Yamaha M-4 in & out of protection - HELP?

bobrown14

bobrown14

Super Member
My Yamaha M-4 is going in and out of protection - click click click no music. Last night I bumped the pre in cable while the amp was on and got a loud HUM (not affected by volume either) - powered off right away, then hooked the cable back up properly and it started the clicking protection thing.

Any suggestions on where to look for a fix??

Thanks,

Bob
 
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You have a problem with your preamp ie solder connections on the RCA jacks,or possibly you have a bad interconnect cable.What are you using as a preamp?C-4? Either that or a cracked solder connection on the M-4's input RCA's. I just finished up a C-65 that had a bunch of bad solder connections that was causing another M-4 to do the same thing as well as my test M-4 .
 
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with no pre-amp hooked up to the amp the speaker A only has the problem. If I turn off the speaker A the problem stops and there is no problem with speaker B side.

Bob
 
Do you have speakers connected to both A & B.? Does it do the click click thing with the speakers unhooked?
 
avionic said:
Do you have speakers connected to both A & B.? Does it do the click click thing with the speakers unhooked?
Click to expand...

Just speakers connected to the A posts. No pre hooked up, when I power on wait for the power relay to set then push the button for speaker A - click click click... only on the speaker A - B side doesn't do it. I've not done the just change to speaker B pots yet tho. If it's the speaker relay, is there a fix for that or some way to trouble shoot that?

Bob
 
Speaker pair A, or does speaker A = Left?
If it's speaker pair A, there is no reason that the relay should act differently, unless the Speaker A selector swith is dirty. It's the same amp channels driving speaker A and B.

If the relay is toggling while playing music to speaker pair A, but when A is disconnected and another pair of speakers plays okay on B, then it sounds like a wiring or speaker problem on the A set.
 
Okay I swapped speaker wires to the B channel both L & R the click click followed the speaker hookup.

With no speakers hooked to the A side - no problem.

This is with no pre hooked up, just speakers and power on.

As soon as I activate the speaker B button the problem starts.

thanks for all your input.

Bob
 
Maybe the loud hum damaged the speakers and now they're loading the amp too much. Do you have another set of speaker to try?
 
If it click clicks on both A and B with the speakers attached .Then you have probably damaged one of the two amplifier modules or you have a shorted speaker or speaker wires are shorted.Finding or verifying the speakers and wiring should be easy enough to do with a multimeter--even a caveman could do it:D
 
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A little more trouble shooting....

Ok I had some time today swap cables,check speakers and pre-amp.

Here's what I have so far:

Left speaker fuse blown

OK un-plugged left speaker

no more click click

sounds good - right channel with right channel meter working - noting on the left channel meter.

swapped pre inputs - still good on right channel nothing on the left even after swapping good right speaker into left speaker outs.

So I've got one good channel and one speaker fuse blown.
Going to the shack tomorrow for a new set of fuses.

I looked at the fuses in the amp and they "looked" good - I forgot to check them with my DMM.

Any comments and suggestions would be MOST welcome.

Back to cheers,

Bob
 
My best guess at this point is a blown output or two in the left channel. Pull the four outputs from the left channels heatsink and check them with a multimeter for shorts.Toshiba's 2SC2460 and 2SA1050..
http://www.audiokarma.org/forums/showpost.php?p=3203663&postcount=7
May even have a situation similar to this. But the fact that it continually clicks tells me there is still relay contact continuity.
 
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When you hook the working speaker up to the left channel. Do you hear the relay click one time?
 
avionic said:
My best guess at this point is a blown output or two in the left channel. Pull the four outputs from the left channels heatsink and check them with a multimeter for shorts.Toshiba's 2SC2460 and 2SA1050..
http://www.audiokarma.org/forums/showpost.php?p=3203663&postcount=7
May even have a situation similar to this. But the fact that it continually clicks tells me there is still relay contact continuity.
Click to expand...

I haven't checked the output transistors yet but where did you source yours the last time you bought some.

2SA2460 and 2SA1050

Thanks,

Bob
 
Vint Age said:
If it were me I'd want to check the speaker out very carefully. The blown fuse and the fact that your amp goes into protection mode when it's connected says that there's something not right going on there. :scratch2:
Click to expand...

That speaker has already taken out a channel...
 
bobrown14 said:
Here's what I have so far:

Left speaker fuse blown
Click to expand...

If it were me I'd want to check the speaker out very carefully. The blown fuse and the fact that your amp goes into protection mode when it's connected says that there's something not right going on there ... :scratch2:
 
avionic said:
That speaker has already taken out a channel...
Click to expand...

Operator took out the amp channel - blew the speaker fuse but the speaker is now fine, amp not so. On 2nd listen, I think the Emits took a dump in the affected speaker as well. Going to have to check the resistors on the crossover and see if one got burned out.


Avionic - would there be some possible burnt resistors that go with the transistors in the amp? Also this is going to be a "while I'm in there" question. Which caps would you suggest need a refresh?

I will take out the transistors and check and replace over the holiday.

How this happened was I had to change out pre-amps (low output in one channel) and forgot to hook up the 2nd TT on the pre. Was fiddling around hooking that up with the power on and knocked a cable loose on the amp. Note to self: turn off the power, no matter how easy a fix. I had turned off the pre and left the power conditioner and hence the amps powered up, and oh yeah if I'm drinking beers make the change at some later date but for sure not tonight.

The really crappy part is that the C-80 pre only really has only one MM cart input - my 2 tables are MM and the 2nd phono input is only for MC carts. I should have stepped back away from the rack after seeing only one ground post for TT hookup (a suggestion that the pre is designed for only one type of TT). That is not a set in stone thing but it should have at the very least made me take a look at the manual.

2nd note to self: Read the owners manual to refresh my hookups.

The ONLY good thing about this is my backup to the M-4 is a Crown PSA-2 - not to shabby for a backup amp. But I gotta say the M-4 had the lean on clear sound. The C-80 pre is alot more colored than the Technics SU-9070 I was using. The Technics pre is old, my like 3rd one that I've tried and they all have tired out with various issues.

Cheers,

Bob
 
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Avionic - would there be some possible burnt resistors that go with the transistors in the amp? Also this is going to be a "while I'm in there" question. Which caps would you suggest need a refresh?
Click to expand...
Possibly some resistors.But usually it just takes out the outputs.Capacitor replacement.....All of them..Is my SOP.This amp is 30 years old. Electrolytics don't age well.
 
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