Author Topic: OT: strange symptom  (Read 1231 times)

Gil

OT: strange symptom
« on: October 17, 2003, 04:19:43 AM »
I have that Kawai analog synth that had it's nicd battery leaking... leaving green acid over a one inch square area over the main PCB.

It at first just played it's own notes automatically and randomly.
After I cleaned the area it stopped playing automatically and started to somtimes play double notes when you hit only one key... I had it replaced a few parts where the defective area is including the battery itself, and validating all connections are still conducting.

The problem is that after I replaced 3 electrolytes, it's dial wheel has stopped to respond ! of course I tried to reverse the operation but no success. There is no sign of polarity for those caps on the board but I double and triple checked that they are put correctly.

Now, I found sometihing strange -
there is a short between a transistor leg, BUT it doesn't come from the tranny (it's ok) and it is there ONLY when the synth is powered up, and for a few seconds after I power it off.

The same occurs between two other spots, of two components that are placed near each other.

Another sympthom that I don't know if is normal, is the main chip (made by intel at '82) and the EPROM chip that are getting a little warm when the synth is ON.

Do you have any clue what type of problem is causing this ??

What shuold I check ??

Thanks all !!