Amp Forum - FM Labs 800A repair

FM Labs 800A repair

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Category: General
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=109356
Printed Date: 27 March 2026 at 7:15am
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Topic: FM Labs 800A repair

Posted By: Bololoco
Subject: FM Labs 800A repair
Date Posted: 14 December 2025 at 9:37am

Has anyone ever worked on this amp? I have one that blew on me.

I brought it inside from the garage where it had been stored in a flight case, rested it for a few day with a dehumidifier, turned it on and fizz.

I understand that I can buy spares, I just want to know whether they're easy to work on?

Replies:

Posted By: Bololoco
Date Posted: 18 December 2025 at 12:49pm

Anything anyone?

Posted By: madboffin
Date Posted: 18 December 2025 at 5:40pm

A assume you mean FM Acoustics, not FM Labs.

I don't know anything about those amplifiers, except that they were designed for studio monitoring in the 1970's and, at the time, very highly regarded in that market. The company was based in Switzerland and they were very expensive, which is probably why they were a rarity.

First thing to check with an amplifier of that age (and the most likely point of failure) is electrolytic capacitors.

Posted By: jblfreak
Date Posted: 21 December 2025 at 3:40pm

These amps, no idea why, still go for stupid money like 3 grand. I'd bring it to the best repair shop you can find locally and don't risk it fiddling with it yourself (unless you're a tech yourself ;) ).

Posted By: Bololoco
Date Posted: 24 December 2025 at 10:14pm

I got it slightly wrong....it's actually FM 800A Laboratory Amplifier but it's not FM Acoustics, at least that's not written on the chassis.

Yes, I understand they're highly collectible and as far as I know this one has pedigree, although it was originally half of a pair. I bought one with the knowledge that the other was going to be saved for me but he let it go to someone else.....my loss!

I've been told that it's worth 3k as it is (not working) and up to 7k working....perhaps even more if I can provide proof of its history, which is possible if I can find a database of serial numbers.

I suppose I can ask for help from the person who sold it me as he's been in the audio design business for 50 years or thereabouts. I would send it to him but he's 300 miles away and the thing weighs a lot, hence me maybe having a go at it.

I'm alright with a soldering iron and to my knowledge, it only needs a few components replacing, rather than a deep knowledge of amplifiers, although tracing the exact components may be a challenge but as you say, electolytic capacitors would be a good start.

Many thanks for the replies guys...it may not seem like it but you've actually helped a lot with my decision making.