Korg Poly800/EX800 Users

I had a non powering Poly800 when i first purchased it,

while i was getting 9v into the unit, i wasnt getting the +5,-5V to the 
various analog circuits.
Try testing the leads to the joystick for +5, -5V, or if the ex doesnt 
have the joystick, just look for the other +/-5v parts of the circuit 
using the schematic to assist you.

be careful not to fry the cmos by random poking around.

if you dont have those voltages then the problem is in the power supply 
circuit. the schematic is available in the group archive, so could be 
useful for you to trace it down.

I ended up replacing two power transistors that were fried, and all 
came back to life, well nearly all.

I now have a working midi control keyboard, but it looks like the tone 
generator chip is fried. i can enter patches, have reloaded the 
original factory .wav thru my laptop and all details appear in the 
program banks, just no audio.

An oscilliscope over the board shows clock etc is getting to the tone 
generator, but nothing is coming out of it.

Anyone got a dead poly theyd like to donate a tone generator from?

similarly, if your poly was working and now aint, could be the polarity 
of your voltage input? are you sure you are using the same power 
adapter? from memory the poly is -ve tip not +ve tip.

If you follow the schematic thru and see where your voltage is not 
correct in the power supply circuit, you will maybe find the culprit is 
one of those transistors.

Otherwise it may also be leaky caps or other issues, it didnt seem to 
be with mine.

Best Regards,

Marcus Wilson
Research and Development Manager
Sun Industries
33 Guthrie Street Osborne Park WA 6017
Ph: (08) 9244 2200 Fx: (08) 9244 3470
Email: marcus@... Web: www.sunindustries.com.au