Adcom GFA-545 noise

[dapolk]

Hi,

I have an Adcom GFA-545 that occasionally makes a lot of fairly loud noise in one channel - here's a link to a video:

https://vimeo.com/user100134985/review/446289129/b149f68b25

The noise is only ever in the one channel. I've changed cables, playback sources, power sources, and it has persisted.

This noise will go on for up to hours, and it will eventually stop, and then the amp seems to operate perfectly, w/ great S/N ratio. When the noise isn't present it sounds great, and I've never heard any audio discrepancy b/w the two channels, imaging seems perfect, etc.
Then a few days later the noise starts back up again - probably about once a week or so on average. It's unpredictable when it's going to do that - sometimes it's immediately on power up, sometimes it's been on and silent all day, and then suddenly it rushes in. I haven't found any repeatable way of getting it to return to normal functioning, but it always does at some point.

I don't know much about power amps, so first of all was wondering if this sounded like an obvious known issue, like a bad PS cap or something?

Any help appreciated!

 

[moamps]

Your link doesn't work for me.

 

[peterc]

https://vimeo.com/446289129

Could be number of things, a dry solder joint, a failing component or a loose connection.

A good place to start is to get the service manual from here:
https://elektrotanya.com/showresult?what=Adcom+GFA-545&kategoria=All&kat2=All

Open te amp up and when it happens, take a chopstick and press down on the PCB in various places and see if it stops. Look around that area for dry joints or a burnt component.
Take a magnifying glass and inspect the solder joints for crystalisation and cracks.
Measure the DC voltages on both the channels and see if they vary from channel to channel.

Peter

 

[dapolk]

Will do, thanks!

 

[dapolk]

For testing the DC voltages, do you mean as in where you would test to adjust the bias for each channel? Or somewhere different?