Repair And Restoration
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Very strange pickups problem
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Very strange pickups problem
I’ll start by saying I don’t post much because it’s confusing to know if I should post on this site or the Patreon site, both are hard to navigate, etc. Also, I sent this question to the last “elder” meeting but I have no idea what the outcome was (I thought there would be some answers documented for those that can’t attend live). So, with those frustrations out of the way…
I have in my backlog a 1988 PRS Studio. It has HSS pickup config with master vol, master tone, and the first gen 5-way rotary (the stacked version, not the PCB version). All components are original and the wiring/solder points appears unaltered.
When the humbucker is active, the tone is really nice and the vol/tone controls work as expected. When either of the two single coils are active (alone or together), they sound out of phase, very hollow and lacking low mids/bass frequencies. Here’s the kicker – the volume works as expected but only cuts about 85% of the volume at full off position, while the tone control acts like a volume control and cuts about 70% of the volume at full off. The tone control has zero effect on high frequencies, only output (volume). When both vol and tone are at full off, the output is cut completely.
By the way, all three pickups are grounded to the same place along with the pots, switch and bridge.
I really want to preserve the original wiring as much as possible, this being in the “vintage” years of PRS. I’m thinking there could be a cut in the coil windings on the single coil pickups. Just to note, these singles did not come with a plastic cover, they are wound, wrapped in tape, and installed… and I can see exposed coils where the tape has worn (come on Paul, you should know better). To have both singles go bad at the same time is something I haven’t experienced, and that doesn’t explain the tone control acting like a volume control….
I’m stumped.
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6 Replies
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I’m glad you posted this again. We did talk about your question during the council, but it’s going to take a bit before the video is processed. Also, this post has much more information. I’ll get this before Gerry now.
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Also, would it be possible to post a pic of the cavity ?
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Here you go. With the grey pickup leads out of the way, you can see the white ground wires from the volume pot, tone pot, 5-way, and bridge all soldered together with the mass of plain wire from the pickups (as PRS used to do). None of these are touching the shielding in the cavity. There’s a capacitor running from the volume pot to the tone pot but it’s not touching the shielding either.
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I haven’t yet pulled the rotary switch, I’m not looking forward to this:
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Hey Jason
There seems to be a lot going on all at once. I talked about first impressions on the council of elders discussion but David Collins had a great idea.
My first thought on the tone control acting like a volume was to consider the tone capacitor. When caps break down, sometimes they can start to pass all frequencies rather than just the higher ones. When it’s working, you can think of a tone control as a volume for highs and, if the capacitor breaks down like this, it can be a volume for a wider range of frequencies.
David was sharp enough to recognise that your weird single coil tones could be related to the coils degrading. The insulation on the coil wires can break down and do very weird things. These can often sound like low-output, out of phase tones. I’d originally disregarded this possibility because you mentioned that you’d been able to measure a DC resistance of 5.something on the singles and that wouldn’t normally jibe with this problem. But, if you’d measured the pickups without disconnecting them from the rest of the circuit, you could have gotten erroneous readings. So, it’s worth un-soldering all the pickups and checking their resistance again.
This is definitely a good track to pursue since you mentioned some worn tape and exposed coils. Also check for any corrosion around the coils or poles. That can be an indicator too.
Since we’re on the subject of unsoldering, I don’t think you’re getting out of this job with original solder joints intact. 😄 Start by taking the pickups out of circuit and re-test them. If you had a couple of spare singles around, it’d the a great idea to try them in circuit to see if they work. The more I think about this, the more I think David was on the right track and you’ve got some failing singles.
Of course, troubleshooting wiring remotely isn’t straightforward so update here when you know more and we’ll keep working if needed.
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Thanks Gerry! I know how it is trying to troubleshoot a guitar without having it in your hands, so I appreciate the effort. I’ll start with the singles and see where it goes from there. Many beers will be consumed before this is over, I suspect.
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