Losing gain on a LP bridge pickup

[weldaar]

EDIT: moved from Luthier to Wiring


I am working on this LP it is a 2003 LP Classic with 500T & 496R pickups. Ceramic caps. The guy tells me that he loses gain at some point. I never experienced this before so I went through the guitar, switch, pots. Wiring all seems good, no bad solder joints. Just for kicks I swapped the bridge pickup with a different 500T and upgraded the brdge pot with a CTS long shaft 300K. Played fine here. The next day he tells me, it happened again. I am at a loss. Could it be the tone pot or that ceramic cap? Thank you for your help with this.

[Deleted]

bad cable?
does it do it only on bridge position ?
can you make him reproduce the problem at your presence? or provide exact instructions to reproduce the problem?

[weldaar]

I asked him that and he never responded. Both pickups worked fine at my house through my rig. I have to ask him again if it happened with both pups. Played the guitar for over half an hour and nothing.

[newey]

I'm not familiar with these pickups, I am assuming they're passives. If they're active (or if the guitar has any active circuitry), then it could be any number of things . . .

The statement that the owner/operator:

loses gain at some point.

Suggests that he has gain when he begins playing it, but that the level drops off after some period of time.

If that is an accurate description, it sounds more like an amp problem. It particularly sounds like some component is overheating over time, and then causes the problem.

If so, that would explain why you weren't able to reproduce the problem through a different rig.

So, has the guy tried it through different amps? Has he tried other guitars through his amp?

[Deleted]

Hi Newey, those are Gibson pups, they are relatively hot, (suitable for rock, heavy rock) and assume they are passive, AFAIK (since i dont know of any Gibson actives).

[ux4484]

I'm with newey... Amp problem.

[bluemurder]

I agree. Sounds like an oscillation that breaks in at some point.

[weldaar]

Used a different amp, straight in. Tried different cables as well. I asked him to disconnect the cap from the bridge circuit, that should eliminate a bad cap or tone pot, right? If that doesn't work, I will change the switch although it seems OK. I already tried a different pickup, different volume pot. Unfortunately he likes those 500T ceramic pickups. I guess that they are good for heavier stuff. Thanx for all of your input.

Jeff

[sumgai]

Jeff,

In my 55+ years of messing around with guitars and associated equipment, I've seen plenty of guitars with flaky connections that cause the volume to cut in-and-out or up-and-down. But sadly (for me), I've never seen a passive guitar "lose volume"*, whereupon it stays lost until the next time it's picked up (presumably after a rest). Experience indicates to me that the guitar isn't at fault here, but then again, I can still be surprised at what Mr. Murphy comes up with, especially when he's having a good day.

I think the problem lays elsewhere in the signal chain. I suggest one of the following:

1) Have your customer bring over everything, and I don't mean leave the pedals or anything else at home. Test thoroughly.

or

2) Go to your customer's home (or gig setting, etc.) and observe for yourself just where the problem truly lays. You should have a second guitar on hand for immediate comparison testing, as a control. One of yours or another of his, makes no difference at this juncture.

I'll presume that the above can be accomplished, and that you'll report back with your findings. We'll get into more detailed troubleshooting at that time. But just for the nonce, if it turns out to be the guitar, then someone had best be re-heating every solder joint therein, regardless if it's factory-fresh or has been touched by a modder/repairman.

HTH





sumgai

* Guitars don't have gain, they have only Volume. The term "losing gain" is misleading, as it makes me think that the user is turning up the gain on a pedal or the amp, and getting little or no further increase in overall volume. That's a separate issue, and I hope you can either confirm or eliminate that possibility as his underlying problem.

[weldaar]

I hear ya about the gain term. Let me rephrase that. Loses bite, not volume. I tried all of the above mentioned. This guy and he is a friend, on his own, swapped the cap and tone pot. I would like to do a complete re-wire, this way I know that all of the joints are good. I will post my findings here. Thank you again for your input and patience with me
BTW, the loss of bite comes and goes. It doesn't stay gone until next time. Just some FYI Maybe switch?

[weldaar]

@ Newey >

So, has the guy tried it through different amps? Has he tried other guitars through his amp?

Yes, it's only with the said guitar no matter which amp, or cable.

[Deleted]

Does the guitar have push/pull pots?

[sumgai]

Jeff,

I'm getting a tad tired of moderating your postings so that they don't scream and shout at one's eyeballs. Please, for the luvva Gawd, stop using bold, font size 4 and whatever else you're doing - the defaults are fine. Thanks.




sumgai
Chief Cook and Bottlewasher

[sumgai]

Jeff,

So, the problems are sporadic and random, eh? Well, that's easier to track down.

Unless the switch has been abused over time (I think you said it was new, or nearly so), then I'd go after one of the pots next. Was it/were they tested before installation? How about the output jack, is it in good shape? Mounted securely and all that jizz-jazz? The cable/wires running out to it haven't gone gefooey, right?

And finally, for all the vast number of pickups made and sold every day of the year, there will be some failures - either total or partial. But this is the most expensive component, and the comparatively most difficult to R&R (exchange, as in Remove and Replace), so that should be the last thing to double-check.... unless you can see an obvious problem with a simple visual inspection.

Bite is also subject to interpretation, but I don't think it needs "discussion", I'm pretty sure I know what you mean. And I would put it down to a loss of output from the axe, but I'm wondering if your friend/customer ever plays cleanly, sans any effects. Under this condition, any dropouts should also be obvious, or so I tend to think.

On another plane of thought..... if this happens during different songs/tunes, could it be due to the player's method of picking? IOW, is he laying back, then "digging in", as the situation requires? If the pickups are truly sensitive to such differences, then it should be easy to try lowering them away from the strings, and see what happens. Just a thought.

HTH





sumgai

[newey]

OK, so if it's not the amp, and not the pickup (since you swapped it and he said the problem remained, although you apparently didn't reproduce it), we're pretty much left with pots, switches and wires. And, as sg noted, intermittent "on again-off again" faults are pretty common, but an intermittent loss of "bite" is pretty much uncharted territory.

There are a number of questions that haven't been answered. As gd asked, what about P/Ps? More basically, what is the wiring of this, in terms of switching, pots, etc? Are coils being split? (I'm assuming stock LP wiring here, but let's be clear).

Also, have you heard/experienced this fault, or just heard your friend describe it?

Does it occur on just the bridge pup, or the neck (or the combo N+B)also?

I'm sure someone else is tracking my thought here, but the only scenario I can come up with whereby a pickup could be "on" but intermittently lose "bite" would be if there was a faulty "series junction" connection between the two coils of the HB, such that it would be intermittently grounded to the pickup frame. This could cause an intermittent coil cut to a single coil, which might indeed seem to represent a loss of "bite" (and some output as well).

Coil cut switching could make this a more likely scenario, that's why I asked about that. If it's not, then it's harder to see how such a fault could happen on two different pickups.