Discussion about the Korg PolySix synthesizer

Andy,

I am in Portland OR. If you saw the last post which I deleted please ignore had bad readings. In fact the very first post you responded to had bad readings I apologize I just realized I was reading the IC pins incorrectly and have now corrected myself in these readings... boy it has been a few years since I have worked on a project. 

Well I ordered a few replacement parts from a company in Canada and Farnell. I installed a new LM13700 at IC 20 and 21. This is because I was still working with the salvage LM13600s and wanted to rule them out. Next I got a hold of some stock new A798s for Q3 as you had mentioned a possible short at that point. So Q3 is now new stock.

I am still getting the 50Hz and it is still 3.8 peak to peak (I have my scope
set at "1" for the Volt/DIV and I am getting an amplitude of -1.9 to 1.9 or 3.8
pp)

V2 and the panel have no effect on the voltage.

Did a new test of points as before:

IC13 pin 7 = 4.8v
IC16 pin 7 = A square wave 15v to -15v 10msec
IC19 pin 12 = A saw wave form at 4v to 4.5v
IC21 pin 12 = 50Hz 3.8vpp
Q1 Source +15v Drain is a 50Hz 12vpp

I am still at a loss and trying to track this problem down. I may have to coax
Jed over if he can spare the time ;)

- Daniel


--- In PolySix@yahoogroups.com, Andrew Jury <andy@...> wrote:
>
> Hi Daniel,
> 
> Sorry for the delay, have been working on some pressing stuff. Can you let
> me know how you have been getting on. If you are still stuck at this point
> let me know and I will get the readings for you this evening. Lunchtime
> where you are?!
> 
> Cheers,
> Andy