From: "Michael A. Terrell"
Subject: Re: Looking for equivalent of weird transistors
Date: Thu, 12 Dec 2002 10:59:43 -0500
Organization: Have you seen my bench? No, really! Where is it?
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References: <3DF7A0EC.CB1537CE@mfi.net> <3DF7D4F1.E4F01F5D@mfi.net>
> In article <3DF7D4F1.E4F01F5D@mfi.net>,
> "Michael A. Terrell" wrote:
> > Spehro Pefhany wrote:
> >BIG snip>
> > you an idea of the what the original part was, and then you can choose a
> > part with better specs. I have had to use countless SK, HEP, ECG, and
> What do you mean by "better specs?"
> Remove * from the address to reply.
Sometimes you want a RF transistor rated for a higher frequency or a
lower noise figure. You might need a higher VCEO (Collector–Emitter
Voltage) to reduce failures. A pass transistor that is failing a lot
may need a higher IC (Collector Current) rating. If it is a rare
failure, or one of a kind the replacement info is fairly good. The
biggest problem area these days is Horizontal output transistors. Some
circuits barely work with the original part, and not at all with a sub.
Years ago there were lots of problems with subbing transistors from
the replacement series. Some bad circuit designs used the leakage in
low grade germanium transistors to self bias. When they died, the
replacement wouldn't work because they had lower leakage. You had to
look at the schematic and pick a pair of resistors to bias it properly.
Also, some brands were better than others. ECG was the best, GE was
the worst. RCA had the SK series, and Motorola's HEP line that were
somewhere in the middle. These are gone, along Workman Electronics small
line of subs. Today we are left with NTE, from NTE, and SK, now from
Michael A. Terrell