[sdiy] Buffered/unbuffered CMOS in Oberheim logic boards

[Dave Manley]

After looking at the schematics I didnt think you'd have a problem since it was all standard digital logic design except maybe where inverters were used in RC oscillators.  IIRC there was also a couple of places where caps were added to stretch pulses.  I suppose the output current rating on biffer vs unbuffered could affect the time constant but perhaps it isn't critical.

-Dave 

-------- Original Message --------
 From: g m montalbano <montalbanogm at gmail.com>
 Sent: Tue, Aug 7, 2012 04:24 PM
 To: Magnus Danielson <magnus at rubidium.dyndns.org>
 CC: synth-diy at dropmix.xs4all.nl
 Subject: Re: [sdiy] Buffered/unbuffered CMOS in Oberheim logic boards

>I ended up rechipping all of the overhead board and about half of one
>of the channel boards, using buffered CMOS -- and the circuit works as
>it should.
>So, for future reference, in the case of Oberheim 4-voice keyboard
>electronics, unbuffered A series chips are not necessary.
>
>~GMM
>
>
>On Sun, Aug 5, 2012 at 4:43 AM, Magnus Danielson
><magnus at rubidium.dyndns.org> wrote:
>> On 08/04/2012 10:02 PM, Dave Manley wrote:
>>>
>>> Unfortunately the answer is probably 'it depends'.  If used strictly for
>>> digital functions then using buffered gates is (probably) ok.  If the old
>>> timers were doing some oddball analog weirdness only possible with
>>> unbuffered gates, then no.  Are there schematics?
>>
>>
>> Some parts of the logic may also depend on the gate delay of individual
>> parts for proper operation.
>>
>> Then again, there are places where you can fit new stuff in without any
>> issue at all.
>>
>> Schematics is available.
>>
>> Cheers,
>> Magnus
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