Hi Roy,
I hate to tell you but the hp-735 does not compare to the Fluke 731.
The hp-735 had a drift that was constant. This information came from a
friend of mine that was responsible for the US Navy's Primary DC voltage
standard at their Primary Lab in San Diego, CA in the 1970's. The
actual drift rate I do not recall anymore, but it was significantly
higher than the any drift in the Fluke.
Bill....WB6BNQ
R.Phillips wrote:
-----Original Message----- From: [email protected]
Sent: Sunday, May 17, 2015 4:13 AM
To: [email protected]
Subject: [volt-nuts] HP 735A DC Transfer Standard
Recently acquired a HP 735A DC Transfer Standard. Replaced some caps,
but its otherwise clean and has since been powered. Read a post
recently about a 735A oven failure that included a teardown that
revealed why HP states the oven/ref assembly a non-serviceable part.
The failure in this person's device was the heater, specifically the
thermistor.
Anyone on this board have a 735A in use? Do you keep it powered 24/7
or as-needed? Any failures/repairs/mods?
Best
Nick
______
Hi Nick
I also very recently acquired a HP 735A DC Transfer Standard. Mine
has a Power Transformer with the centre tap 'open circuit' - this I
guess was the result of a failure in the pre-regulator circuit which
in turn caused a resistor to 'burn-out'. I have 'hooked-up' external
positive and negative rails and the unit works, including the oven !
So, I will rebuild this to the later and I think final specification -
which eliminates the 'pre-regulator' circuit. Otherwise the unit is in
excellent condition, in keeping with HP of that period, and probably
superior to the Fluke 731B. I gather that these are quite rare items
now. Let us know how you get on with the 'project'
Regards
Roy Phillips.
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