APX-10A - System 29 Preamp Issues

APX series guitars are designed with a focus on playability. Their thin bodies and cutaways that provide greater access to the upper frets, offer smoother switching between electric and acoustic instruments.

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Island Mojo United States of America
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APX-10A - System 29 Preamp Issues

Unread post by Island Mojo »

I'm on the global search for info on locating an original replacement preamp (used of course) for an APX-10A. It came with the System 29 preamp. This same preamp was also installed on these APX guitar models: 8A, 8CS, 10C, 10CS, 10CT, & 10NA.

The problem I'm having is that the output on the 3 lower strings is considerably and noticeably lower than the output on the 3 higher strings. Sadly, and to no one's fault but my own, the guitar was stored in a non-humidity controlled environment for a few years, and I suspect some circuitry corrosion has taken place. So ultimately I'm looking for a replacement, but any ideas and/or suggestions will be appreciated.
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TheSupposedStringMeister New Zealand
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Re: APX-10A - System 29 Preamp Issues

Unread post by TheSupposedStringMeister »

Island Mojo wrote: Tue Jul 09, 2024 3:15 pm I'm on the global search for info on locating an original replacement preamp (used of course) for an APX-10A. It came with the System 29 preamp. This same preamp was also installed on these APX guitar models: 8A, 8CS, 10C, 10CS, 10CT, & 10NA.

The problem I'm having is that the output on the 3 lower strings is considerably and noticeably lower than the output on the 3 higher strings. Sadly, and to no one's fault but my own, the guitar was stored in a non-humidity controlled environment for a few years, and I suspect some circuitry corrosion has taken place. So ultimately I'm looking for a replacement, but any ideas and/or suggestions will be appreciated.
I have the APX-10 which comes with a totally different pre-amp. However, I don't believe that the the guitar living in a non humidity controlled environment will affect only part of the pre-amp circuit. All my guitars live in a room without humidity control and no issues.

I note your photo has the EQ bass set to nearly -12dB so that would remove most of the lows. Anyway, I would put a new battery in, set all control to their middle position, equalisers at 0 and try it again. If it doesn't change then perhaps your LOW volume slider might need some contact cleaner spray applied.

Attached the document which has some good info on the system 29, including the circuit diagram.
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Saul Ukraine
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Re: APX-10A - System 29 Preamp Issues

Unread post by Saul »

It is always possible of course, that you have some sort of corrosion/oxidisation of the electronics. Have you checked the capacitors? They can leak and/or dry out over time.

The first thing I would do though, and you may have already done this, is remove the saddle and check the pickup for any damage. Also, make sure the saddle is sitting perfectly flat against the pickup.

Check the connector from the pickup to the preamp. Unplug it and look for corrosion, maybe spray some switch cleaner in there and plug it in and out a few times.
Saul
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