Vintage Synth Explorer Forums

I bought this on ebay a while ago (paid $250 for it) so for the price I guess I can't expect much. The problem with it is, if I plug it into mono 1/2 or phones (with headphones) I get a weird distorted sound, but if I use output 2 the synth sounds normal. Anyone have any ideas on what it could be (blown channel 1)? If I just use output 2, I would assume that any stereo sounds, won't be right? I will get it repaired, if it isn't an extremely expensive fix. Or just use output 2 depending on how much I would be losing in sound output.

p.s. I cleaned the sliders with tuner cleaner/lube, didn't help.

Welcome to our crazy little site.

Here's the SY-77 hard reset:
NOTE::: ALL USER PATCHES AND SEQs WILL BE ERASED !!! BACK-UP FIRST !!!

Press and HOLD "VOICE"
Press and HOLD "BANK D"
Press "8"
Release all
Let the test run.
Press "COPY" to re-load factory sounds


If this dosen't help, maybe time for a tech. Yamaha 77/99 are pretty crowded inside.

Per schematic:
Looks like ICs 10, 11 and 12 handle the #1 outputs and phones. If they all check out, maybe a DAC problem.

I did the factory reset option at the end of the test mode, no option to push copy to reset, no change.
Here is a video I put on Youtube demonstrating the problem, played first with just output 2 (no problem voice satin bell, just the satin part on 2) then with both outputs 1 and 2 (bell sound on 2). When I play on it stacotto (not on video), it plays fine til after the last note where I get this crashing sound on output 1. If I hold the keys down longer I get the sound also, more often in the lower register. Something to do with after touch?
The I.C.s you mentioned, are they soldered, or pushed into slots, and are they readily available?

sounds more and more like a DAC problem. Most chips are soldered in.

Does it do it with the FX bypassed? There's an FX bypass button on the front panel.

I pushed the effects bypass button, and it worked, so something in the effects is out of whack obviously. I am getting a low internal battery message now, so I will fix that first, and then see where I stand.

The low battery most likely isn't related to the issue at hand. Then again, when you open it up to change the battery you might see something obvious, like a ribbon cable half out of socket or dried crud from someone spilling something in it, which may give you some more information on what to do.

Replaced the battery, low battery message is off, still garbage from effects, effects bypassed sound good.
I looked at the boards when I was soldering in the battery holder, didn't see anything obvious like leaking caps, spills, dust, or loose wiring.

Boo. Is the effects chip socketed? Maybe taking it out and putting it back in may help. Might be time for a tech.

Hello folks. I see this thread is quite old and in the interest of not starting something new that has already been covered I thought I would post my question here. I also have an output issue. Not sure it's a real problem but it is weird. When I plug headphones into the left or right outputs 1 or 2 and move the volume sliders in MULTI MODE, I hear nothing. When I change to VOICE MODE, I hear the sound but it is very low even with the volume all the way up. Can you change the output volume levels inside this machine? Or is this normal? Cheers all.