Adcom GFA-565 Replacement Circuit Board


SKU: adcom-gfa-565-replacement-circuit-board Categories: , ,


Replacement circuit board for Adcom GFA-565. (Original model)

Blank circuit board. I do not sell assembled boards, sorry.

This is the cure for leaky capacitors and DC offset problems in the original Adcom GFA-565. Unfortunately, nearly every GFA-565 ever made was affected by a bad batch of leaky Elna capacitors. (A good brand, but a defective batch.) The DC offset issue often persists, no matter how well you clean the board. The electrolyte actually soaks into the fiberglass, making it ever-so-slightly conductive, and affects the high-impedance circuitry around the input stage. My solution is a new board!

Read more about it here.
How to Fix Leaking Capacitors in the Adcom GFA-565 for good!

Skills Required:

This is a job for an experienced amplifier tech. If you have not fixed amplifiers before, the GFA-565 is not a good place to start. It is a fairly complicated beast, and assembling the input board is quite a meticulous undertaking—though very satisfying once complete. Given the complexity of the design, and relatively high component count, it is very easy to make a small mistake in assembly. Mistakes are perfectly normal, but you should be experienced enough to troubleshoot any issues that arise.

I can only provide limited tech support—answering questions about what parts go where, clarification on documentation, and such. But if would like help in troubleshooting your amplifier, by email, text, or phone, that service is available for my usual hourly rate of $60/hr.

Parts are all available from Mouser, Digikey and other suppliers. (No affiliation), and if you buy everything on this parts list, it’s around $110. That’s absolutely everything you’ll need, not just for the input board, but for a thorough refurbishing of the whole amplifier, including higher-voltage driver transistors, parts for the soft-start board, power switch, etc. Likely, you can re-use many original parts to save money.

I also sell matched sets of input transistors, along with their cascodes, 8 matched transistors in total for $50. Matching these devices is kind of a big deal, and a whole project in itself. Some people don’t want to go through that hassle, so I sell matched sets. I’ve built a test jig to sort and match transistors, based on this discussion at You can use the original transistors if they are good, but they often have electrolyte goo on their leads, so if you do re-use the originals, make sure you clean them really, really well, and that the leads are not corroded too much.

Before ordering, please read through these instructions to be sure this is a project you’re comfortable doing.

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