Noise in RM22. Help!

[mfgobbi]

I just got a RM22 and when I turn it on it makes this noise. Video below. After a few seconds the amp operates without that noise. I have switched all preamp and power tubes and modules, and the noise remains. Can anyone help where to look? Bad cap perhaps? Grounding problem?

I appreciate any help.

http://youtu.be/Mmk89mNBTAA

 

[Jaded Faith]

Unfortunately there is no schematic for the power amp on that unit. Here is what I can tell you from experience:

1: That type of in-rush noise is most often related to bad filter caps or tubes.
2: It could be a solder joint IF the problem reoccurs during use. If it's just during firing it up/down I'd look to #1.

Probably unrelated, but worth noting is that you need to screw in your modules thumbscrews to properly ground the preamps. Hope something here helps.

Rob

 

[mfgobbi]

Thanks Rob. If I tell you that it has no relation to bad tubes, that it happens regardless of module settings, and that the amp is lacking low end, although it operates without that noise, would you have any further tip where to look?

Unfortunately there is no schematic for the power amp on that unit. Here is what I can tell you from experience:

1: That type of in-rush noise is most often related to bad filter caps or tubes.
2: It could be a solder joint IF the problem reoccurs during use. If it's just during firing it up/down I'd look to #1.

Probably unrelated, but worth noting is that you need to screw in your modules thumbscrews to properly ground the preamps. Hope something here helps.

Rob

 

[Jaded Faith]

I wish I could offer more help remotely, but these issues are typically something I need a scope and the amp on the bench for. Probably related to caps, voltage regulators or a transformer.

 

[tschrama]

I just got a RM22 and when I turn it on it makes this noise. Video below. After a few seconds the amp operates without that noise. I have switched all preamp and power tubes and modules, and the noise remains. Can anyone help where to look? Bad cap perhaps? Grounding problem?

I appreciate any help.

http://youtu.be/Mmk89mNBTAA

I am thinking bias cap leakage, of tube going bad....

Pull the preamp tubes, one by one, powering up the amp after each removal. did one of the preamp tubes cause the noise? Is there still startup noise after all the preamp tubes are removed?

Has the amp fixed bias? Then you pull one of the power tubes and check for startup noise. Put it back and pull the other and check for startup noise.

Report back with you findings.