M406 Mixer Fix Needed!

Yamaha M406 mixer :      Similar to PM170 / 180

The Right Output is dead on the Main Output  XLR, 1/4" and headphone jacks.

The Right output Meter is also dead for the Main Right Output.


Schematics or Service Manual needed.

I called Yamaha and they claim that they have no listing for the Service Manual. Unusual for Yamaha.

Any sort of help with this matter is appreciated.

I do have some electronics knowledge and exprience with a soldering iron and VOM.


Thanks
Matt B
Ontario, Canada

Pics of my M406 showing the PGM R board.
It is the Main Output board for the Right Main Bus. Yamaha calls it the Right 'Program' bus.

It is the card in the middle of the 3 larger ones on the left side of the pic showing the whole unit.

I checked all Resistors. = OK

I swapped the Left output card into the Right output card spot by connecting the Right card connectors into it.

Result: - Main Right output = OK
Headphone Output of Right Main Output = Nothing
Right Meter: Right Output Level = Nothing

Here is the Right Main Output board.  Called 'PGM Right'  (Program)


The 3 pots on the Right card are: from top to bottom:

-Echo Return Pan (FX return)
-Echo Return Level
-Right Program Output Level (Right Main Output)


Matt B

PGM R board

PGM R card

-I did a search of the Toshiba
TA7322P of which there are 3 on each of the output boards.

They appear to be linear style opamps.

See:  http://www.teaser.fr/~amajorel/at203a/ta7322p.html


--If  the problem could be with an OpAmp  maybe I could somehow wire in a replacement - which would of course be non-linear form.

I would need help with how to do this.    I'm not looking for a high-end fix:  as long as it results in something at least as decent as the original sound.


Thanks
Matt B. 

TA7322P