[sdiy] Unknown VCF PCB

[Phil Macphail]

> On 7 Jul 2014, at 10:16, Andre Majorel <aym-htnys at teaser.fr> wrote:
> 
>> On 2014-07-05 14:37 +0200, Terje Winther wrote:
>> 
>> However, one of the PCBs was an unknown filter, see this very bad
>> mobile photo:
>> http://www.wintherstormer.no/VCF.jpg
>> 
>> It is marked "VC - State variable filter", and the next line reads
>> "ARTS  85"
> 
> 85 could be the PCB manufacturing year but it looks like it's
> been populated later. I don't remember 1% metal film resistors
> being so common back then.
I think Maplins in the UK started selling 1% metal film resistors in the early 80's but that was very unusual.
> 
>> So my guess is that the top IC is the filter core. However, I have
>> tried all the various suspects: CEM-chips, LM13600/13700, various
>> op-amps, even CMOS-chips, but none of them fits into the required
>> 18-pin required socket configuration.
The SSM2045 was in an 18-pin package, but it would have been a bit of a waste to use it for a SVF.
> 
> Not an SSM2040 or SSM2044 either (DIP-16) or NJM2069 (DIP-22).
> Haven't checked the Roland IR* chips.
> 
> The CEM3372 has 18 pins but pin 18 would be tied to the positive
> supply.
> 
>> Also of note is that leg numbers 5, 7, 10 and 14 on this IC
>> are not soldered in, and consequently not connected to
>> anything.
>> It also seems that none of the legs are in direct contact with +/-
>> 15 volt, so could this IC be some matched transistor device?
> 
> The largest I know are CA3083 and CA3096 but they're both 16-pin
> devices.
> 
> -- 
> André Majorel http://www.teaser.fr/~amajorel/
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy