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

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 ?

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

Thanks all for your ideas and responses. I did get a lead to a former
AR Employee, Alex Barsotti who works now for AB Technical Services in
Worcester, MA. He happens to have the exact replacements in-stock,
can't ask for any better. Yes, there are some differences between it
and the 2N3054, such that the more common unit *will* work some of the
time, but not all of the time.

I will try the added resistor trick before changing out those that are
in there now, but as they are on sockets, even a change-out is the
work of a few moments.

Thank you, Bruce, Roy and finally Alex for getting involved in this
tiny little request.

Peter Wieck
Wyncote, PA