• 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

Got a Yamaha M4!!!! But needs work

Just powered it up today and I got 633mV in the left and 0mV in the right. It came out of protect but soon went back in.

I did find out that the Pre-amp in the Kenwood KA-9100 had a problem in the left channel where it would distort and this went on before I connected the KA-9100 to the M4.

Could the pre-amp in the 9100 have messed up the left channel in the M4? Just wondering? I mean, the M4 was playing yesterday afternoon and all this happened when I was moving the amp into my main system and then making sure the offset was down BEFORE I hooked up my JBLs. The amp played for 4 hours on saturday night with the 9100 pre-amp before I was going to move it into my main system. I even had the offset on the left set to 0mV. Looks like I will take the M4 to my tech down in Seattle and have him take a look at it.
 
Last edited:
You should not even have the preamp or speakers hooked up when adjusting Offset and bias...If you are trying to measure offset with a source hooked up your offset will be jumping all over the place.
Set it correctly once then just leave it be. The alignment procedure states " NO LOAD" for bias and offset alignment that means no speakers...
 
Last edited:
avionic said:
You should not even have the preamp or speakers hooked up when adjusting Offset and bias...If you are trying to measure offset with a source hooked up your offset will be jumping all over the place.
Set it correctly once then just leave it be. The alignment procedure states " NO LOAD" for bias and offset alignment that means no speakers...
Click to expand...


Oh, I know not to have the preamp or speakers hooked up when adjusting offset or bias and I did not.
 
Last edited:
Laith, why do you insist on using that damn 9100! Its sick! Give it rest until it gets a new bill of health!
 
Okay, found the problem, haven't tested it out yet.
I pulled the DC balance trim pots and they were fried. They measured less than 100 ohms from leg 1 to 3.
New bourns multi-turn in place.
 
Oh ****, nevermind, those were supposed to be 100ohm variable resistors! It's the bias adjustment that is 4.7k
Doh!
 
Byrd--Tap around on the offending channels circuit boards.Sounds like a broken solder connection/wire or loose connectors..
 
avionic said:
Byrd--Tap around on the offending channels circuit boards.Sounds like a broken solder connection/wire or loose connectors..
Click to expand...

I have it all apart until I can get the rest of the parts in, missed a couple caps in my first look over.
All connections will be polished and treated with Dexoit gold, and I will double check for broken solder joints.
 
Sir.Byrd said:
I have it all apart until I can get the rest of the parts in, missed a couple caps in my first look over.
All connections will be polished and treated with Dexoit gold, and I will double check for broken solder joints.
Click to expand...

Get it figured out yet?Or still waiting fer parts? I would have fixed the problem first.. before recapping the amp.But thats me.:yes:
 
avionic said:
Get it figured out yet?Or still waiting fer parts? I would have fixed the problem first.. before recapping the amp.But thats me.:yes:
Click to expand...

I was going to recap it anyway, and it's not leaving here until its fixed.
Wanted to get the old caps out of there as suspects.

I am still waiting for lha1992 to OK the total and pay me, parts will probably be here on friday.
 
Wanted to get the old caps out of there as suspects.
Click to expand...
:scratch2: Well ..I guess anythings possible.Keep slugging away you'll get'r done..:yes:
 
Is the only way to get to the conductor side lower board really desoldering all of the T-03 sockets???
 
Nope. Just unscrew and remove all 4 output transistors and the CCA will drop out .Keep track of where the 2SC´s and 2SA´s go..Good opportunity to clean off the old compound and apply fresh compound.
 
Last edited:
avionic said:
Nope. Just unscrew and remove all 4 output transistors and the CCA will drop out .Keep track of where the 2SC´s and 2SA´s go..Good opportunity to clean off the old compound and apply fresh compound.
Click to expand...

+1 very easy to do.

Cheers,

Bob
 
Will, hopefully everything is going good with the M-4. Sorry for being on the other side of the world right now. I'll be back in a few weeks so.
 
Okay, got this all put back together.
Finished working on it last night, the thermal putty was very hard to work with, I wish the mouth of the tube was about 10x smaller so I could have gotten it more even. I ended up just cleaning up the excess around the edges rather than worrying about getting it perfect.
So now it is 100% recapped (minus the filters), and has 6 new trim pots, two each for the rail voltage, bias, and DC offset.
 
the thermal putty was very hard to work with
Click to expand...
You just need a very,very thin coating of thermal compound < .25 mm on both sides of the mica insulator.I spread it with a single edged razor blade-First on the heatsink side of the insulator, then on the bottom side of the transistor.
 
avionic said:
You just need a very,very thin coating of thermal compound < .25 mm on both sides of the mica insulator.I spread it with a single edged razor blade-First on the heatsink side of the insulator, then on the bottom side of the transistor.
Click to expand...

Single edged razor blade... now you tell me! :D oh well, next time.
 
Well went to pick up the M4 from Will since its been 2 months since I gave it to him when I went on vacation and powered it on today and it WORKS!!
 
You must log in or register to reply here.
Back
Top Bottom