Re: HP8640B RF Fails Several Seconds After Power Up
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Also of some vague relevance.......
On Wed, Apr 13, 2022 at 2:52 AM Arie de Muijnck < mygroups@...> wrote:
On 2022-04-13 02:16, Flannel Tuba wrote:
Greetings,?
I am finally getting back to this project and have narrowed the
problem to a failing transistor in the A3 Main Oscillator.
Fortunately this is a relatively easy part to get to once you
know its secret hidey-hole under the large hex cap on the top of
the oscillator body. (See this OCRed article from the Sept/Oct
2005 QEX magazine:??and
search for HP8640 There's a marvelous description of how to
disassemble the A3 unit to get to the electronics, and how to
spot one of the most common problems -- loss of either +20v or -
20v at the Q1 transistor socket).
Anyway, having found the main oscillator transistor A3 Q1, and
demonstrating that it was failing using a Huntron curve tracer
(and some freeze spray!), I am now looking for a suitable
replacement. The HP part number on the parts list is 5086-7082,
whereas on the schematic itself, it's listed as 5086-4282.
So can anyone direct me to an equivalent to either a 5086-7082
or 5086-4282 NPN transistor, or a spec sheet that I can use to
try and match the original?
Thanks,
Scott
Thanks for the link to that great archive! A direct link to the
article as PDF is here, at page 35:
??
Arie
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