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Post by bigdaddyweed on Apr 1, 2006 21:29:40 GMT -5
Hello, I am new to this forum, and a big thank you to the people who host this site.
I recently bought a 1994 LP Special with the intent of replacing the P100 pickups with P90's. I played the guitar and made sure everything was working correctly before taking it apart. Once I got the pot cover off, I found where someone had run ground wires from pot to pot, looked like a spider web. Anyway, I got rid of all those, and shielded the cavity, it has a little hum, but no interference noise. Now, here's the rub. The bridge pickup absolutely screams (what I had hoped for) but the volume pot for it turns it on and off, and the tone pot works fine. The neck pickup is dull and lifeless, the volume pot works okay, but the tone pot does nothing to the tone.
I switched the tone pots around, but got the same results. I switched the caps, and nothing changed. What have I done wrong? Please help!!!
I didn't think this would be a problem. I'm not a professional electronic wizard, but I've change pickups in LP's, Strats, and Tele's, and never had a problem.
I truly appreciate any input, thanks......Weedman
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Post by flateric on Apr 2, 2006 8:23:09 GMT -5
Can you post a schematic? Has the wiring been changed from a stock LP scheme?
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Post by sumgai on Apr 2, 2006 22:01:02 GMT -5
Daddy, Hi, and to these here forums! What you've described is a common ailment. There is a solution, if not an easy one. Since everything worked as it should before you started (good move, testing beforehand like that), then you can rely on the pickups being good. Don't take it to the bank, because something could gone wrong while you had it open, but that's not very likely. So, all you have to do is retrace the steps you took. Did you unsolder anything? Did you resolder everything back together, even if to some other physical location? Did you do this? Did you do that? You get the idea by now. Just go through the motions again, and it should become clear if you missed a step during the "put it back together" phase. A couple of other things. Did you solder cleanly? No cold joints, no blobs laying across two terminals that shouldn't be connected to each other, good tight, mechanically sound connections? If wires are 'just touching', and you're depending on solder to 'carry the day' (make a connection), then you're in for a rude awakening. Visual inspection is the order of the day, make it as close as you can. And finally, did you apply heat (the soldering iron tip) to any one component too long? You can melt a pot's internal connection, or even a switch contact point, if you apply too much heat (and it doesn't take too long to build up to the "too much" point, believe me). What about the pickup's wiring itself, did you booger that up without realizing it? Better go look, closely and carefully. Next step (you didn't think I was through, did you? ): You say that you switched the volume and tone pots around, with no luck. That is what I was gonna suggest next, but you beat me to it. So, assuming that you have an ohm meter of some kind, it's time to double-check, and make sure, that the pickup is (or is not) bad. Disconnect all the wires on that "bad" pickup from the rest of the controls and stuff, and do a resistance check across the coil. What'd the reading say? There, that should keep you busy, and off the streets, for a few hours. ;D Report back when you're done, successfully or not. sumgai p.s. FWIW, even after more than 4 decades of doing this for a living, I still make some of the above mistakes. No more than once or twice a year, to be sure, but that's why I test everything for at least half an hour before I return it to the customer!
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Post by UnklMickey on Apr 3, 2006 8:43:53 GMT -5
... The neck pickup is dull and lifeless, the volume pot works okay, but the tone pot does nothing to the tone.... i think that tells the story. high probability the tone cap is wired across the neck pup. look for shorted tone pot or wiring error to tone pot. unk
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Post by bigdaddyweed on Apr 3, 2006 13:57:37 GMT -5
Thanks you guys for quick replies. We had a tornado around here yesterday (central Illinois) and just got our power back.
The wiring schematic hasn't changed. I have already retraced my steps, I also learned that the hard way. I guess when I asked for help, I was thinking there was some instant solution to this problem, but I guess that was wishful thinking on my part.
The "good" connection part of this makes good sense, I sometimes rely on the solder to be this great electrical conducter. Also, I very well could have gotten one of the pots too hot, because some of these ground wires, there were so many, had about $5 worth of solder hoding them on. Tone cap wired across the neck pickup? Please explain that a little futher, I'm not sure what you mean, or is it so simple I'm looking past the obvious? Well, out comes the voltmeter, but first, another question. This guitar had set in its case for the last 6 years, according to the previous owner, would I be better off just ordering new pots and starting all over? The cost is not an issue, would good replacements be as good or better than the originals?
Thanks again....weedman
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Post by CheshireCat on Apr 3, 2006 14:51:49 GMT -5
... The neck pickup is dull and lifeless, the volume pot works okay, but the tone pot does nothing to the tone.... i think that tells the story. high probability the tone cap is wired across the neck pup. look for shorted tone pot or wiring error to tone pot. unk Also, with the bridge pickup, perhaps a linear taper vs. audio taper pot?
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Post by UnklMickey on Apr 3, 2006 15:46:04 GMT -5
...had about $5 worth of solder hoding them on. Tone cap wired across the neck pickup? Please explain that a little futher, I'm not sure what you mean, or is it so simple I'm looking past the obvious? Well, out comes the voltmeter... i think we may have the last piece of the puzzle. the stock wiring on a LP will have the pickup connected to EITHER the cw OR wiper (center) lug of the volume control. the treble-cut tone circuit is also connected to the same terminal. the tone circuit is just a capacitor in series with a pot. if one of those $5 solder blobs is bridging the terminals of the tone pot, the tone cap is effectively wired directly across the pickup. it would be as if the tone pot is permanently set at zero (maximum cut). and it won't matter where the pot is set. okay sound if you're going for a stereotypical jazz sound, but otherwise, not too versatile. i wouldn't bother with replacing the pots unless you are having noise (scratchy when turned) problems with them. the full sized Alpha brand are okay if you do need to replace the pots. aside from the resistance value and taper, make sure you get the right shaft/bushing length (most LPs require a longer bushing because they go through wood) and a split-shaft (so you can use your push-on knobs) unk
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Post by bigdaddyweed on Apr 6, 2006 22:24:24 GMT -5
Thanks, Unk, and everyone else. I've had so much jamming and practicing going on, I haven't had time to trouble shoot this problem any more. Also, this stupid day job keeps taking up all my time. Anyway, I'm gonna try and work on it some more tomorrow afternoon. weedman
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Post by sumgai on Apr 6, 2006 23:27:46 GMT -5
Daddy, The heat I referred to was when you solder a wire (or two or three....) onto one of the three terminals. The heat can/does travel down the line and into the joint where the terminal connects to the resistance element. However, the casing itself does not contact any of the internal workings, so it should withstand quite a bit of heat without any causing any problems.
I wouldn't replace the pots summarily, I'd test them first. And by that, I mean a field test, playing in the wild, at a gig or a jam, whatever. It'd be a shame to spend money, time and effort needlessly.
That is, unless you've got some other reason to actually change the control's values, and perhaps the caps, too. In that case, d4mn the torpedoes, full speed ahead!
sumgai
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