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My Yamaha APX 8D's preamplifier is broken.
Does anyone know a good replacement?

The guitar has a piezo pickup and a microphone.
There are potentiometers for volume, treble, bass and a 9V battery compartment.
I would like to keep the pickups in place and simply use a replacement preamplifier.It would be great if I could leave the potentiometers as they are.
I asked several workshops, but they always wanted to replace everything.
I don't have a soldering station at the moment, but I know how to do it.

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    "I asked several workshops, but they always wanted to replace everything." Of course they do. It's quicker, cheaper, more reliable, and easier to give you a guarantee that the complete package works and will stay working for years. If you really want to a "pick and mix" solution, either learn to do it yourself, or find a specialist - and if they are any good, you will be paying "specialist" prices. (If they are cheaper than a "workshop" quote, then run away before you discover you have thrown your money down the drain...)
    – user19146
    Sep 1, 2017 at 14:42
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    I don't really care about the pickups. The guitar has this mini-invasive thing which can be seen here goo.gl/images/UwWbGy and another poti close to the neck. The battery comportmant is a bit further down on the body. So replacing the preamp with a fishman e.g. would create another hole to the body. Maybe I should just find somone who can resolder the caps or just get a pickup wired to the plug and use an external preamp
    – macbert
    Sep 4, 2017 at 10:56
  • I think there may be an issue here in that the existing pots etc. may not be perfectly compatible with the circuit designed for the new system. They might be, they might not be. If you can determine the specs of all the components, and decide they are compatible, you might be able to e.g. cut some wires and splice the old parts in.
    – Yorik
    Sep 5, 2017 at 14:51

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You will have to do some research. You will need to find out the part number for the pre-amp in the assembly. It is possible the pick up system is in the service manual for the instrument, but likely not, as manufacturers will change what system they are using on a model and often don't include them in the manual.

I would start by calling Yamaha and seeing if you can get the part numbers directly from them: (888) 892-6242

You can order the service manual from Yamaha here: https://usa.yamaha.com/support/parts_manuals/index.html, and parts at https://www.yamaha24x7.com, although it requires web site registration (just an e-mail address really)

I checked the parts site for your guitar model since I have a log in, and didn't see the pick-up listed, just the regular guitar body parts (tuners etc.)

You may have to call Yamaha and find out what manufacturer made the pickup system and get the part numbers and possibly replacement part directly from the pick-up manufacturer.

In some cases when a guitar model hasn't been made for a few years it is impossible to find a direct replacement. I have been able to replace pre-amp boards with non-stock boards with some clever rebuilding, but that may not be a project you want to undertake.

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  • Okay, I've also checked the customer's website and it looks like they're only supplying mechanical parts, but not replacements for preamplifiers and pickups. That is a really sad policy. I guess it will be cheaper to get a good replacement guitar instead of repairing the Yamaha. So I should get rid of these sentimental feelings about the first E-acoustics, which I bought at the age of 18, for about $600 USD - that was a lot of money for me when I was just starting at university. Maybe I'll try to fix it myself by re-soldering the capacitors - if I have time in my late sixties. :-)
    – macbert
    Sep 13, 2017 at 8:29
  • I couldn't find the details on the pickup(s) that model has, but it would likely be worth your time to bypass the built in pre-amp system all together. Assuming it has a piezo under-saddle pickup, you could connect that to something like an end pin pre-amp unit with minimal time and effort, giving you amplification again. It wouldn't have the same sound as the original pre-amp, but would bring the guitar back into use. The end pin pre-amps range in price and quality, starting at about 10USD, up to hundreds for Brand Name versions.
    – Alphonso Balvenie
    Sep 13, 2017 at 19:28
  • Finally I got it fixed by letting add a replacement preamp from fishman inside sound hole and reusing the battery box. The old control knobs are still there, out of order, but at least there is no new hole in the body now.
    – macbert
    Dec 20, 2018 at 16:39
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For the give price range I would typically suggest something like:

  • universal audio 710 twin-finity (costs around 700 dollars)

watch a demo of it here:

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  • Neat tool - I shure will get that :-)
    – macbert
    Sep 13, 2017 at 8:12

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