Electrocompaniet AW-100 troubleshooting (right channel intermittent soft popping)

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My Electrocompaniet AW-100 has developed a soft intermittent popping noise on the right channel. The only way I can reliably cause those sounds to occur is when I turn it on after it's been off for a long time. The popping noise is extremely intermittent and random in frequency. It can be hours without hearing any noise or quiet pops and then suddenly, 2 mins of popping. It seems to occur irrespective of whether any music is actually playing.

Unfortunately I don't have the schematic because Electrocompaniet made numerous different versions of this amp over the decades. In their infinite wisdom, they chose to write the serial numbers on the world's cheapest paper stickers and this amp is over 25 years old so all of the stickers have lost their sticking power and without a S/N, Electrocompaniet can't help me.

I was told by a repair guy in NC that it's probably a problem in the output stage and I'm willing to restuff the boards (which should be interesting without a schematic, and matching transistors isn't fun. There's also a few components that look like resistors but I'd have to double check with you guys if they in fact are. There's a silver one labelled 1000 H and a pair labelled 220 H).

Any suggestions for what I should try/check first?

With my limited knowledge of electronics, I thought it would be a good idea to try replacing the caps in the output stage.

I've tried to use that Aerosol freezing spray on individual components to see if the popping would reoccur and that did not work unfortunately.

Any help is greatly appreciated!
I'd be sad if this was the end of line for my EC :(


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EW likes to toast semis since working them hard measure and sound better. DONT look in the output stage ..this is wrong, pops like that is typical failure of the front stages NOT the output ...Messing things up there might cause more trouble than you ever thought

You need to inspect the board for dry joints but i think that your problem lays elsewhere

Your only friend in this is heat and freeze

You will need to freeze small semis one at a time to see changes in behavior Heat might do the same trick with a focused heat gun but in your case freeze i think will produce a better result .Start from the input and advance up to the drivers ...

Don't make explain why ...it too long to write ...

If you manage i will let you know about factory bias and even if you had a schematic you may learn a few things about how the amplifier work but it will not help you to troubleshoot the amp so i don't see any use on giving it to you ....:D:D:D

you may use a small speaker in the output if you don't have instruments to be able to hear what is going on But remember to put in series a considerably large capacitor that will work as a DC blocker Freezing semis can and will produce some amount of DC in the output
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I would do a visual inspection for dry joints first.


I've looked for dry joints before and hadn't found any. There are/were no obvious dry joints but I figured I'd reflow all the joints before trying to restuff the board anyways because the A1038 transistor is no longer available.
I didn't believe it but that seems to have done the job!

The amp has been left on for the last 24 hours and I have yet to hear any crackling sounds. I'd forgotten what a spaceheater this amp was but it's working again which is fantastic. A big thank you to all of you who chimed in!
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