[sdiy] looking for a weid antíque IC for a Farfisa organ

[Magnus Danielson]

From: "Antti Pitkämäki" <anpitkam at hotmail.com>
Subject: [sdiy] looking for a weid antíque IC for a Farfisa organ
Date: Mon, 17 Apr 2006 19:53:39 +0300
Message-ID: <BAY109-F20522559609D3F020213C1CAC70 at phx.gbl>

> Hello everybody,
> 
> I have an old Farfisa Professional combo organ. There were a few versions of 
> it, and the model label on this unit says "PP/221". I think it's from the 
> late sixties. I'd really love to fix it, since it has a nice psychedelic 
> "Doors"-kinda sound and it looks great with its ganster-style 
> reverse-coloured gray/white keys and cream-coloured case. One of the 
> problems of the organ is that one of its frequency dividers that it uses for 
> sound generation isn't working. I was planning to replace the two 
> transistors that are used for the divider... Except that it has a weird part 
> there which seems to have all the divider components (2 transistors, a few 
> caps and resistors) inside (I compared the electronics of my organ to the 
> schematics of another version of this organ (PP/222), which seems to have 
> individual transistors and components for the dividers)! So I guess it's a 
> really early weird frequency divider IC. The part is coloured red, has 5 
> pins (or legs), and looks sort of like two transistors combined in a sort of 
> a flat case. Hmm, it's difficult to describe it, I'll take a pic if anyone's 
> interested. The part has the following text on it:
> 
> 200 C 1408
> (2) EG 6840
> PA 745

I would suspect that you have an old General Electric device on your hands. General
Electric used numbers like PA 745 and EG 6840 might indicate that it was made week 40 of
1968. I suspect you have a simple transistor-pair, probably a pair of normal NPNs with
common emitter. This would work nicely as a flip-flop pair in a frequency divider.
I suspect that if you look at the schematics you would find that it would make sense and
that you probably can replace it with your garden varity NPNs or PNPs.

That would be my advanced guess.

Cheers,
Magnus