Thanks, Craig.
 
I've closed it back up for now but I took a closer look at things before I did and I do think the capacitors leaked because what I thought might have been glue extended over a small unshielded jumper wire on the board and the wire was corroded (while the other jumpers looked fine). Perhaps if I can figure out what the part number is on that board I can simply replace it entirely. That transformer is really nasty looking too and should probably go.
 
Also I was looking at the wrong board for the fader pot housing thing. I was actually looking at the 1/4" output/pedal connector housings (silly but I got kerfuzzled). The faders connections are hidden underneath (well above) another board that looks clean but I'd have to remove it to see the other side.
 
Again this all seems modular so if I can find a repair manual or something with model numbers I might be able to fix it myself for relatively cheap.
 
The ironic part is that the battery seems to be like it will be the most problematic for me because it is soldered right onto the board and my soldering iron is meant for heavier gauge wire (not fine electrical stuff). Not to mention the severe case of shaky hands I get when I try to do fine wiring jobs. The battery may be fine though so maybe I'll see if one of my buddies can bring over a voltage meter (sad I don't have one but I don't) and I can test it to see if that ACTUALLY needs to be done.
 
It's weird... in one of the vids I watched earlier the guy actually used a triple AA to replace it which I guess works if the voltage is right. He soldered some leads to it then used a cable tie to clamp it down before closing the thing up.
 
Don't think I'd do that. lol

But I will still see what the local shops might charge. Smaller town though so I'll either get hosed or not be able to even find someone willing to do it. This is one of the things I miss about living in a major urban center.
 
That and the cheap and plentiful cheese.
 

I expect that if you cannot afford a good quality new keyboard, you probably are not in a position to have your machine professionally repaired. Prices for these kinds of services tend to reflect the idea that, like vintage car restoration, money is no object in keeping a beloved antique on the road. In many cases places that offer repairs will send something like this out to a specialist in any case. There are actually only a few parts on these machines that are not off the shelf compatible with standard electronics, although getting actual replacement parts from the manufacturer are a different story. If you have the money there are some possible resources here:
 
http://www.synthmuseum.com/resources.html
 

Looks like parts are readily available, and from what I see the powersupply would be a snap to replace
 
http://www.syntaur.com/yamaha_dx.html
 

 
 
It's a cool machine.  I had a DX7s a long time ago and I love my SY77.
 
 

slartabartfast
I expect that if you cannot afford a good quality new keyboard, you probably are not in a position to have your machine professionally repaired. Prices for these kinds of services tend to reflect the idea that, like vintage car restoration, money is no object in keeping a beloved antique on the road. In many cases places that offer repairs will send something like this out to a specialist in any case. There are actually only a few parts on these machines that are not off the shelf compatible with standard electronics, although getting actual replacement parts from the manufacturer are a different story. If you have the money there are some possible resources here:
 
http://www.synthmuseum.com/resources.html
 

I know if I just bumbled into one of these local places they would certainly go all "boutique" on my arse until I opened my mouth and showed that I "kind of" know a little more than the average droog but then they might get cranky and just refuse to do it. Then again I'm not familiar with these local places so maybe they'll be happy to have something interesting to do. I doubt they get a lot of gear to raid like my old shop does so they'd probably charge a premium to order parts I could order myself.
 
Either way this is starting to look like something I might be able to handle on my own. I just found a vid where the guy talks about a diagnostic mode (which I was unaware of but is probably in the manual) so maybe I can find some answers there. Also he does a more sane battery replacement than the other ones I've seen and shows how a little more detail about how to pull the thing apart (he does a chip replacement).
 
http://www.youtube.com/watch?v=X8Pdc3_7LMU
 
So I'll have to see what that diagnostic setting does. Maybe I can clear up the bizarre LCD display at the very least.
 
Cheers.

cityrat
Looks like parts are readily available, and from what I see the powersupply would be a snap to replace
 
http://www.syntaur.com/yamaha_dx.html
 

 
 
It's a cool machine.  I had a DX7s a long time ago and I love my SY77.
 
 

Awesome!! Gotta love this older gear that can actually be fixed. I do not like the current electronics philosophy of "build it cheap and unserviceable... THEY'LL JUST BUY ANOTHER ONE!!!"
 
Thanks for the tip.

Well that parts site showed me that the residue around the capacitors is normal so it likely isn't a leak. Still the corrosion on the jumper on mine is obviously not right. Sloppy glue job I guess and perhaps  the glue has corrosive properties or reacted poorly to humidity or something.
 
Very educational. Cheers.

If the lcd display garbage means patch data is garbled, then there's no telling what kind of noise would come out of the FM engine. Could explain the noise you heard. Factory reset might put good data into the patches; your old ones are gone.
 
I put the E! mod in my original DX7. It fixed the velocity range, improved midi, and enabled a ROM slot for putting in many banks of patches. Also, made it easy to use the keyboard as a controller, switching channels and the like. It's on the shelf now, and my guess is it might act like yours if I plug it back in.

bvideo
If the lcd display garbage means patch data is garbled, then there's no telling what kind of noise would come out of the FM engine. Could explain the noise you heard. Factory reset might put good data into the patches; your old ones are gone.
 
I put the E! mod in my original DX7. It fixed the velocity range, improved midi, and enabled a ROM slot for putting in many banks of patches. Also, made it easy to use the keyboard as a controller, switching channels and the like. It's on the shelf now, and my guess is it might act like yours if I plug it back in.

I was actually wondering about doing a factory reset. I bought this thing used and IIRC at one point was hamfistedly screwing around with changing the banks. I have no idea what kind of crap could be in there and honestly I'd prefer a reset anyway.
 
I've heard/read about those mods but don't think that was done to this one. That involves a specific daughter board being installed, right? I do not see one of those.
 
I'll try to find out how to reset it and I just found a vid on doing the diagnostics (neither of which seem to be in the manual).
 
The noise however is a very loud/scratchy hum and then playing with the volume fader caused SERIOUS pops/crackles (I had to test my headphones to make sure they weren't blown it was so loud).
 
There is another possibility and that is the headphone jack is screwed up somehow. I never used headphones with this thing before today so maybe I'll try it with one of my beater practice amps. Still wouldn't explain the garbled screen.
 
I think I'm dealing with multiple problems but thank you for letting me know about the Reset option.
 
Cheers.

I also gotta wonder how much the internal stuff is interconnected with the MIDI out. Like maybe even if it won't work as a standalone keyboard I wonder if it would still transmit MIDI data to Sonar which is the primary function I'd like to use it for. Hmmm....