well, I was out and picked up a footswitch anyway. It switched from a to b with the foot switch although at first it flickered between the two so it looks like I may need to clean up some solder joints as well.

but, still no sound out of the b channel. but, I expected that.

On a side note I was wrong about one thing. I thought I could hear static on the b channel but the house was quieter today and with the a cranked full you could hear the static (white noise) nice and clear and the B channel .......nothing. So it could be in the amp section... I was hoping not.

now I have to get the meter out an start tracing 

I get to leave the house today to run a couple errands so i will swing by GC an see if they have any cheap footswitches.

and this may sound dumb, but what does "stuffed" mean? do you mean there might be something actually jammed in the socket?

had a few minutes while the boy napped and I was able to check a couple things. the light does switch to the B channel.

Also I noticed (don't know why I never checked before) that A and B channels both have a light hiss with no signal plugged in. So that should mean the amp section in the B channel is working and that it's somewhere in the preamp signal path.

Quote from: DrGonz78 on August 04, 2014, 03:49:05 AM
Hopefully file is not too big... lets check...

Thank you for the file, this should help a bunch.

I do not have a foot switch to try so I have never tried that. I believe the light changes when a/b is switched but I will have to double check.

The baby will go down for a nap in a bit and I can mess with it then.

And as far as pedal go vs. repair.... I picked the head up so cheap that was my thought at first but after having the head for a few yrs its just bugging me so i thought why not at least take a look.

I have done alot of googling on this amp head and I found out alot, but I still can't find some stuff.

I'm trying to find the schematic and user manual for it. I found on yamaha's website the manual for the III but no info for the II.

I picked it up a few yrs back and most of it works. I picked it up cheap because the B channel does not work at all. I had used a pedal with it but since PCSed a few yrs ago I haven't even played it.

The clean channel sounds great. But I decided maybe it's time to try figure out what's wrong with the B channel.

While I'm not an electronics guru, I did go to college for HVAC so I am familiar with wiring diagrams and working on things. I also build guns and cars and do everything from welding and machining to finish work. I have also been into car audio since before I could drive and built my own crossovers. Basically I like working with my hands and don't mind getting dirty and I think I can handle this project.

Does anyone have a source for a schematic? and/or any tips on troubleshooting this beauty? I'm hoping it's a simple fix like the A/B switch but I need to start tearing into it.

thanks for any help
Leon