[time-nuts] Dead 5065A - Some comments - Some questions...

[timeok at timeok.it]

   Ulf,

   what you write and that you have found several dead transistors the problem could be derived from the power supply. When changing transistors and you did the calibrations correctly the HP5065A still does not work means that the initial fault was not found.

   The first question that comes to mind is if the two ovens of the physical assembly are working, you can check this from the meter on the front panel.

   Anything is possible but it seems strange to me that you have two bad A1 assemblies. There are many variables about this repair.

   Luciano

   Luciano P. S. Paramithiotti
   timeok at timeok.it
   www.timeok.it

   Da "time-nuts" time-nuts-bounces at lists.febo.com
   A "Discussion of Precise Time and Frequency Measurement" time-nuts at lists.febo.com
   Cc "Ulf Kylenfall" ulf_r_k at yahoo.com
   Data Sun, 23 Aug 2020 21:06:06 +0000 (UTC)
   Oggetto [time-nuts] Dead 5065A - Some comments - Some questions...
   Greetings.

   Having had my 5065 disconnected several months
   due to all sorts of things, and started it up
   yesterday. It was dead. "Pining for the fjords"

   No 2nd harmonic. Just PhotoCurrent. Quick Phase Checkusing a scope in X/Y-mode returned a "U" instead of a bump
   And most of the rest was noise.

   I have previously replaced a number of transistors
   in A3 (5 -> 60 MHz Multiplier) during first attempts
   to resurrect this unit and it seems like
   the rest of them were gone (how come?) now.
   Many of them are 1855-0327 which I have replaced
   by 2N4416. Q7 by BC557 (!)
   and Q9 by 2N5109. After this, I have adequate regulation
   and an AGC of > 4V.

   All-in-all: Just about every transistor in A3 was bad.
   There were output at first ~ 10 dBm at J8 but it was not
   possible to increase the output by tuning. Also
   there was no AGC.

   I checked a second unit from a scrapped 5065 on my bench
   and the situation was the same with that A3. Low output
   power. No AGC.

   So now for the question before I put any more
   energy in trying to fix the rest of the old faithful:

   I checked the A1 syntesizer unit which did
   provide correct output frequencies but
   they were not as stable as the internal
   5 MHz Osc. (10811) HP does not mention any
   stability/jitter data for A1. Using a 5370B and 1 second
   gating, the output fq was stable down to
   single kHz figures but jittered further down.
   The 5370B counter is locked to a GPS diciplined
   105B and comparing with the 5065's internal
   10811 (in OpenLoop mode), that oscillator
   is also very stable and settable within spec.

   I have two of these synthesizers, but they are
   both the 1st edition using TO packaged
   IC's that are unobtanium. One of my manuals
   shows a more modern unit with plastic DIP's.
   Some signetics and a one-shot that is unidentifiable.

   IF the A1's are bad - has anybody made some
   reverse engineering trying to fit the
   "DIP-version" with modern available IC's
   or modified it in a way that can be reproduced?


   Best Regards

   Ulf Kylenfall
   SM6GXV



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