[sdiy] Unknown VCF PCB

[Andre Majorel]

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.

> 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.

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/