[sdiy] Buffered/unbuffered CMOS in Oberheim logic boards

Bob Weigel sounddoctorin at imt.net
Wed Aug 8 01:38:02 CEST 2012


On 8/7/2012 5:24 PM, g m montalbano wrote:
> 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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>    
Is this related to the OB8 issue I saw years ago?  Where I began testing 
cmos chips and they measured *BAD* on my chip checker... So I'm tossing 
out this 4001 and that whatever... and as I do the function of the 
machine degrades til it's not even running when I did the clock buffer!  
I threw all the trash canned chips back in there and it worked again 
some!  Still didn't read knobs right...

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