On Nov 13, 12:27 pm, "N Cook" wrote:
wrote in message

ps.com...





Apparently made by Signetics, marked as follows:

AMP2947
6808

I find no cross for it in my ECG book, can't find a direct reference
on-line. This is the driver transistor for a vintage-1971 AR
integrated amplifier. The outputs are 2N3055s.

Their schematic lists in parenthesis (2N3054) which physically fits,
but gives quite a distorted output. I matched two 2N3054s with very
low leakage and matching Beta, got distortion. I used two "stock"
transistors from another amp, worked just fine. Which, by the way,
closely match on my tester the parameters of the 2N3054s... go
figure.

Thoughts? Ideas?

Thanks in advance.

Peter Wieck
Wyncote, PA

if signetics then presumably 1968 , could it be Ge ?- Hide quoted text -

- Show quoted text -

Nope, all silicon per AR.

Once upon a time a while back, Mouser crossed this to the 2N3054,
which worked for me in some examples of this amp. But not this
example. One person in another NG suggested that newer-run transistors
are "faster" than older ones - perhaps I should add some small
resistance - I will try that tonight.

I think I may have a very-early-run AR amp so, we shall see.

Peter Wieck
Wyncote, PA