Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

Stop me if you've heard this one before...Bought an "As Is" Poly on
eBay. Cleaned it up, plugged it in a lo and behold no display. Sound
is present at the headphone jack about 30 seconds after turning on.
It's a frequency sweep from low to high (sounds almost like the whoosh
of a jet engine starting) followed by constant white noise. This sound
is affected by turning VR1, VR2 and VR3 trimpots.

I'm okay at basic electronic troubleshooting and repair, but have run
out of ideas, so wondering if anyone has had a similar experience. I
have pretty much determined it is not a power supply circuit issue (as
I was hoping when I bought it). All the IC's I sampled are getting
correct power. Also on connector KLM596 CN6A, Pin 6 shows 4.98v, Pin 8
shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
normal and show the power section is working OK.

Unfortunately, I do not have access to a scope. Is it even worth going
any further at this point without one? In a previous post where
someone had a similar issue, it was mentioned that if the RES6.5 clock
was not running this could cause a dead display. I did check RES
5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v, but the
other two are 0v or at least < 1 mv.

Any ideas or suggestions on where to look next?