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Post by reTrEaD on Mar 17, 2012 20:36:39 GMT -5
around 1/4 pot resistance plus a bit. Thanks, John. I'll edit that in. +1 for keeping me honest. |
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Post by yakkmeister on Mar 17, 2012 23:49:06 GMT -5
Ok, so I have done the test ...
With my DMM in the 200k Ohm scale I got a reading of 37.2.
That should mean 37.2k ohm, right? (it's been a while ... lol!)
Seems a bit high for 2 s/c's ... Dano p/ups tend to go between 4 - 8k ohms DC... I would have expected max to be around 20, accounting for the extra wire?
Turning the volume pots one at a time then both down to full-off, I have no change whatsoever in the reading, ditto with the tone pots.
This totally looks like a short somewhere - completely bypassing the pots altogether...
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Post by sumgai on Mar 18, 2012 0:39:51 GMT -5
yakky, A short across the pots (either of them) would also be a short across the pup(s) - you'd get no sound at all, period. What you are describing is 100% symptomatic of an open connection. While I'd like to parrot the "cold solder joint" party line, I've got another question for you.... Tell us, are you perhaps using the guitar's internal sheilding as part of the "ground" circuit?  sumgai |
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Post by yakkmeister on Mar 18, 2012 0:55:14 GMT -5
Um ... it's possible ... The pots and switch all sit on a metal bracket that is electrically connected to all the other 'earth' points. That meant, to me, that I already had the equivalent of earth connections between all the parts. The bridge 'ground' and the pickup 'shield' wires are connected to the backs of the tone pots and the jack's signal-return side is soldered to a common earth point... I think I may have bozo'd the grounding ... Edit: Picture of pots and switch in the metal 'thingy' in pre-nutz, terrible wiring mode Also shown - sneak peak of paint-job   |
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Post by reTrEaD on Mar 18, 2012 4:34:01 GMT -5
Ok, so I have done the test ... With my DMM in the 200k Ohm scale I got a reading of 37.2. That should mean 37.2k ohm, right? (it's been a while ... lol!) Yes. Seems a bit high for 2 s/c's ... Dano p/ups tend to go between 4 - 8k ohms DC... I would have expected max to be around 20, accounting for the extra wire? More than a bit high. Extremely high. Wire only accounts for an ohm or two. There is something VERY wrong. Turning the volume pots one at a time then both down to full-off, I have no change whatsoever in the reading, ditto with the tone pots. That was my next question .. were you turning the correct knobs? Dano uses the outer ring for the volume. But since you've turned both inner and outer with no change, that eliminates the possibility of turning the wrong knobs. Vintage Dano pickups were closer to 4k, but I'm not sure about the reissues. Anything substantially over 10k for the whole system raises a red flag. You're at 37k! Rotating the controls doesn't change the resistance. If the wipers weren't making contact to the resistive element, the only path would be through the 150k resistors for the treble bleed. in that case we'd expect to see about 300k, not 37k. I'm currently unable to imagine a disease that fits these symptoms. |
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Post by yakkmeister on Mar 18, 2012 5:11:44 GMT -5
I'm currently unable to imagine a disease that fits these symptoms. Indeed. The only resistances high enough for that are the 1M ohm tone pots. One of them reads open circuit and the other seems to me to be serviceable ... I will re-check and report. Edit: Volume pots are reading 150K ohm over the pins with the treble-bleed circuit over them while the other pins are totally different ... the Neck pot is changing resistance as expected but the neck pot reads totally open; same as the bridge tone pot. |
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Post by reTrEaD on Mar 18, 2012 10:00:57 GMT -5
the Neck pot is changing resistance as expected but the neck pot reads totally open; huh? |
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Post by yakkmeister on Mar 18, 2012 10:23:56 GMT -5
the Neck pot is changing resistance as expected but the neck pot reads totally open; huh? Er ... I mean bridge ... the bridge pot reads totally open ... Oops! |
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Post by sumgai on Mar 18, 2012 14:26:09 GMT -5
yakkmeister, As in days of yore (when ChrisK roamed these hallowed halls), I must restate that maxim (best practice), the one that says "shielding is not meant to carry any part of the signal, not at all!" IOW, if you depend on the shield's "electrical abilities" to carry the so-called ground portion of the signal, you are asking for Trouble with a capital T. My suggestion (albeit offered with knowledge that I've not seen your latest wiring iteration) is to use real wire between all points that are considered signal ground. You can leave the shield in place, and connect it to the output jack's ground lug, but you don't want any pickup signal (ground, negative, whatever) to be dependent on that shield material. While most shield materials have pretty low resistance, some materials are hard to connect electrically. We can't solder aluminum, nor paint, so we depend on physical connectivity through pressure - not the best idea, electrically speaking. This is why I espouse copper foil (tape works too), with or without adhesive on the back. Way too many studies have shown this to be the best all-around shielding material, both in terms of reducing noise and in ease of working/soldering, etc. Other things work, and possibly work well, but there will be some kind of compromise, you can count on it.  HTH sumgai (EDIT: made a minor grammatical correction, that's all.) |
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Post by yakkmeister on Mar 18, 2012 21:48:43 GMT -5
Duly noted...
And thanks!
I have ordered new pots and a new switch as well. I suspect with these in functional order plus the above advice, I should have a robust wiring scheme.
1 question about the treble-bleed portion ...
I have installed a 1nF cap (102J) and 150k ohm resistor in this circuit ...
Since the 150k Ohm resistor is all I am reading over the volume pot ... is this perhaps a potential source of the problem as well?
Should the resistor be much smaller?
The original pots are 1M/150K ohm stacked ... the new ones are listed as being 1M/100K ohm stacked (due to the physical requirements of the guitar, I have little choice in this selection).
Won't 150K ohm be too much? or will it be too much?
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Post by reTrEaD on Mar 19, 2012 7:01:47 GMT -5
I have ordered new pots and a new switch as well. I suspect with these in functional order plus the above advice, I should have a robust wiring scheme. Makes sense. At least one of the pots was bad and it sounded like your switch was beginning to fail mechanically. While you're waiting for parts, I'd suggest checking your pickups. Since there were readings that can't be explained, suspect everything. Measure the coil resistance and also measure resistance between one of the coil wires and the shield wire. 1 question about the treble-bleed portion ... I have installed a 1nF cap (102J) and 150k ohm resistor in this circuit ... Since the 150k Ohm resistor is all I am reading over the volume pot ... is this perhaps a potential source of the problem as well? No, the reading indicates no continuity between the wiper and the element. Should the resistor be much smaller? The original pots are 1M/150K ohm stacked ... the new ones are listed as being 1M/100K ohm stacked (due to the physical requirements of the guitar, I have little choice in this selection). Won't 150K ohm be too much? or will it be too much? I think the choice of resistor and cap are based the external (cable) capacitance. JohnH would be a better source of info on that. |
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Post by yakkmeister on Mar 19, 2012 7:48:23 GMT -5
I have ordered new pots and a new switch as well. I suspect with these in functional order plus the above advice, I should have a robust wiring scheme. Makes sense. At least one of the pots was bad and it sounded like your switch was beginning to fail mechanically. Yes, it was... these parts are pretty old and the guitar has been out-of-service for most of it's life, so I am not terribly surprised. While you're waiting for parts, I'd suggest checking your pickups. Since there were readings that can't be explained, suspect everything. Measure the coil resistance and also measure resistance between one of the coil wires and the shield wire. Is there a special set of tests I should do for this? If the pickups were borked, wouldn't they have no output? Should the resistor be much smaller? The original pots are 1M/150K ohm stacked ... the new ones are listed as being 1M/100K ohm stacked (due to the physical requirements of the guitar, I have little choice in this selection). Won't 150K ohm be too much? or will it be too much? I think the choice of resistor and cap are based the external (cable) capacitance. JohnH would be a better source of info on that. If the pot value makes no real difference to these values, I am happy to just stick with them ^_^ |
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Post by reTrEaD on Mar 19, 2012 8:06:16 GMT -5
If the pickups were borked, wouldn't they have no output? That depends on how borked they are. Is there a special set of tests I should do for this? Not all that special. Measure the resistance of the coils. Measure resistance between the shield and the coil. In addition to identifying a possible problem, knowing the DC resistance of the coils is important data if troubleshooting is necessary at a later time. |
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Post by yakkmeister on Mar 19, 2012 10:51:29 GMT -5
Results are in!
Pickups were removed for testing.
Both P/Ups measure almost identical DC resistance.
Neck: 3.79K
Bridge: 3.80K
There was no continuity between either signal leads and the shield.
I guess that rules out the pickups...
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Post by reTrEaD on Mar 19, 2012 18:34:28 GMT -5
k, koo
now just refine your drawing while waiting for the parts.
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Post by yakkmeister on Mar 19, 2012 23:28:22 GMT -5
k, koo now just refine your drawing while waiting for the parts. Yessir! Sounds like a plan... |
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Post by yakkmeister on Apr 8, 2012 22:13:51 GMT -5
Hey blokes! I picked up my parts last night and I realised I have yet to update this wiring diagram. So here it is - I figured I should be sure it's all correct before soldering everything together ...  |
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Post by newey on Apr 8, 2012 22:32:27 GMT -5
Yak-
Look at the bright red wire from the bridge pup (which is the signal "hot", or so we'll call it). Compare it to the red wire from the neck pickup. They both should be wired the same.
The Bridge pup (bright) red wire needs to connect to the tone pot, not to the volume pot.
Other than that, the rest looks OK to me.
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Post by sumgai on Apr 9, 2012 1:57:01 GMT -5
yakk,
Don't bother newey on weekends, he's tryin' to catch up on his 420 quota..... ;D
Your Bridge wiring is fine, it's your Neck that's gonna surprise you, big time. Move the red wire to the Vol pot, just as the Bridge is wired, and you should be good to go.
HTH
sumgai
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Post by yakkmeister on Apr 9, 2012 10:27:46 GMT -5
yakk, Don't bother newey on weekends, he's tryin' to catch up on his 420 quota..... ;D Your Bridge wiring is fine, it's your Neck that's gonna surprise you, big time. Move the red wire to the Vol pot, just as the Bridge is wired, and you should be good to go. HTH sumgai lol - Thanks! I see where I have it wrong. I was running late for work ... I'll fix it up when I get home (it's a sleepover shift) and post the correct version, just in case anyone else ever needs this ...  |
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Post by yakkmeister on Apr 10, 2012 5:34:23 GMT -5
So, a word of warning ...
The original pots in the U2-56 reissue has the 1M ohm pot ganged on top of the volume (like in my diagram) but the Allparts pots are the opposite way around ...
Time to completely re-do several hours of work ... FML.
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Post by yakkmeister on Apr 12, 2012 3:18:51 GMT -5
Ok, so this is all kinds of bullcrap.
I sorted the pots out, no problem and I wired it all up correctly (accounting for the error in my wiring diagram)...
Switching works like a charm - happy with that
The pots do nothing.
I checked the resistance on the guitar cord as before.
200K ohm range selected. Meter reads:
18.3 on bridge
16.3 on neck
34.5 on both
Again, I have stupidly high resistance and non-functional pots.
I have to get moving now, but I am going to rip out the treble-bleed circuit and see if that fixes it ...
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