Discussion about the Korg PolySix synthesizer

Hi,

IC34 SSM2056 is NOT the VCA but the EG. The VCA is built discretely
by transisotrs Q5, Q6, and buffer amp IC33. Nevertheless IC34, acting
as EG, could be the reason for different levels between voices,
although I dont think that this is rather likely when it works
otherwise. The VCA adjustment may correct or compensate the problem
and it is not necessary to do it with an oscilloscope. If you just
want to set the same level on all voices you can do this with a DVM
in AC setting, provided the DVM has low voltage setting in AC; many
cheapos do only have mains voltage range, though. You can measure at
the headphone output; it has the highest voltage level (several Volts).
OR: use your ears!

Good luck!

Johannes


Andrew Jury wrote:
> Hi TR,
> 
> As suggested by CJP you might have a problem with the VCA circuit. 
> The VCA heart is an SSM2056 chip which is at position IC34 on the 
> voice board (KLM-366) on the right-hand side with the top panel up. 
> As an initial check you could try switching the VCA chips from one 
> voice to another as they are socketed and can be removed without 
> soldering. There are six in total, one for each voice. If you swap 
> one and the problem shifts from one voice to another then this might 
> be the issue. However, if you own an osciloscope (or know someone who 
> does) I would suggest you check the VCA adjustment in the service 
> manual (let me know if you can't find a copy). This involves 
> adjustment of pot VR9 and comparing output waveforms. If you find you 
> need to replace IC34 I have seen them for sale on eBay or you could 
> try my old friend Senso at vintageplanet.nl
> 
> Also, the SSM series chips are CMOS based and sensitive to static 
> electricity. Make sure you take the precautions to earth yourself 
> before handling the internals. Drop us a line if you need any more 
> help...
> 
> Cheers,
> Andy
> 
> --- In PolySix@yahoogroups.com, "toerag_man" <toerag_man@...> wrote:
>> Hi, 
>>
>> Every sixth note I play is louder than the rest. Is this a common
>> problem? Easy to fix?
>>
>> Thanks,
>> TR
>>
> 
> 
> 
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