Vintage Synth Repair

I truly had a great day. I replaced a 1Kx4 RAM and resolved my 
computer problem on my P10. Now all LEDs light up and the unit 
behaves somewhat functional. Upon turn on the unit goes to tune cycle 
then all LEDs light up and entire panel is functional. Still no sound 
but this is a great milestone. Two problems I see are sequential 
board is dead which I think I'm on top of. This is PCB9 which I over 
voltaged when I put the 12V regulator in instead of 5V (due to poor 
documentation this is an option for tape or wafer drive). I think 
this will be easy to fix but I was hoping to help on one clue. There 
is a window showing voices 1 thru 5 and below 6 thru 10. The top 1 
thru 5 show 1,3, and 4 LEDs on continously never changing. The bottom 
6 thru 10 change as I hit the keys as if it is responding however LED 
7 never comes on. Can someone offer advice. I have 4 CEM3310s out on 
the top voice board. It is to my understanding I may get a noise out 
if configured right to see functionality before I buy expensive chips.

Sorry long but I am very happy to be at this status. Can sequencer 
shut down operation. Was curious, should I get sound without 
sequencer.



--- In vintagesynthrepair@yahoogroups.com, "Frank Simon" 
<fsimon001@...> wrote:
>
> I did find a chip pulling down DB4 on U311 it is a 6514 4K CMOS 
RAM. Thank god for IC sockets. The only problem I'm a little confused 
on a cross for it. It appears obsolete. It is called D444C on the 
chip and 6514 on schematic. Can anyone offer advice on a cross.
>   ----- Original Message ----- 
>   From: fsimon100 
>   To: vintagesynthrepair@yahoogroups.com 
>   Sent: Friday, May 30, 2008 8:58 AM
>   Subject: [vintagesynthrepair] Prophet 10 dead
> 
> 
>   Was curiouse if anyone can offer help. I bought a dead P10 no 
lights 
>   or anything. The processor is good. I put logic analyzer on 
decoder 
>   output and see ROM1 (Y0) and RAM (Y5)(which I believe is the 
scratch 
>   pad memory)active at start up. All address buses and Data buses 
are 
>   active. I am not certain the algorithm. A flow chart would be 
nice or 
>   some help with what I should see at some critical points. I am 
>   wondering if there is a chance the ROMs lost programming and how 
would 
>   I know. Even if they did shouldn't lights and/or display come on. 
And 
>   yes the power supplies are good.
>