Discussion about the Korg PolySix synthesizer

Cavernosum, yes I changed IC31 first before I got the scope out, made
no difference. When I probed the CPU's data bus, I found DB1 had very
low amplitude when compared to the other data bits. 

As a test, I slightly bent the CPU's data pins so when I plugged the
CPU back in, they did not make contact with the socket. I probed each
pin and confirmed DB1 still exhibited low amplitude while the other
data bits besides DB1 were valid TTL levels. 

If a defect on the board other than the CPU was at fault my thinking
is DB1 would also drive valid TTL levels hanging in free space. 

My understanding is the CPU has a multiplexed address/data bus so the
data bus must first output the address until it is latched by the
14042s which actually drives the RAM address bus. Do you think this
analysis is valid? 

I have sent my contact info to you in a separate email. Thanks for the
help with the 6514 RAM chip.

Mike 

--- In PolySix@yahoogroups.com, "cavernosum7" <klosmon@...> wrote:
>
> Michael Grossman wrote:
> >Cavernosum, I bought a broken polysix which plays in tune and sounds
> >great except the programmer is flakey. Upon probing IC22-13 (DB1) I
> >noticed the pin has very low amplitude (<2V). I thought perhaps the
> RAM >chip might be bad so I pulled IC22-13 out of the socket and
> confirmed >the amplitude is still low. I am now convinced the
> uPD8048-245 is bad.
> 
> Not necessarily. Have you checked IC31?  On units with battery
> leakage, this is one of the most commonly damaged ICs. Try replacing
> that;  if it still doesn't work, I'll sell you a new CPU.
>  
> >I would also like to buy a replacement 1kx4 static ram (TC5514APL-3)
> if >available.
> 
> Good news:  you can use a 6514 RAM chip and it works exactly the same.
> These can be ordered from Jameco Electronics for about $4 each; 
> Jameco part number 43238.
>  
> ~GMM
>