Vintage Synth Repair

I am looking for some help.  I am working on the Osc. Board of a 
Hammond Piper Autocord 100/730.  Each of the 2 Osc. Boards have 4 six-
stage dividers Hammond # 075-042148.  Generic Equivalent is supposed 
to be PD455.   The original chip was shorted between Pin 7 –5v and 
pin 8 +5v.   The chip also has –25v feed to pin 1.  I order a "retro" 
KS455 which is supposed to be a direct replacement from Organ Service 
Corp, I have also ask them about this issue.  The Retro chip has no 
connection for pin 1 and loads down the 5v supplies if, pin 8, the +5 
is connected.   In the original troubleshooting I knew there was a 
short between the two 5v supplies on the card so I started at one end 
and cut the trace for the +5v feeding pin 8 until I found the chip 
with the short.  With the chip removed the rest of the board seems to 
work Ok.  After installing the new retro chip both the 5v supplies 
were swamped and nothing worked.  By opening the trace to pin 8 on 
the IC in question all seems to work except those notes associated 
with that IC.  I do not have a schematic or service manual but have 
drawn out much of the associated circuit.  There are 6 oscillator 
circuits on the board with two transistors, which I have removed and 
tested in with my tube/transistor checker and they are OK.  

I can't help but think I am missing something.  Any suggestion you 
can offer will be appreciated.  

Thanks

Terry Younce

On Thursday 26 February 2009 05:51:13 pm Terry wrote:
> I am looking for some help.  I am working on the Osc. Board of a
> Hammond Piper Autocord 100/730.  Each of the 2 Osc. Boards have 4 six-
> stage dividers Hammond # 075-042148.  Generic Equivalent is supposed
> to be PD455.

I *did* find that cross-reference info I was looking for,  on another machine.  
In addition to the PD455 number,  other generic numbers for that part are 
S2470 (I'm not sure what make that is) and MC1180L.

Hope this helps,  some...

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