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Subject: Re: [korgpolyex] another dead 800

From: Michael Hawkins <korgpolyex800@...>
Date: 2015-11-28

not necessarily and probably not.

Check for master CPU clock and a whole lot more to check after that to get Poly CPU going. Static memory, EPROM, address bus latches etc. They all need to be checked. The DTC's also.

/Mike

From: "mmdatech@... [korgpolyex]" <korgpolyex@yahoogroups.com>
To: korgpolyex@yahoogroups.com
Sent: Friday, November 27, 2015 8:25 AM
Subject: [korgpolyex] another dead 800

 
Hi,

I got a dead poly800 with a non working
display and power supply sections.

After replacing Q1,Q3,Q18, I got the correct voltages
on all ic's but still no response from keyboard.

The only unusual behavior I can account for is the lack of
signals after the address latch ( IC29 ) in the Y3 - Y7 paths
hence no signals to the keyboard or tone generator IC's.
( IC29's Y0 - Y2 seem to be ok)

The address latch and 8085 pins a13 - a15 were tested and
found to be ok using the 8085 built in binary counter mode.

am I dealing here with a bad cpu ?