Vintage Synth Repair

--- In vintagesynthrepair@yahoogroups.com, "Quazimodo" <noddyspuncture@...> wrote:
>
> Hi guys,
> 
> I have a Delta and recently the TOS (top octave synth) chip has gone. It's the AY-3-0214. I replaced it with the retro version - the KS-196 details can be found here:
> 
> http://www.organservice.com/crm/topdividers.htm   <show in 'figure8' scroll down to just over half way>
> 
> This chip is (supposedly) an exact drop in replacement for the AY..!
> 
> Anyway, she started to sing again, but the tuning seemed way off. 
> 
> Switching to either setting on the transpose switch keeps all the relative pitches up and down the keyboard OK, but play the same note and switch the transpose - and the jump was not an octave. Sometimes, on initial switch on (cold) it would be the same note and then, as it 'warmed' up the interval would open up slowly but never actually reach the 'octave' spread.
> 
> Looking at the schematic there are two 4000 series CMOS just before the TOS. A 4013 and also a 4069. Today I changed both these and now things have improved (changed?) somewhat.
> 
> In the 'UP' setting of the transpose switch I am getting normal, and in tune behavior. It tunes and stays there solidly. But when I switch to 'NORMAL' (the low setting) it plays roughly a minor third sharp. So a C plays as an Eb.
> 
> One symptom I just noticed is that when I am in the 'NORMAL' position with the octave switch (minor 3rd sharp) and I touch and press on a chip on the retro KS-196 small circuit board, I can lower the pitch and actually bring it perfectly in tune as it should be. As soon as I remove my finger though it's straight back to where it was.
> 
> Would anyone here have any idea where I should look next or what the problem might be please?
> 
> Cheers,
> TOM
>

Hi tom,

If there are any ckts using a bi-polar supply scheme( and part of the ckt you're working on), check to see if theyre where they need to be 

ie; +/- 12 or +/- 15 volts