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Post by antigua on Nov 30, 2019 14:23:10 GMT -5
I bought wax last year in order to try experimenting with wax potting, but I was slow to get around to it because I have a gas stove and I was worried about starting a fire with the wax. I was also skeptical that wax would make much difference. Then philbard conducted a test here guitarnuts2.proboards.com/thread/8736/effect-wax-potting-resonant-peak showing a significant increase in capacitance, so I've taken the time to figure out how to safely melt wax and do this experiment in order to see if I would get similar results. I have an unpotted Strat pickup I wound to 8,000 turns, about 2.5H inductance, and 103pF capacitance prior to wax potting. After an hour of wax immersion in beeswax, and then cooling, the capacitance ended up at 162pF. I also tested microphonics be tapping on the pickup with a wood spoon dozens of times, and recording the peak output. Unfortunately, since this is the first pickup I've wax potted, I didn't realize how rapidly the wax would permeate the coil, and in fact I was led to believe that without some sort of vacuum system, the coil might not fully penetrate at all. But in fact it appears that within ten minutes the coil was almost fully permeated by wax. With a coat of wax, the pickup only became slightly less microphonic, but with but once permeated, the pickup showed no trace of being microphonic at all. Another take away I get from this is that it appears that the coil is fully penetrated, despite having no vacuum potting device. This type of Strat pickup has a hole in the center, so wax is able to enter the coil from the inner center as well as from the outside. I've been interested in seeing how well denatured alcohol might remove the wax from the pickup, so I'm planning to immerse this test pickup in denatured alcohol and measuring the outcome. Once caveat with my test pickup is that the coil is not especially tight, as can be seen in the picture below, due to being hand tensioned. That might have allowed for 1) a higher degree of microphonics when unpotted, and 2) a more rapid and thorough penetration of the liquid wax. With similar production Strat pickups, I've usually measured capacitance between 85pF and 150pF, usually all are said to be wax potted. I don't know of any production Strat pickups that are not wax potted. Some pickup makers claim to "lightly" wax pot their pickups, it might be that the pickups with lower capacitances are in fact "lightly potted", while pickups with higher capacitance are more thoroughly potted. LCR Testing:The wax is beeswax, I heated it in a pouring pot, set in heated water over a hot plate. The temperature held at 205 degrees Fahrenheit. These are the reading from the DE-5000 for different time periods in the wax. For inductance, the meter is set to 100Hz in series mode, for capacitance, its set to parallel mode at 100kHz. No wax:
L: 2.492 H C: 102.95 pF R: 6.045 kohms
Quick dip:
L: 2.514 H C: 101.46 pF R: 6.225 kohms
1 minute
L: 2.503 H C: 104.64 pF R: 6.172 kohms
10 minute
L: 2.478 H C: 147 pF R: 7.113 kohms
30 minute
L: 2.468 H C: 150 pF R: 7.198 kohms
60 minute
L: 2.474 H C: 149.25 pF R: 7.404 k ohms
60 minute (after cooling to room temp)
L: 2.504 H C: 162 pF R: 6.016 k ohmsThe measurements show the copper resistance increases from 6k to 7.4k as it became hotter. The wax was holding at about 205 degrees Fahrenheit, so the copper coil was must have been about that temperature as well when it was measuring 7.4k ohms resistance. From unpotted to fully saturated, the pickup's capacitance increased from 103pF to 149pF. While still hot, the capacitance was measuring 149pF, but after cooling, the capacitance measured 162pF, most likely due to the wax contracting, causing the space between the wire turns to shrink. It appears the inductance dropped slightly as the potting progressed, but then rebounded after potting was complete and it had returned to room temperature. This is the bode plot for five stages of testing: The peaks are clustered because the majority of change happened fairly rapidly between 1 and 10 minutes of immersion. I will do another test with more time divisions between 1 and 10 minutes to measure the rate of penetration during that time period. The slight variation in Q factor caused by the copper wire becoming more resistive at high temperature is also apparent. Microphonics testing:Quickly dipping the pickup in wax result in it's being covered in a thick layer of wax, as did leaving it immersed for 1 minute. The pickup itself was still very cool, so the wax hardened on the outside of the pickup. The capacitance readings up to 1 minute suggest the coil itself was still wax free. The wood spoon tapping showed amplitudes of 46dB, and it dropped to 40dB with wax coating the outside of the pickup. At ten minutes, according to the capacitance readings, the wax almost fully permeated the coil, and the microphonic output went away almost completely, just above the noise floor. After 30 minutes, there was absolutely no output voltage above the noise floor as a result of hitting the pickup with a wooden spoon, the coil is not microphonic at all.
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philbard
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Post by philbard on Nov 30, 2019 16:07:57 GMT -5
Very interesting. This is a larger fall off in resonant peak than I was expecting based on my test, but mine was done on just the coil, no magnets or other metal installed. I also used pure paraffin as opposed to beeswax. Seems to me that much drop would produce a significant change in the pickup's behavior when installed in the guitar. I look forward to finishing my test to be able to hear the results and also hearing others' feedback on this one. Thanks!
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Post by antigua on Nov 30, 2019 16:46:40 GMT -5
Very interesting. This is a larger fall off in resonant peak than I was expecting based on my test, but mine was done on just the coil, no magnets or other metal installed. I also used pure paraffin as opposed to beeswax. Seems to me that much drop would produce a significant change in the pickup's behavior when installed in the guitar. I look forward to finishing my test to be able to hear the results and also hearing others' feedback on this one. Thanks! And easy way to test is to simply jump the guitar jack hot and ground with a 47pf cap an see if you notice a change in tone. I personally haven't been able to hear a difference with such small value caps.
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philbard
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Post by philbard on Nov 30, 2019 20:25:28 GMT -5
And easy way to test is to simply jump the guitar jack hot and ground with a 47pf cap an see if you notice a change in tone. I personally haven't been able to hear a difference with such small value caps. Yes, assuming that capacitance is the only thing that is changed by waxing, which I suppose is likely.
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Post by antigua on Nov 30, 2019 20:35:02 GMT -5
And easy way to test is to simply jump the guitar jack hot and ground with a 47pf cap an see if you notice a change in tone. I personally haven't been able to hear a difference with such small value caps. Yes, assuming that capacitance is the only thing that is changed by waxing... Well, if you're interested in capacitance as a cause, the cap will suffice, just remember that you have to have the volume control full open in order for the test to be valid. If the other change youre referring to happens to be microphonics, note the results of this test. We have a rather loosely wound pickup, being hit with a wooden spoon over and over again, and the highest transient voltage it produced was only double the voltage of the ambient noise level. If you want to test this yourself, maybe through other means, just open the spectrum analyzer in the Velleman PSCU200 software and set it to persist mode, subject the coil to some sort of force in order to induce a voltage and observe the voltage spikes, then select "copy" to save a screen shot to the clipboard.
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philbard
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Post by philbard on Nov 30, 2019 20:47:54 GMT -5
Thanks, I was wondering how that test was performed.
BTW, many people caution against going over about 150 degrees fahrenheit during potting or risk deformation of the bobbin. Are you aware of this and is it possible to see if any occurred? The reason I bring it up is that I'm wondering if it could conceivably change the physical dimensions of the coil in a way that might affect results. Perhaps not so much of a risk in a Strat style bobbin as with a Humbucker, and perhaps also I'm splitting hairs a bit too finely.
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Post by thetragichero on Nov 30, 2019 21:06:35 GMT -5
thanks antigua and philbard for these! had always wondered if I'd been potting for long enough i use a small crock pot with boiling water and a coffee can filled with a mixture of beeswax and parafin
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Post by stratotarts on Nov 30, 2019 22:45:59 GMT -5
Thanks, I was wondering how that test was performed. BTW, many people caution against going over about 150 degrees fahrenheit during potting or risk deformation of the bobbin. Are you aware of this and is it possible to see if any occurred? The reason I bring it up is that I'm wondering if it could conceivably change the physical dimensions of the coil in a way that might affect results. Perhaps not so much of a risk in a Strat style bobbin as with a Humbucker, and perhaps also I'm splitting hairs a bit too finely. I think the resistance measurements show that this didn't happen. If the coil was stretched, the resistance would increase. BTW I potted with 80/20 paraffin/beeswax at about 180. It's true some plastics shouldn't get too hot.
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Post by antigua on Dec 1, 2019 1:01:36 GMT -5
Thanks, I was wondering how that test was performed. BTW, many people caution against going over about 150 degrees fahrenheit during potting or risk deformation of the bobbin. Are you aware of this and is it possible to see if any occurred? The reason I bring it up is that I'm wondering if it could conceivably change the physical dimensions of the coil in a way that might affect results. Perhaps not so much of a risk in a Strat style bobbin as with a Humbucker, and perhaps also I'm splitting hairs a bit too finely. With a plastic bobbin that might be a concern for sure. The fiberboard seems to be highly durable, being a fibrous material. I suppose I should check the gauss of the magnets, though I think alnico is stable up the very high temps.
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Post by stratotarts on Dec 1, 2019 8:16:29 GMT -5
Using a rectangular coil inductance calculator, I get the result that if the coil width increased from 8mm to 9mm without any change in area, the length would have to shrink from 50 to 44.45mm and the inductance would increase by 3.3%. I'm assuming that the coil can't stretch overall very much due to the relatively high tensile strength of copper. This is another reason why I don't think the temperature could have affected the results very much.
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Post by antigua on Dec 1, 2019 16:00:36 GMT -5
Various websites on the 'net claim the max operating temperature of vulcanized fiber board is anywhere from 250 up to 400 degrees Fahrenheit, so it should be impervious to deformation due to wax potting.
I can't find info on the melting point on butyrate, but I see a data sheet stating that ABS would deform at 160F, so holding the wax close to 150F makes sense, and seeing as that's close to the melting point of bees wax, that must be a little tricky. Given that paraffin has a lower melting point, and is cheaper, why not just use 100% paraffin all the time? Why do I hear about pickup makers mixing beeswax and paraffin together?
Here's another question I should try to answer, did I get especially rapid penetration due to the high 205F temp, and would a lower temp result in a slower uptake?
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philbard
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Post by philbard on Dec 1, 2019 18:16:28 GMT -5
Various websites on the 'net claim the max operating temperature of vulcanized fiber board is anywhere from 250 up to 400 degrees Fahrenheit, so it should be impervious to deformation due to wax potting. I can't find info on the melting point on butyrate, but I see a data sheet stating that ABS would deform at 160F, so holding the wax close to 150F makes sense, and seeing as that's close to the melting point of bees wax, that must be a little tricky. Given that paraffin has a lower melting point, and is cheaper, why not just use 100% paraffin all the time? Why do I hear about pickup makers mixing beeswax and paraffin together? Here's another question I should try to answer, did I get especially rapid penetration due to the high 205F temp, and would a lower temp result in a slower uptake? Yeah, I always stay at about 145 as I use plastic. And as mentioned before, paraffin, so I don't need higher temperatures. I would guess that the viscosity of beewax is lower the higher the temperature, and maybe you got a little better penetration, but since there are holes in your bobbins that also would speed things up. My buckers have only the small ones at one end for the start wire.
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Post by antigua on Dec 1, 2019 22:36:04 GMT -5
Attempting to remove the wax...I've looked into the possibility of using various solvents to remove wax, the 'net has lots of suggestions, such as boiling water, heated vegetable oil as well as using various solvents. Boiling water seemed like the least destructive way to go, so I tried submerging the beeswax pickup in boiling water for five minutes. There was no change, so I submerged in for a full thirty minutes. Inductance and DC resistance is unchanged, so at the very least the pickup hasn't been damaged. But here's the crazy thing, the capacitance increase by an even larger amount, now reading 232pF @100khz in parallel mode. Removing beeswax with boiling water
Inital values with beeswax:
L: 2.504 H C: 162 pF R: 6.016 k ohms
Boiled for 5 mins in water:
L: 2.494 H C: 232 pF R: 6.024 k ohmsFrom the reduction of the Q factor, I would have suspected that there might have been internal shorts in the coil causing eddy currents damping, but the DC resistance is virtually unchanged. I realize the Q factor will change when the ratio of inductance to capacitance is altered, but this drop in Q seems extreme. Wax definitely came out of the pickup. The wire now moves freely when touched, and there was a healthy amount of wax floating on the surface of the water. As further evidence that wax vacated the coil, its not only microphonic, but it appears that it's actually more microphonic now that it had been prior to wax potting. The cluster of blue on the bottom is the noise floor, the cluster of blue on top is the voltage from impacting the pickup with a wooden spoon. I can't think of an obvious reason for the capacitance to now be so much higher. It might be that the boiling water thinned out the insulation coat of the magnet wire, or further decreased the amount of air and space between the turns of wire. The bad news is that the process made the capacitance higher, when I had hoped this might be a means of restoring the pickup to it's original pre-wax potted values. Also note that the top part of the fiber board bent upwards towards the edges slightly. I suspect that the fiberboard bent a little while it was in the hot wax for 30 minutes, but then bent even more after having been in the boiling water for 30 minutes. In the picture above, after all the potting was completed, I think I see a very slight concave in the top of the bobbin. It might be possible, at low temperatures, holding the water at 150 Fahrenheit, or by submerging the pickup in warm denatured alcohol, to remove the wax without also causing any of this apparent damage to the fiber or or the coil itself. As a side experiment, I tried placing paraffin and beeswax in heated denatured alcohol, the beeswax remained solid, but the paraffin turned to liquid in the heated denatured alcohol, so I'm interested in attempting to remove paraffin from the coil this wax as soon as a I have a paraffin potted pickup. I'd like to find out what companies like Fender and Gibson use for wax potting, so that if some scheme for subtracting wax is found, we'd know if it might work with Fender or Gibson pickups.
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Post by reTrEaD on Dec 2, 2019 11:15:06 GMT -5
I can't think of an obvious reason for the capacitance to now be so much higher. It might be that the boiling water thinned out the insulation coat of the magnet wire, or further decreased the amount of air and space between the turns of wire. While it's possible the high temperature caused the insulation to become thinner, another thought worth examining is the fact that water has an extremely high dielectric constant (roughly 80!). So even a tiny amount of water remaining between the windings *might* have a profound effect. idk, just guessing here. If you have access to a vacuum chamber, perhaps some time in there would lower the boiling point of water and help the drying process?
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Post by antigua on Dec 2, 2019 11:51:04 GMT -5
I can't think of an obvious reason for the capacitance to now be so much higher. It might be that the boiling water thinned out the insulation coat of the magnet wire, or further decreased the amount of air and space between the turns of wire. While it's possible the high temperature caused the insulation to become thinner, another thought worth examining is the fact that water has an extremely high dielectric constant (roughly 80!). So even a tiny amount of water remaining between the windings *might* have a profound effect. idk, just guessing here. If you have access to a vacuum chamber, perhaps some time in there would lower the boiling point of water and help the drying process? That's a great point, I'll see if I can dry it out. Edit: you were right, it must have been water. About 12 hours later it's reading 162pF. That happens to be the measurement after the wax potting occurred. This introduces the possibility that the wax wasn't necessarily causing the increase in capacitance, but rather maybe the high heat deformed the insulation coat. I'll put in bag with a desiccant and see if I can dry it further. The boiling water really did seem to clean the wax off of the outer portion of the coil, and the restoration of microphonics indicates that many of the windings are once again free to move around, but I will try cutting into the coil as soon as I'm ready for it to be destroyed, and see how much wax remains within the windings. I should have tried weighing the pickup before and after, but I forgot. I will try this experiment again with paraffin, and I'll try to correct these issues.
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Post by antigua on Dec 2, 2019 15:38:03 GMT -5
After hours of drying, the pickup's capacitance remains at 162pF. This could mean a few things, 1) that a lot of wax and/or water remains deeper within coil 2) that the wax is/was only partly responsible for the change in capacitance, and that maybe the coil's being subject to heat is the greater cause of change, or 3) some combinations of all of the above that just happens to match the capacitance of an earlier physical state. I'm going to try "cooking" a pickup just to see if the heat alone is a cause of increased capacitance, presumably due to the magnet wire insulation deforming.
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philbard
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Post by philbard on Dec 2, 2019 23:50:21 GMT -5
After hours of drying, the pickup's capacitance remains at 162pF. This could mean a few things, 1) that a lot of wax and/or water remains deeper within coil 2) that the wax is/was only partly responsible for the change in capacitance, and that maybe the coil's being subject to heat is the greater cause of change, or 3) some combinations of all of the above that just happens to match the capacitance of an earlier physical state. I'm going to try "cooking" a pickup just to see if the heat alone is a cause of increased capacitance, presumably due to the magnet wire insulation deforming. Admirable the length you are going to to figure this out. Thinking about it, I suppose its possible that some water is trapped within the wax and will not come out unless it is melted again. Hard to predict, but perhaps when you eventually cut it open it might be a good idea to blot it with a paper towel to see if any water shows up from pockets deep within.
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Post by antigua on Dec 3, 2019 1:33:42 GMT -5
I left the potted pickup and a new test pickup in the oven for an hour at 220 degrees Fahrenheit in order to see if heat alone might cause the capacitance to change, maybe due to deforming the wire insulation. The result is that the potted pickup's capacitance dropped from 162pF down to 155pF, and the unpotted pickup's values are all unchanged. The potted pickup also appears to be only about half as microphonic as it was before. There is also a very small sliver of wax pooled at one end of the coil, but the outer layer of the coil still shows not evidence of there being wax.
Based on this evidence, I'd theorize that...
- boiling the coil in water only managed to remove wax for the outer portion of the coil, but most of the wax remained. - the boiling water replaced the wax in the outer portion of the coil, causing the capacitance to increase to over 230pF (good observation reTrEaD) - once the water evaporated from the coil, the capacitance returned to what it had been, after potting but prior to boiling - heating the pickup to 220F for an hour caused a tiny amount of wax to leave the coil, but most of it remains
The trick might be to heat the coil in a thinner liquid, such a heated soapy water, or heated alcohol. Heated denatured alcohol makes short word of paraffin, but beeswax is a little more tricky. Heated vegetable oil might work, but it has a dielectric constant similar to wax, and the vegetable coil could get trapped in the windings, and then I would have to find a way to remove the oil.
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Post by b4nj0 on Dec 3, 2019 3:43:45 GMT -5
Has the thought of trying an ultrasonic bath crossed your mind? They sound as though they'd be a bit techie and expensive, but they can be had for very low dollars on eBay, priced dependent upon capacity and we'd only need a small one for this purpose. There's a cleaning fluid for them too but we don't want to introduce anything else into the mix. Jewellers use them to clean tiny crevices in jewellery. Horologists use them for wristwatch parts too. Just a thought.
e&oe ...
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Post by ms on Dec 3, 2019 10:14:39 GMT -5
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Post by antigua on Dec 3, 2019 10:51:50 GMT -5
Has the thought of trying an ultrasonic bath crossed your mind? They sound as though they'd be a bit techie and expensive, but they can be had for very low dollars on eBay, priced dependent upon capacity and we'd only need a small one for this purpose. There's a cleaning fluid for them too but we don't want to introduce anything else into the mix. Jewellers use them to clean tiny crevices in jewellery. Horologists use them for wristwatch parts too. Just a thought. e&oe ...Very interesting, I wasn't aware of these things. I think it would have to have built-in heating in order to melt the wax, and I see some have heaters, but it looks like they max out at 140 to 150 Fahrenheit. I would probably have to heat the solution up externally and then add it into the tank. It looks like they cost as little as $40, I might pick one up if nothing more conventional works out. Apparently they are pretty harsh cleaners though, I think there might be a chance it could destroy the fine wire or erode the insulation on the wire.
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Post by antigua on Dec 3, 2019 10:53:18 GMT -5
The capacitance jumped from 149pF to 162pF as a result of cooling alone.
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Post by antigua on Dec 3, 2019 22:22:49 GMT -5
I left the potted pickup in the oven for about 10 hours at 190 degrees to see if any wax might drain out over time, but it looks like the surface tension of the wax is such that it remains locked into the windings if nothing is pushing it out.
If the high capacitance it's enough evidence that most of the wax is still within the coil, another tell is that the coil doesn't easily compress between the finger as it did before potting. I ordered a high precision scale, and before the next pickup is potted I will weight the pickup before and after to see what amount of wax it takes in by weight, and more easily determine how much has come back out.
The top part of the fiberboard, which had become concave due to high heat wax potting, flattened out straight again, but there is now a sliver of space between the coil and top piece of fiber board.
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yanyan
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Post by yanyan on Dec 6, 2019 3:28:31 GMT -5
I left the potted pickup in the oven for about 10 hours at 190 degrees to see if any wax might drain out over time, but it looks like the surface tension of the wax is such that it remains locked into the windings if nothing is pushing it out. If the high capacitance it's enough evidence that most of the wax is still within the coil, another tell is that the coil doesn't easily compress between the finger as it did before potting. I ordered a high precision scale, and before the next pickup is potted I will weight the pickup before and after to see what amount of wax it takes in by weight, and more easily determine how much has come back out. The top part of the fiberboard, which had become concave due to high heat wax potting, flattened out straight again, but there is now a sliver of space between the coil and top piece of fiber board. Very interesting. Given the tenacity of the wax to remain in the coils despite high heat and boiling, i'm wondering about what people say about old wax in an old pickup eventually cracking and causing the pickup to become microphonic. Can we actually say we've disproved this? Assuming, of course, that the pickup wasn't tinkered with in any way, the cover wasn't removed (thereby allowing the old wax to move and shift), etc.
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Post by antigua on Dec 6, 2019 14:06:34 GMT -5
I left the potted pickup in the oven for about 10 hours at 190 degrees to see if any wax might drain out over time, but it looks like the surface tension of the wax is such that it remains locked into the windings if nothing is pushing it out. If the high capacitance it's enough evidence that most of the wax is still within the coil, another tell is that the coil doesn't easily compress between the finger as it did before potting. I ordered a high precision scale, and before the next pickup is potted I will weight the pickup before and after to see what amount of wax it takes in by weight, and more easily determine how much has come back out. The top part of the fiberboard, which had become concave due to high heat wax potting, flattened out straight again, but there is now a sliver of space between the coil and top piece of fiber board. Very interesting. Given the tenacity of the wax to remain in the coils despite high heat and boiling, i'm wondering about what people say about old wax in an old pickup eventually cracking and causing the pickup to become microphonic. Can we actually say we've disproved this? Assuming, of course, that the pickup wasn't tinkered with in any way, the cover wasn't removed (thereby allowing the old wax to move and shift), etc. Wax is used to immobilize both the coil as well as other parts that can vibrate, such as the covers and bases. There is no way that dried out of wax will cause the coil to become microphonic, because in that cases it's the mere presence of the wax, not the adherence that makes the coil immobile. Any substance that is viscous or solid that displaces air within the coil can cause it to completely lose its microphonic quality. But in the case that the wax is functioning as a glue, adhering to the cover or the base plate, if it dries out it might detach from the parts, which are free to move around and cause feedback. This often happens with Tele base plates that are held in place by wax. When the wax dries out, air comes in between the pickup and the base plate and it becomes microphonic. It can be fixed by just reheating the wax.
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