[sdiy] mystery on-chip matched transistor pair

[Colin Hinz]

Several months back I bought from a surplus electronics parts dealer
a large stash of TV/radio repair parts. This netted me a mind-numbing
quantity and variety of transistors (roughly 500 types of the
2S..... Japanese numbering scheme, alone) and a (smallish) bucket
of ICs. Most of the chips are dull and useless (NTSC chroma functions
and FM stereo demodulators appear in huge quantities) but there are
a bunch of Plessey 8-pin cans with Admiral house numbers. Now, most
Admiral numbers can be cross-referenced to at least an ECG/NTE
number which will usually provide a pinout if not more, but these
suckers.....no dice.

The mid-1970s date codes help a bit. Perusing the 1974 Plessey IC
databook, it would seem that these parts are likely their SL300
series matched pairs. Anyone know for sure? The house numbers are
56C44 and 56C45, though apparently in the Admiral numbering
scheme the 56Axxx, 56Bxxx, 56Cxxx, and 56Dxxx are roughly if not
exactly equivalent. So knowing the cross for any 56x44 or 56x45
would be useful.

How applicable would these parts be for synth use? I put one
on the transistor tester and the Hfe ratio was around 0.95.
That's a single measurement with an Ic of a few milliamps.

thanks,

- Colin


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