Yamaha B212 somtimes without sound

[Hannesder3te]

Hello,

I have a Yamaha 100 B 212. Since I have it (2 years) I happen to rund in a strange problem, two times.

I turn it on an it stays silent. If I krank it up to 10 I swear a little bit. The low tones are very distorted.
And then after a couple of minutes, it is back to normal. (You can imagine, 100 watt amp full cranked up in your face in the middle of the night...)

Do you have any idea what I can test to find out the problem?

Thanx in advance. Michael

[Enzo]

When it does this, ball up your fist and whack the top of the amp hard.  Does the amp react?  Does sound return, even for a moment?  That exposes loose connections.

If this is the amp I think it is, there is a large heat sink module for the power amp.  It plugs into the power amp board with a five or six pin connector.  I find the solder on those connector pins cracks sometimes.

Also do not overlook the common things, like FX return jacks or power amp in jacks.

[Hannesder3te]

Hello Enzo,

I think you are correct with the amp. It has a big heatsink module that connects with a 6 pin connector. I will have a look at the solder connections in that area.
Thanx for the hint.

The jags were the first thing I checked. After beating on it, I mean...  8|

Thanx, best regards
Michael