Schematics/Service Manual for Yamaha C1

ethan at ethan at
Fri Jul 10 18:34:29 CDT 2015

I'm just going to toss a feeler out there. One of my more recent most 
sought after machines was the Yamaha C1, a 286-12mhz MS-DOS "laptop" with 
11 midi ports.

I picked one up off of ebay, not cheap in it's non-working condition. I'm 
now working on getting it running.

I'm looking for schematics or service manual. It's a long shot :-) I 
contacted Yamaha of USA already and they said they don't have 
documentation going back that far. Both paper or digital.

My unit when powered on never seems to do a floppy seek, or boot. Caps 
lock and num lock don't trigger the LEDs. And it has an internal or 
external display dip switch. The unit always comes up set for external 
display, even though dip switch is set internal. I hunted inside and found 
9 electrolytic caps were leaking. I cleaned up the mess and replaced them, 
but still no go. The traces I can see that look on the fence all 
continuity test okay.

I have more caps on the way to replace all of the capacitors, and next 
step will be to look at the power supply output on an oscope to see how 
good or bad it looks.

I have already archived the eprom data, and will be scanning all the 
documentation and archiving the floppies. I will make it all available 
online. I have some of the programming docs, some dip switch info, pinouts 
for the expansion connector (but unfortunatly no hard drive controller 
connector afaik) and more.

Schematics would be good to go with that, as the mainboard has more than 2 

Ethan O'Toole

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