Yamaha EMX512SC

[Jazz P Bass]

I see no mention of the health of the + & -15Vdc supplies.

You do know that these EMX amps have a ground scheme from hell don't you?

All of those shiny pieces of spring foil inside of the cover have a purpose.

[Jazz P Bass]

Here is a pdf file of a MEF member that documented the grounding scheme.

[lowell]

My bad. The 15v supplies are both good as well.

Yes all those foil pieces...what a PITA. So are you saying that could be why? Because the thing isnt screwed together?

[Jazz P Bass]

I don't Know why.

What I do know is what myself & the gentleman that posted that pdf file went through on one of these amps.

The amp will not function properly unless All of the ground points are connected.

I had one of these beasts 99% back together & there was a ground connection missing at the output panel.
It didn't like that.

[lowell]

Here is a pdf file of a MEF member that documented the grounding scheme.

http://music-electronics-forum.com/a...o-emx512sc.pdf

That is... crazy. Ok lemme see if I can follow it and bring it to life.

[lowell]

Jazz, and the guy who documented the grounding: I want to marry you both.

So indeed this worked. The thing powered up and stayed up. However, I still had no speaker output. As if this wasn't a difficult enough repair already. So got out the scope and found no signal out of the IC101 opamp. Checked and found no +15v supply. The dang ribbon cable wasn't making good contact on the SMPS board. I ended up having to put a bead of solder on the wire so it was a tighter fit in the clip. Phew. Things working completely now.

Ok, so now for step 67. Lets see if I can get the dang thing back together right, and without disconnecting something in the process. Anyone have a direct line to NASA for support?

[Jazz P Bass]

(281) 483-0123

NASA Johnson Space Center

[lowell]

Got the thing back together and functional. Thanks for the help!

[Jazz P Bass]

Glad that you got it.

And thanks for the conclusion.

[lowell]

You got it. Couldnt have done it without your help. On to the next victim.