Yamaha M-4, help needed with a problem

252525

New Member
Hi, first time poster here.

I bought a M-4 amp recently from ebay. After hooking it up I noticed that the left channel of the speaker pair A had some problems.
Sometimes when the volume is low from the preamp (Yamaha C-6) the left speaker goes silent, with just the highest transients/dynamics going through (with some light distortion/buzz). It's acting like a gate effect in a way.
If I turn up the volume the problem goes away.

The speaker pair B doesn't show any symptoms at the same time as this problem occurs on pair A. I've tried several different setups to pinpoint the problem and rule out any other source for it.

First thing I did before even hooking it up was to open the amp and have a quick look inside for bad caps, didn't see any. I haven't opened it since, thought I'd ask for advice here first.

What do you think the problem is? Bad solder connection, bad caps or something else? Where should I look first? I know there is some great knowledge amongst you for this amp!
I've got the service manual, if you need to point to a specific part.

The tools I've got is a soldering iron and a cheap DMM. I've done some replacing of bad caps on PC motherboards in my days, but what goes on in an amp is way over my comprehension.


On another note, I live in Sweden and we have 230V in our outlets. This M-4 amp is the general version with the 110/120/220/240 voltage selector. Should I run it in 220V or 240V? A simple explanation in layman's terms why one over the other is preferred would be interesting.
 
Hello !

Welcome on AK 252525 !

What do you think the problem is? Bad solder connection, bad caps or something else?

Speaker relays ! don't touch anything else !

Come back and give us the result of your investigations :scratch2:
 
Thanks for the reply and the welcome.
Do you know if the relays are easy/possible to open for cleaning? If not, any other way to check if they are the culprit?
 
Hello !

Cleaning relays is never as good as replacement by a new one .

As you know , time make things older and trying to keep a cleaned speaker relay is not fine

Yes you can easely test them with low level at the output of the M4 and knocking the relay cover with a screw driver handle and listen if one channel is disapear or not !
But level should be very low for this test
 

Attachments

  • M-4-relay.jpg
    M-4-relay.jpg
    126.6 KB · Views: 29
Back
Top Bottom