• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Yamaha m4 needs some help

B

Bootcoot

New Member
Hey all, first post here.

I recently picked up a Yamaha M4 amp on Facebook. When we tested it it sounded good (BA A200 speakers) but had dirty pots. I have since cleaned the pots with deoxit and they turn smoothly. When I plugged everything in the right channel (speaker A) would go in and out and also sound scratchy at times (no knobs turned). After a while I decided to try speaker B to see if I had any luck. To my surprise it worked just fine, but after a few hours I would get the same issue. Now the relay doesn’t click when I enable speaker B, but still does on A. Speaker A still has the same aforementioned issues with the right channel. I checked the relays and they were clean, however, I destroyed one in the process (loosened the spring). I do have a digital multimeter and soldering iron so was wondering where to start with troubleshooting. Thanks, Bootcoot.
 
Register to hide this ad
Clean the speaker selector switches as well . And replace both relays regardless .

Then report back . I guess you can use the one speaker out with the good relay to see if the switch cleaning worked.

Athanasios
 
Nashou66 said:
Clean the speaker selector switches as well . And replace both relays regardless .

Then report back . I guess you can use the one speaker out with the good relay to see if the switch cleaning worked.

Athanasios
Click to expand...
Forgot to mention I cleaned the speaker selector switches as well. Its currently disassembled on the dining room counter (the WAF rating is through the floor). Where would one go for new relays, ebay?
 
Have to solder the relay back on. I’ll message again when it’s done and I’ve listed to speaker B. Wouldn’t happen to know where to get binding posts and LEDs would you?
 
avionic said:
Lots of options. Depending on your mechanical abilities.
Click to expand...
I’ve got a screwdriver and scissors.

I tried my hand at soldering the relay. My tip wasn’t heating up the solder so I thought I’d press a little harder, slipped and scratched the board (is it bad?). Switched tips and soldered fine. I’m gonna plug everything back and test speaker B. See you in a sec.
image.jpg
 
Bootcoot said:
Never mind. Do I need a new power board?
Click to expand...
No looks fine , just clean it with Denatured alcohol or acetone. I always clean board before I begin repairs so I can look at a nice clean board to find any bad solder connections and cold joints .
 
Update: relays came. Installed them. Speaker B relay does click still. Might be something with the switch. Speaker A works reliably but the right channel doesn’t sound as good as the left channel. What’s with the plus/minus 65V and DC balance dials?
 
Bootcoot said:
What’s with the plus/minus 65V and DC balance dials?
Click to expand...

Yamaha M-4 DC Offset

Picked up a M-4 power amp. Appears to be clean and fully operational, the input level pots will need a shot of Deoxit but that is about it, I think. The DC offset is 35mv and 77mv, not terrible from what I have read, but could be better. I see a couple of pots marked "DC Balance" that are just...
audiokarma.org
 
You must log in or register to reply here.
Back
Top Bottom