Re: Advice for a sick DC505a- discovered a mainframe issue as well.


On Fri, 25 Dec 2015 20:45:28 -0500, you wrote:

On 12/25/2015 7:12 PM, David [TekScopes] wrote:


A couple of the 2N3565 transistors in mine were bad and about half
were "soft" on my curve tracer so I replaced them all.

Hello, David--

Thank you for your extended repair suggestions. I'm uncertain what you
mean by the 2N3565s'
"soft" characteristics-- were the V-I curves drifting as the
transistor(s) under test warmed up?
They had poor (high) collector to emitter saturation voltage and poor
(low) collector resistance.

How did the replacements look on the curve tracer, and were the
replacements made by
the same manufacturer as the originals? IIRC, a Fairchild 2N3565 has a
round grayish-colored
bodies topped by a dome of black epoxy. Again IIRC, some 2N3565s are in
conventional TO-92
There was nothing special about the application of these transistors.
I used 2N4401s as replacements but 2N3904s will work and 2N5088s would
be ideal.

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