem. If a rectifier tube is used, ideally you want the 2 sections to be close to identical if it is a “Full Wave Rectifier” like 5U4, 5Y3, 5V4, 80, 5AR4, etc. But there are times that may not be possible. In most cases, you can have a difference between the 2 sections of a full wave rectifier tube with a difference of up to 20% before a degradation of audio performance is easily noted, and where in the life cycle of the tube that difference develops in will also factor in. And while not usually given a great deal of discussion goes into these, it is largely due to the forgiving nature of tubes, it is something worth mention here though. Other Rectifiers, like the 35Z3, 35Z4, are “Half Wave” rectifiers and only have one plate and one cathode. As long as the device performs acceptably, you can run with these as long as you want to, but after a certain point sound quality degrades as does sensitivity.

Bottom line is this- even if a tube tests low- Sometimes it “can” be just the tester, and sometimes not- but a tester should not be the final arbitter of functionality.

Now that value you have from a tester is going to be arbitrary, but it still has a meaning. The measurement relates to how well the tube conducts between the cathode and the plate for that type. Testers vary, even when testing a tube on 2 different testers- usually 2 different values are measured. So having more than one tester is not a crime and is actually a good idea. The one tester I have the post on a few months back- it is actually more reliable for testing older tubes such as those mentioned above, but it also tends to test many of the 6S_7 series tubes lower than they test on a Jackson 648 or Sencore. Even numbers derived from an Eico 650, or TV7 series tester will vary, and they will sometimes vary significantly from an “Emission” type tester for the same exact tube. The latter 2 measure transcondcutance quite accurately when calibrated, and that type of tester tends to be used by the tube vendors. Now, tubes that were tested strong at the tester plate voltage of 150 to 170 volts, and their measurements are close, when they are in circuit and seeing 450 volts on the plates, they will in a vast majority of instances, perform as they are supposed to with minimal noise and minimal distortion (unless your goal is for massive distortion.). In other words, if the tubes are good on the tester, they will be proportionally about the same difference they were in the tester when in use. But “Hot spots” on the heater or filament that make a tube seem adequate in an emission type tester, may fade when in the operating circuit and in turn lead to degraded performance; a “Mutual Conductance” type of tester will usually be immune to false readings from hot spots.

Now, when you have matching pairs, referring back to the 2 hypothetical monoblocks, assuming you have tested the tubes and paired them, and that V1-V4 are the same type, but you have a pair that measures at “120” on the tester, the next pair tests at “110”, the next pair tests at “100” and the next pair tests at “90”; usually you will have the best results with the highest ratings at the first tube (usually highest gain) of the amplifier section. followed by the next tube location getting the next highest, etc. Older tubes tend to develop some noise, and the less amplification of that noise is better achieved by having the best tubes in the early higher gain stages.

As a real life example or compairison, the above paragraph is what I used to do with Tube type TV sets, especially with color TV sets (and while I did the same thing with black and white sets, there were fewer tubes of the same type number, but the principle worked there as well.), was in situations where you have for example- 3 “6GH8” types as the three amplifier stages for video IF, I would put the highest measured value in that first IF section as it is the most critical. Purists would insist on realignment if this were done and especially if that tube came from a different spot- the reality is you do not need to be so picky about the alignment because the set when new was aligned to new tubes- not aged tubes, so unless you fully retube the set with new tubes, you are just making a lot of work for yourself when you really do not need to, and while there is some merit to the notion that the tube is going to age to the circuit it is in, there is only “some” merit to that way of thinking because the tube is itself going to age from use, it will change more in characteristics after 1000 or 2000 hours of use than the other components of the circuit short of a component failure. In this day and age where such sets are a novelty, kept as “retro” decor, or for sentimental reasons, the alignment is not so critical when the source is a digital converter box or VCR because there is only the one channel being used unless you are next door to a low power TV transmitter still broadcasting NTSC signals. (If your digital set is picking up extra blank stations, it is simply detecting the carrier signal only of either a low power station, or is processing some of the carrier of the stations you are recieving when they do not fall in the spectrum location the ASTC set’s program algorythm.). If major repairs are made with the video or audio circuits, such as replacing “IF” transformers, then alignment is likely needed for at least that one “IF”, but to set up the equipment and adjust that one, you may as well do the rest. Essentially the alignment peaks the set for reception sensitivity, color detection, “Quadrature” (for the NTSC color standard), audio and to reduce adjacent channel noise.

The basis I used for this practice with used tubes developed from discussing with my dad when he was stationed in Labrador for the US Coast Guard. Most of their supplies came in via air drop from the PBY “Catalina” aircraft with only a few actual periodic boat landings. Even ruggedized tubes don’t do well, and sometimes shipments were lost due the wind pulling the parachute across the tundra. As a result, and due to their critical operation of the LORAN station there, when they would come up short in the routine tube replacements he would sit down and test the tubes they had used, and put those in the less critical locations of the equipment with no notable degradation of performance (if any). This kept them online and in a few instances, they were using tested used tubes in critical loactions because they did not have new stock for any of several valid reasons.

I kept 2 different color TV’s going with acceptable color, reception and dot alignment for several years just by keeping the critical stages fed with the strongest used tubes (or new ones when needed) and doing it in this way while never bothering with alignment- they worked fine and I got adequate signal without any problems, but I would adjust the convergence for best picture clarity and color rendering once in a while using a simple computer program and an Atari computer hooked up tot he set to project a series of dots in strategic places on the screen. Unless the picture tube was replaced, alignment was not even considered.

Now I mention a number of times now of letting the equipment be the final arbitter of the tube’s merit. This is simply because some circuits are not super critical to the tube’s “measured” value, and there is no question there are some pieces of equipment that are very critical of having even acceptable tubes from the tester not being good enough for the circuit (I have a Dumont scope like the one in the “Raj Mahal” which is that way.). Conversely I have a tube radio chassis that has all 5 of it’s tubes test below the question mark, and yet reception is very strong, sound quality is as good as a typical table radio and everything works as it should. In an audio amp, this leaves a grey area because people will listen for different things, from clarity (weak tubes usually lead to less clarity- Cymbals and “Hi Hats” tend to sound like static rather than as they are supposed to sound live. “Fricatives” become unintelligible in the spoken word when tubes get too weak and they sound like a drawn out hiss. This also leads to less clarity of the music, and which type of music you listen to- this is critical because some types of music have so much distortion in the music master recording that you cannot discern any difference- Classical music in general on the other hand is quite precise and therefore pretty good for audio evaluations. A song like Anjule’s “Boom”- is terrible for testing purposes. I am not being critical of the song itself, just pointing out that for testing audio it is just not a good candidate when you listen for clarity.

People also wonder “what” they should be hearing when listening to tube audio. Me- I listen for clarity. I have a Sherwood S5000II rated for 80 Watts per channel. Right now I have it connected to a pair of KLH “9912” 3way speakers. I am not overly impressed with the KLH speakers on the Sherwood, but it is more a matter of trying to find the speakers that sound best to me paired with that amplifier. This is not to say the KLH are somehow “defective”, they are not defective, but they were made for a solid state amplifier so they tend to be a little bit damped in their response. I am also one of those who can taste the difference between Coke sweetend with HFCS (tastes like battery acid) Coke sweetened with Cane sugar, Pepsi and RC colas. It is just one of those things that simply “is”. No parsing intended. If you cannot taste the differences, no big deal. If you cannot hear any differences- again, no big deal, but understand people can hear differences.

If you cannot hear a difference between a portable stereo and one of my audio systems, it is not a crime, it just means you likely do not have an apreciation for music or never heard live music, or just have not had some subtle differences explained to you in what you are hearing. Most people will automatically hear a difference even though they may not be able to explain why when they hear the same piece of music played over a decent tube amp and a decent solid state amp. In a similar and unrelated vein- people will usually see the color white as being a more truer white if there is just the slightest tinge of blue to it- blame it on genes, evolution, whatever you like. The fact is that any color viewed under daylight conditions will render different under flourescent and different under incandescant lighting. Or wines- to many, they all taste either astringent or like grape juice, but once a person learns “what” to smell for or “what” to taste for, they can appreciate the differences between Pignot Noir, Chardonay, Pinot Grigot, etc. But if you just buy the cheap wines, sometimes they will taste the same- sometimes blah, sometimes tollerable. It happens. If you happen to run at the sight of a “box” wine- you already know what I am saying.

And when it comes to hearing- people are going to hear in the same piece of music different things in a different way. Most people do not hear the crickets in a city unless one is in their room or close by within the building. In that example it is more likely they just never purposely listened for them because they will hear them all over once they are pointed out or they make an effort to hear listen for them. In that same way different speakers will sound different when played through the same amplifier- there are some quantifiable and measurable differences with speakers and it is a matter of those differences within the speaker enclosure, the overlapping of the frequency rolloff of crossover networks within the speakers, the room shape, wall and floor treatments, box reinforcements etc. Many things can be quantified- but regardless; what I hear and listen for may or may not be what the Bose engineers listen for when not analyzing graphs of sound pressure levels and response curves, or anyone else. This is the realm where amplifier construction and design becomes an art form- because in spite of the quantifiable measurements- there is the human factor, the unquantifiable “Subjective” values that come into play, and sometimes- if you are not measuring the right things- you just won’t be able to measure it. I know someone who will at one moment describe how good his speakers sound, and then crank the volume to an uncomfortable level with Grateful Dead playing. Is his “ear” any better than mine? No, and I am inclined to believe my ear is better but the gist of it is simply this; it just means he does not listen for the same criteria I do.

And some things which some take as a “rule of thumb” just are not true. Some people think a 12 inch speaker is going to automatically have a lower frequency response than a 10 inch speaker- which is absolutely not true. While the physics can support that as a general rule and it may be largely a truism much of the time, the voice coil size, the resiliance of the spider, the magnetic flux of the speaker magnet- all of those plus the cone material and the dust cover (that little bit of felt, fabric or foil over the center of the speaker) wire size, air gap, all of these factor in. But there are some 10 speakers and even some 8 inch speakers that have a lower frequency response than some 12 or 15 inch speakers can have (but not always and not automatically). The problems arise of mass and momentum of the cone with larger speakers because the combinations may not allow for adequate air movement to reproduce the lower frequencies audibly or accurately. This why 20 inch speakers (I had and sold a pair of them once upon a time) are not that common in home stereos- and the pair I had were made for a home stereo (a 1950’s or 60’s era Philco in fact), but they were huge. When I bought them originally at a yard sale, that put an end to further sales that day as I had no room left in the vehicle. But what I listen for is clarity of the sound- “can I hear the metal triangle playing in the background?”, “…does the music sound shrouded or tight and plastic?”, things that are quantifiable in a way, but not always easily explained. I have listend to all sorts of music live in person, and judge some of what I hear based on that experience- “Are the brass bright and clear and in balance with the rest of the music?”.

Some music, such as Pink Floyd’s “Time” or “Dark Side of the Moon” should have a certain sound quality- the bongos should sound as if they are being played in a large auditorium and be “open” and “airy” while having some reverberation, and the bass chords should be able to be felt, yet still a bit airy and clean. This is what I listen for- but others will listen for other things. Some just want volume or sound pressure and if the speakers don’t distort or the amp doesn’t clip, they think it’s “good”, when in reality all they have is a great deal of noise. Noise is more common a problem in apartment buildings because they are not built with audio in mind, so over the years when people tended to listen to their music a little too loud next door to me, I had a wonderful combination of gear that shut down a “Grateful Dead” party moments after it began at 02:00 one morning. and at another time drove an ignorant individual to the point of blowing out their own speakers because they put their speakers on the wall common between our apartments. After the second one blew out his speakers it was only then they then decided it would be prudent if they moved them off that wall, but they tried to make do with scraping vocie coils for a few days and terrible sound that resulted. Good audio is not at all about being a menace with it, but there are times when you just get tired and circumstances warrant full volume practices, and when correctly matched pieces come together, the junk falls by the wayside.

People get enamored with noise specs and THD (Total harmonic Distortion), well, most of those specs are generated at levels people are not going to be listening to on a regular basis, so the published specs are close to worthless. A more accurate measure is how noisy is the amp at full volume with no input signal. That “hiss” you may or may not hear is largely a product of what is in the amplifier, produced as spurious electrons in the audio chain- as your volume level goes up so does the amount of that audio detritus that you are hearing in the “hiss”.

Hiss is NOT THD. Total Harmonic Distortion has to do with the noise that the applied signal generates in that amplifier. A 100Hz pure tone applied to a tube amp will have some 2nd order harmonics (200hz), some 4th order (800Hz) which are all “tonal”- while typically fairly small values in good tube amps, they are still present and part of the reason tube amps have a warm sound and a loyal following. If you go to a piano keyboard, say you press the white key between the 2 black keys at the left. Now go up one actave, this would be a second harmonic of the first, now go up 2 octaves from that key and you have the 4th order harmonic of that first key. If those were all played together, the chord would be okay to your ears. Solid state amps, have primarly third order harmoincs, which would be 300 Hz to that 100 Hz signal mentioned above. It is not quite as harmonious as the even order harmoincs, and even though the ratings for solid state noise are measured at sound levels you cannot tollerate for long, at normal listening levels, they are a little bit higher than the ratings, but because the amount is lower as a percentage overall and not as harmoious, the solid state amps tend to be sterile in sound- which is not automatically bad, but that “warmth” that tube amps have is a bit more difficult to achieve in a solid state amp, and many have tried.

What about power? Usefull to have so the amp can reproduce low frequency signals cleanly at lower volumes, but there is a difference in ratings from old to new. The Class “D” amps which weight barely anything rely on “peak” power ratings. Not RMS. RMS ratings denote a comparable power level to that achieved by the same amount of energy equivalence to DC. Fact is most RMS values for class “D” amplifiers is quite low. 2400 Watts for example from a class “D” amplifier on a 12 volt circuit is 200 Amps- your car starter does not draw that much energy unless very worn or very cold. And that little shoebox amplifier is being fed with a wire that would more accurately be a fuse for 200 Amps- let’s be real here, the instantaneous power is only for a short portion of a second, where as the RMS value is the continuous value averaged over time. Plus the speakers themselves factor in as well. A low power amp, such as a 6Watt Push Pull 6V6 Amplifier with the right speakers attached will do nicely in small rooms. People get buried in numbers and specs as much as people get buried in minutae and in so doing they fail to appreciate what goes beyond numbers- the experience and the quality of the sound.

I have another post in the works regarding how the tubes/valves work and how they are generally classified.

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

The associated blog for above youtube channel

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

http://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.

Posted in Amplifier repairs, Auditorium equipment, Cathode Ray Tube, CRT, Homebrew, Project, recievers and tuners and guitar amps, Repair, Stereo amps, Tube tester repair, Uncategorized, updating tube tester | Tagged , , , , , , , , , ,

Halloween is coming up, build a “Frank’s Box” and see what you find.

…Or not.

Now normally I would only post something that I have built, but I came across this while looking for something else, and it looked intriguing. And since it could mean some entertainment, it might be worth a look for some. Does it work? While I have my doubts, it is none the less intriguing. The item is most commonly known as “Frank’s Box” or “The Ghostbox”, “Telephone to the dead”, and others. Devised by Frank Sumption, who was a ghost hunter the function is in large part predicated on “spirit presences” some people experience have some electro magnetic phenomena associated with them. I am not a ghost hunter, nor do I plan to go on such an expedition, but anyone who has walked around the “Fench Quarter,” of New Orleans will find many stores and tours that are ghost related or paranormal related, not counting the myriad of Voodoo or Santeria related stores, that will attest to the different “feel” of that area compared to the rest of the city. Plus there is such a storied past that if ghosts exist anywhere, the French Quarter is going to have them. However, this does raise some questions as to effectiveness of such a device because apparently some ghosts do not know that they are ghosts so if they are not aware they are ghosts how are they going to know how to communicate? This does potentially raise some compairisons to Ouija boards, which I am not going to delve into unless someone has a “kitable” electronic version devised.

In addition to the presupposition of electromagnetic influence is the assertion that across the radio spectrum in any given area of an industrialized country that there are myriads of different words being broadcast at any given moment, and that you can assemble a conversation or at least half of it by sampling them in sequence from the RF hash that surrounds us via an electrically tuned radio reciever (at it’s simplest description Think in terms of something vaguely like a Theramin only producing voice samples as the output. ). That is the basic principle of the device. Does it work? I cannot tell you it will nor can I tell you it will not. There seems to be a lot written about it trying to explain it, but none are even close to the short description I give.

The underlying premise of “Frank’s Box” being sampled audio: assembling a conversation from random spoken voices speaking simultaneously in a dinner party for example; is not unique, nor should it be considered impossible because as a kid, my friend and I had a cassette player with a spoken word presentation on it. Just on a lark we started to make commentary recording it onto the tape, and we would play it back. Neither one of us had any idea what was even on the tape nor the subject, but we had essentially compiled a 5 minute 2 way conversation on that tape essentially out of randomness until we got bored with it and set it down. What we had done along the way might be called cheating, but it really wasn’t because we would stop at a point, rewind and then play it forward and be surprised that the points where we stopped had relevent replies to our commentary. Where we would stop it and begin to record some other comments was random, we would play for only a couple of seconds to hear the replies and nothing more; stop the tape and then begin recording the next commentary from that stopping point never listening ahead. While you can do this thoughtfully with some spoken word tapes much like an audio editor may piece together or edit interviews: we were not thinking anything into the activity we were just being bratty little kids tormenting a defenseless audio presentation, and really nothing more than that. The randomness from it came the fact were were not trying to line up edit cuts or anything at all like that but the fact that we were able to generate the conversation in such a random manner, and we never knew where we were stopping that tape in the original recorded presentation mind you because we never listened ahead of where we stopped for reply.

And while this is just an annecdote, it is adequate to support the notion that you at least in theory are able to sample from the spoken and sung words in the airwaves at any instant in most any area of at least the US and much of populous Canada, Europe and industrialized Oz, NZ, Asia and South and Central America that you can create coherent speech patterns and sentences from the samplings and thus form complete coherent sentences. It is after all ir is remotely similar in concept to a “Book Cipher”, (which if you can locate a book that Google has not scanned into it’s library, you can create a converstation suitable for letterwriting and replies that Google, the NSA or other agencies would be unable to break unless they too had that specific book- but mix things up if you do so as it was rigid Nazi protocol that led to the cracking of the Enigma encoding device.). But it does require the recipient to have that same title and edition of book to work. While it is a slight stretch for compairison- it is not that much of a stretch because in that compairison, it is a demonstration that you are in essence creating a conversation from fragments of other conversations (written sampling as opposed to audio sampling). While difficult for some to wrap their head around the idea, for others it should be a simply an- “Oh!” or “A-HA!” moment, where seemingly disparate concepts congeal into an understanding of what the concept is. The device on a conceptual level is rather simple.

On the assembly level as Frank designed things, electrically it is probably more difficult than it needs to be.

http://ghosthuntersofamerica.com/franksbox/Franks_box_6-19.pdf
http://www.keyportparanormal.com/images/Frank_Sumptions_Plans.pdf
http://www.keyportparanormal.com/images/theghostbox_1_.pdf

Now some of the discussions about the device are here:
http://ghosthuntersofamerica.com
http://www.keyportparanormal.com
and for balance the skeptics are here too:
http://www.csicop.org/specialarticles/show/franks_box_the_broken_radio

Me? I am neutral. I will neither confirm nor deny if the device works, though I do have my doubts. But it does make for a potential halloween party concept. Which is why I bring it up. With this item you have a “Seance in a box”- just add batteries. (Imagine the infomercial ads on TV now….) On the other hand- it may have some other uses such as lightning detection or locating stray transients, RF noise sources, etc. I will not say that it will have no uses, I just have my doubts about it working in the manner Frank suggests. But on the other hand, it might work.

Now, if you want to build an electric charge detector/ lightning detector or static charge detector that does work, this item which I did build a number of years ago, does work, and when I had hooked it to a longwire antenna the static charge blew out the JFET after a while, but it did work at least for detecting accumulating charge on the antenna and other things. If you are a ghost hunter and want something incredibly simple for detecting electrical potentials- this is the item There are a lot of things to look at on AMASCI.com too but this one as simple as it is is actually buried under a great many other items and would be difficult to find unless you knew where tolook and what to look for. But build one of these and see what you find with it. “Amaze your friends.” This is also a good project for kids who need a science fair idea.

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

The associated blog for above youtube channel

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

http://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.

Posted in Uncategorized

Construction of a Guitar Amplifier Worthy of the Effort

This post is a diversion from the alternative energy area, but it is about something many can appreciate, and so this post is about building a Guitar Amp, and not just any amp, but an homage to the Fender Vibrolux.

What I began with was a metal chassis for a Fender Hotrod Amp, but it had been stripped of everything. So this was essentially going to be from the ground up. Now, the power transformer and the audio output transformer are usually the two most expensive pieces. I happened to have both from an amplifier that came from a Rockola. That amplifier was a “Type “O””, and it had been converted to a PA amplifier back in the 1960’s, and since I could not find a buyer for the amp as it was, I just stripped that chassis down and set the parts aside for later use. This amp build is that later use.

Not knowing fully the ratings of the power transformer, I made it a point to allow for a different power transformer to be used if this one lacked adequate power- something that proved to be a pointless concern- that power transformer had plenty of power to spare. Armed with the schematic of the orignal amp (Vern Tinsdale’s site had that.) I looked at a number of amps for a basic design to work around, and settled on making a variation of Fender’s “Custom Vibrolux”. A significant portion of that amp is straight from design books of RCA and other tube manufacturers over the years. The major points that are Fender’s design are in part in the tone stack and in part the Vibrato circuit and “C” supply aspect to some extent. This amp I built is a “one of a kind”, and an “Homage” to the Fender Vibrolux. Other amps that I will build in the future will have different tone stacks and effects will be made differently- although the driver circuit for the reverb tank is almost textbook, and in a pinch I could sub in a 6AQ5, 6EH5, 6AR5, etc with just a socket swap and modest circuit changes. Because of this I am not putting up the final schematic. Other amps in the future- certainly, just not this one. If you want to try build you rown, that is up to you, you can get the power and output transformers from Hammond manufacturing and Fender is gracious enough to have many of their amplifier schematics online. I am not linking to them, those are for your own research.

Now to be clear- this amp was not going to be a total ripoff of their design, that was not the intent, but rather this amplifier is an Homage to their design and to see if it could be accomplished with what I had available- with a few important tweeks and differences, their design only gave a starting point, and there have been different vesrions of the Vibrolux since it was introduced in the 1950’s. To say the least, this amplifier is a “one of a kind” largely because many of the parts I used were the only parts I had of that type on hand, and with the PIO’s, most of those vendors who have them in their catalogs in North America are lacking many of the values you would need. Any other amps I build in the future will be different- even if inspired by other amps manufactured by the big name companies, there will be notable circuit differences in what I put together.

Paper In Oil or “PIO” capacitors are in the audio path of my design variant, and effects use polyester or styrene capacitors. Many values differ because of the inventory I had on hand demanded it. I also built up a separate supply board for the “C” voltage- which is a winding in the Fender transformer and the Hammond replacements just taps it from the “B” winding. I also used a 3 wire choke instead of the 2 wire choke Fender used. I also added a wiring fault indicator, wired at the EMI filter I also used that which the original design did not. My output tranformer also had 3 impedance taps- an 8 Ohm, a 4 Ohm, and a 2 Ohm. The external speaker jack is wired in a manner where the plug also changes the impedance tap that connects to the outputs. I used 8 Ohm impedance speakers for the basic testing and the final cabinet speaker- which is hardwired to the amplifier for reliability is a single 12 inch Emminence “Delta 12A” speaker instead of a pair of 10’s the newest rendition of the Fneder Vibrolux uses. I also used numerous terminal strips instead of a “turret board” for assembly, as well as carbon film resistors for longevity and stability.
As things progressedas things looked aboveThings coming along
Because of space needs, the tone controls are ganged for Bass and Treble-with individual volume controls for each input. Both preamp stages are identical with the exception of one having a PIO on input and one having an “Orange Drop” (A type of high quality mylar capacitor that Sprague still manufactures.) on input. The Fender design adds a small bypass cap to the volume control for the second input to make it “bright”- something I ommitted. I also used ceramic octal sockets and the small tubes have a socket with twist lock shield that is spring loaded.

The separate C supply was in a voltage range I did not have working voltages for among my capacitor inventory, so I put 2- 47 microfarad 50 WVDC capacitors in series cutting the capacitance in half but raising my working voltage. Using 2- 220 microfarad 50WVDC capacitors gave me the value for the first capacitance in that supply as well. I also used a full wave bridge rectifier instead of half wave rectification not knowing for sure if I had adequate current available. The 18K resistor is a standard value resistor and is the main current limiting device for the C voltage in the Fender circuit. Now the applied C voltage where it is injected to the audio/effects stream requires the C supply to be positive grounding to the chassis so the C voltage can take the signal grid of the 6L6’s below the chassis potential to cutoff where the slow speed oscillaltion of V5 (on the Fender schematic) modulates that cutoff point creating the Vibrato. Initially, I installed a switch so resistance could be switched into the C supply circuit to bring some range into adjustability with the original value pot I used (which is explained later.)- I did leave it in after some changes mentioned below, but when it is switched into the circuit there is a notable loss in volume. The resistance I selected for best audio effects results turned out to be 470K Ohms in the C- circuit between the supply and the control. Fender indicates in their schematic 55 volts peak to peak- the voltage in mine is different due to the different values used in the Vibrato circuit and the selection of the 470K Ohm resistor was done by ear. It has been a little while since I measured the potential and the amp is well buttoned up now as I write this, but I seem to recall I measured with my meter- about 28 volts. Since the Vibrato worked very well, I left it at that value.

Now, the original chassis initially had a number of holes in it, some I could use as they were, and some I had to enlarge, or just place something over the hole. It had seen one attempt at a homebrew amp before, which did not progress very far, which left the chassis still workable. This time, the chassis would see a final design built upon it.

Chassis

This was what I began with.

bottom view

Bottom view


As the orignal layout of knobs and switches dictated placement of controls, I worked with the original locations as much as possible. Some of the holes were located in a way that made for some innovative thought. As you can see in the images, the 5U4 rectifier and the 6L6GC’s hang down-
tubes down

While the image was taken near the completion, it shows the vertical “down” position of the 5U4 and the 6L6GCs.

they have clips on the sockets to hold them in place. It worked out to be a good decision as the tubes hang down in the airflow of the cabinet. I used a piece of double copper clad fiberglass circuit board as a radiant barrier on the lower board, and there is another on the amplifier back side due to 2 large power resistors which were needed to bring the B voltage down to a level safe for the filter capacitors. This also brought the nominal power of the amplifier close to the Fender Custom Vibrolux. This also brought the power into the output transformer’s “sweet spot” which is important for longevity.
first holes punchedMost holes punchedMain transformers mountedBottom view of transformersThings coming along
*If in the future a different output transformer is used, with changes to the filter capacitors and elimination of 2 resistors (a 1000 Ohm and a 2000 Ohm power resistor visible in the oneimage) in the B circuit- the amp becomes a screamer in excess of 50 Watts into 8 Ohms with a 5U4 because the plate voltage without those 2 resistors is in excess of 510VDC.

Tube complements on guitar amplifiers and Hi-Fi tube amps tend to use 12AX7’s, 12AT7’s and 12AU7’s. There is no difference here- but final selections were not made without trying different tubes in all locations. Especially since the tubes I used for initial testing and troubleshooting were random box grabs of tubes I had on hand. When the new tubes were installed, the amp became unrully where the old tubes actually sounded great. This however led to meticulous inspections of solder joints, and componet values. The initial impedance matching transformer I used for the output to the Reverb tank seemed to be a new old stock piece that had never been used- it turned out that as B voltage increased the transformer developed an open circuit. So to replace that I dug through salvaged transformers and located one for a 6AQ5/6EH5 to 8 Ohms. (The actual realized impedance on the primary of an audio transformer is dictated by the impedance or load on the secondary. Something many people forget.) The solder joints were fine, but one terminal where a nickel plated component lead was wrapped in needed some attention to actually look reasonable and reliable. Ultimately when everything was done, Reverb is clean- no culvert sound to it like some cheap stereo reverbs can sound- this was clean and gave good sustain time.

A project like this is usually best done in stages. Heath made their kits this way for a good reason. If you forgot a wire connection (and I did forget one wire) it was located by simply compairing the stages in the order they were assembled, and the missing wire became glaringly apparent as it was one that transitioned from one stage of construction session to another stage of construction session. These things happen. The key is finding it in a timely fashion, which I did.

Now the reason the new tubes were so unruly was due to a couple of factors that added together. The foremost issue was the B voltage. I had the amp operational with high B voltage, well above that of the Rockola design. I added in resistance to bring that voltage down to a point where the filter caps would not be stressed. If I had left it as it was, the B voltage would have been 515 volts. Too high for the caps I had used to be left that way, but one option was to get some new caps and just live with it, however the output transformer would be severely stressed and likely to fail sooner rather than potentially never. With the resistors added in, things began to settle down. The remaining issue was the effects.

The inter-relationship of the values of the controls for vibrato speed and intensity are fairly critical. Initially I used a 500K Ohm pot for the intensity instead of 250K Ohms. The higher value did allow for adjustment, but was not stable at the low end, and tended to have a rather “poppy” sound over much of the range. This even after the C voltage was “dialed in” experimentally intot he range of Fender design value. If I had set up substitution boxes on the 6L6 Grid Resistors, I could likely have dialed in a value that was less “poppy”, but it likely would still go into low frequency feedback. However the Vibrato also seemed very weak. It was not helped by my using an 82K Ohm resistor for the cathode resistor of the tube in the Vibrato section that was fed by the C voltage.

At that point I dug out my buckets of pots to locate a 250K Ohm “Linear Taper” pot. While I could have used an audio taper pot, that would have meant most of the adjustments would be in a narrow adjustment range and difficult to find the “sweet spot”. The original is a linear type for a reason.

So with the 250K Ohm Linear taper pot in place, things came to life. Reverb which seemed to me to be muddy and lackluster, began to be heard clearly. The Vibrato as well came to life. But I needed to reselect a resistance value to get the C voltage back in range as that now dropped to about one third of the C voltage it was before. Mind you, the C voltage is derived from a discrete 56 volt transformer, which means on a scope- the peak voltage is actually close to 80 volts. So I needed to dial that down to about 33 volts (as measured with a meter.) and was found experimentally with a substitution box again. Or rather back “up” with the new control. However when everything was sorted out and done, Vibrato was clean and clear.

With that though the amp was still a bit “poppy”, so I started experimenting. One of the results that really opened things up and calmed things down was at C10 on the Fender schematic. Instead of a silver mica capacitor of 500pf, I used 2-0.001microfarad PIO capacitors in series (to raise the working voltage again) and it is in between those 2 capacitors where I added in a 15K resistor and 1000pf ceramic capacitor to ground in the way a bypass filter works- this alone ultimately removed a great deal of the “pop” and settled the amp down to a point where it was actually a nice clean sound.
bottom view in progress

tubes down

While the image was taken near the completion, it shows the vertical “down” position of the 5U4 and the 6L6GCs.


It was at that point where selecting the best sounding 12 inch speaker was made. As a baseline, I used a vintage Jensen Alnico magnet speaker from a decent vintage Newcomb phonograph. There was a slight difference between that and the modern Jensen 12 inch “P12Q” “Ted Weber” series sepaker, but they both still sounded slightly “shrouded”-for this amp it was much too similar to low end speakers on a low end stereo, but not quite as bad as those as the Jensens are a top shelf speaker, they were just not right for this particular amplifier. It was then when I tested the Emminence “Delta 12A” 12 inch guitar speaker. With a massive magnet that barely cleared the transformers of the amp, this one had plenty of potential for issues with the audio transformer, but that was magnetically shielded originally, so no issue when fired up completely assembled. If the individual I made this one for needs some additional gain, there are some tweeks I can do that may be worth looking into later, but for now- Let the good times roll.
ready for ribbon
Ready to roll.  The one speaker opening is left open for airflow.

Ready to roll. The one speaker opening is left open for airflow.

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

The associated blog for above youtube channel

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

http://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.

Posted in Amplifier repairs, Auditorium equipment, Homebrew, Project, transformers, Uncategorized | Tagged , , , , , , , ,

Table Saw Repair

I am crossposting this from one of my other blogs because it is an electrical repair of a fairly common household tool. This can save you money if you happen to have one of these saws, or similar.

A While back, my old Sears 10 inch Table saw “gave up the ghost”, it simply stopped and flipping the switch back and forth a number of times did not get any noise from the motor. So I swapped a Delta “Super 10” Saw onto the base and ran that one for a while, until the motor capacitors failed. This being a tight budget situation required some thought on the matter as to which one to repair first. The Sears saw got the nod because I located a scrap Sears 10 inch saw that had a different top on it, but just happened to be the same motor and arbor mechanism. And having a decent table saw you can move around is almost an essential for a home renovation as well as for other projects.

The image shows the location of the 6 screws on the edges circled in red that retain the aluminum panel, there may be one or two others on that panel as the saws did have some variability. The two screws holding the protractor do not need removal as they only have a quick nut behind them and do not secure the panel in any way, so they can be left alone. The 2 screws circled in blue hold the switch.

front panel

The screws to remove the panel are circled in red.

After some initial disassembly to get at the wiring for checks, which entailed removing 8 Phillips head screws that held the aluminum plate (as well as the sheet metal end of the saw to the rest of the base). The aluminum plat is what the switch itself attaches to with 2 philips screws of about a #6 size. The switch will not come out unless the yellow safety tab is removed. Slipping the two wires off of the switch freed the plate which was set aside for the moment as some cursory checks and a wiring diagram were written down. That aluminum plate itself- which once removed revealed decades of accumulated sawdust and essentially the compact assembly of the recess for the switch, the motor start capacitor, the thermal motor fuse/reset switch and the magnetic starter. The metal bracket under one of the thermal reset screws just retains the magnetic starter in place

Saw wiring Schematic

Wiring Schematic for Craftsman Saws since the 1960’s. Rigid Saws will be similar.

Once the schematic was finished, it was simple matter of checking with an Ohmmeter the various potential culprits, which actually turned out to be the first item I checked- the switch. The parts saw was promptly pulled apart and that switch removed and once checked- it was revealed it too had issues, and was the most probable reason the donor saw was scrapped. This is a fairly general schematic as far as applications go. If you happen to have a newer power cord wired to an Asian or European wiring standard, double check the cord leads to be sure they correspond to the correct plug prongs, but most of those types will use the Brown wire for “hot” and the Blue wire for “Return” with the green wire with yellow stripe as the ground wire. In the US, the Black wire is the “Hot” lead and the return is the White wire.

However, this being a budget situation, I first tried some contact cleaner- I found later this was not even worth the effort, and hindered the efforts to clean out the sawdust. With the switch still showing no continuity when “on”, I decided first to take apart my old switch, which was melted from a fire (I actually bought the saw for the price I did because it had been too close to a fire, and it showed- which made people not take a second look at it in spite of the price at that garage sale. The fellow was pleased that the saw was going to good home- mine, and that I was not afraid of the melted nature of the cord or the switch and knew how to deal with them safely. I did get my money’s worth of work out of it initially before it started to act up. Once I had the original switch taken apart, it was actually very simple in design compared to some I have taken apart over the years and saw how easy it would be to effect repairs on the switch.

The Switch Taken Apart

The switch taken apart

The one thing I would suggest if you decide to try this yourself, first put the switch in the refridgerator or freezer to chill it and thicken the grease that holds in the plastic pin which is missing in the photo. The image is missing the plastic button portion that rides against the moving contact. Chill the switch first and work quickly. you should not lose that button. Doing the repair outside is taking a risk and I admit I got lucky. The button must have shot out of the switch when it warmed inside of the solar gazebo where I parked the box of spares for the moment.

The problem is sawdust filters into the switch in spite of that foam seal. Both switches were fully packed with sawdust. Now getting the switch apart is easy, with a diagonal cutter or small screw driver, just bend the corner tabs that hold the rocker portion to the lower phenolic portion- bend them out enough for the tabs to be clear of the phenolic shoulder each anchors to. Gently peel the foam seal off the phenolic and tap out the saw dust. Compressed air might be a consideration if and only if you have the button and the copper piece that rocks to make the switch contact. It is that missing piece that rides on the back side of the rocker to make and break contact within the switch. As you can see, this one is quite pitted and therefore not used, since the original switch had better contacts, I took the best parts of both switches and combined them into one switch. If you are only dumping out sawdust, this whole process takes less than 5 minutes. Some degree of pitting is normal, but there is also a point where the pitting is just too extensive to even consider reuse. Dressing the contact with a “point file” might get some additional life out of the switch, but at some point an inevitable replacement will be needed. The switch is rated for 15 Amps, so you can replace it with a heavier switch to extend the life of the contacts of the new switch.

On reassembly, the rocker just sits on the pivots- make sure the botton contact is over the button contact on the switch body. Then reapply the foam seal and gently place the rocker assembly over the switch body- it is self aligning in most respects so all you need do once the top is in place on the body is push the tabs back over their resting places and the switch is ready to go back into service.

Since my original cord was melted, and I had a replacement cord, I simply undid the strain releifs and pull out the old cord. to undo those strain reliefs used, it is just a matter of squeezing the small tab that is visible towards the other portion of the strain relief that surrounds it with a plier or water pump plier just enough to allow for the relief to be rocked out of it’s hole. The replacement cord, which was salvaged from a plastic based Craftsman saw, just slipped into place. Both were 16 Gauge 3 conductor cords, so no issues there. If you replace with something that came from a different tool or source- make sure it is at least 16 gauge- 14 will work as will 12 gauge. If you are running the saw on an extension cord and simply want to incorporate that as the power cord- locate suitable strain reliefs- you will need 2, and enlarge existing cord routing holes and install cord. Then install the strain reliefs leaving a little slack between the 2 strain reliefs. If you are running a 25 to 50 foot cord- 12 or 10 gauge conductor will be a really good idea.

Reassembly is straight forward, the 2 slotted screw that hold the thermal reset fuse have a small brakcet that holds the mag starter in place. the screws only need to be snug- just enough to hold things in place while you are doing assembly. Now, neither saw had any issues with the mag starter or the start capacitor- if the start capacitor had vented at all, there would be the aroma of Hydrogen Sulphide (rotten eggs.). If a capacitor fails on startup, you will have large amounts of smoke billowing out of the saw cabinet in the vicinity of the switch. If there is a problem with the “Mag” starter, or if it gets wired incorrectly, the motor will run slow, noisy and hot. For this reason: only undo the wires that attached to the item needing immediate repair. The only other caveat just make sure your blade angle indicator is not stuck under the aluminum panel when reattaching the aluminum panel to the saw.

The industry part numbers for some of the parts are listed on the image, and these should be simply industry numbers in most cases- not Sears part numbers, so they can be located through motor repair shops, some online vendors, etc.

I did power the saw up after putting the saw back on it’s original base (4 bolts) and it started right up as if nothing had gone wrong with it. Considering the original handles for blade angle and blade height had melted off, I saw it as a good time to pull the handles off the donor saw and install them on the good saw. The correct handles made all the difference in ease of use, but if you are having some trouble with either adjsutment being stiff, just apply some motor oil to the threads of each adjuster and crank them to their extremes, and as always- store a table saw with the blade fully retracted below the table surface.

Since my saw dates from the 1970’s, I expect the saw should last at least another decade or two before needing work on the switch again. The capacitors usually have a date code inked on them somewhere, so if you really wanted to know the age of the saw, you can figure your saw was likely made about 6 months after the date code on the capacitor.

If the saw squeals on startup- the bearings are dry. The Sears 10 inch saws, the Rigid table saw of similar design and the Delta “Super 10” are direct drive motors- in other words the blade arbor is the motor shaft. (Some people do not like this approach, but it saves weight and costs and is reasonably durable. They may not be adequate for a large manufacturing plant, but houses have been built with less of a table saw or none at all.) The bearings are not within the scope of this post, but if you pull the end bells off the motor, you can see the bearings. If they just make noise, but are still smooth in rotation, you could try regrease the bearings (if ball bearings) by gently pulling the dust seals off one side of the bearing with a flat dental pick or small screw driver- use care not to damage the inner race sealing lip and then repacking them much as you would a wheel bearing- use a short fiber grease or one with Molybdenum Disulphide and pack it full -after applying some solvent to remove the old grease residue. Once repacked, then it is only a matter of straightening the old dust seal and slipping it back on the bearing once you are sure there is no damage to the inner seal lip that rides on the inner bearing race. Never apply compressed air to a “dry” bearing that both races are secured against rotation or damage that can affect the life of the bearing can occur.

Older saws sometimes use ball bearings to support the arbor, and these are usually marked on the outer race as to what their part number is if you choose to just replace them, and then it is only a matter of slipping them off the shaft or out of the arbor casting- which is aided by a wood mallet or plastic faced hammer. Older saws used sleeve bearings/bronze bushings, which if they run dry will make noise, and these are just a matter of a few well placed drops of oil to take care of them in most cases- unless there is too much radial play. In that case those need to be driven out and new sleeve bearings of the correct size gently driven in. There should be minimal axial play (side to side or end to end of the arbor shaft), but there should be about 0.010 inch clearance so the arbor can spin freely. This is adjusted by loosening the arbor pulley and moving it closer or away from the arbor casting.

Further adjustments and tweeks will likely come later as they take some time to perform them correctly, and my saw is still in adjustment, plus some of the adjustements that can be made on other saws cannot be made on this saw due to how it was manufactured.

http://www.youtube.com/channel/UCdjcUtAAJ-CZVwaabB6SBpA

The associated blog for above youtube channel

http://altenciruits.wordpress.com/
The main blog.
the begining point place to start

https://altencircuits.wordpress.com/
The tangential blog.

http://passivesolarproject.wordpress.com/
The passive solar blog- outgrowth from some projects of mine.

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