Hi Bill
Well I suppose I should have guessed it - Fluke are probably the # 1 when it
comes to DC 'Standards' I had never encountered an HP-735 before and this
one is in overall good condition - I will complete the restoration and keep
it as a 'collectors item (its not too big!) As for the fluke range, I have
two 731B's and better, a Fluke 732A which has been running non-stop for more
than a year - it now reads the same on my HP 3458A , which is still in
calibration. I agree that the Fluke 731B is a good standard for its size,
pity about the 'poor' battery back-up circuitry, and the NI-CADs which have
damaged so many. The other shortcoming was the rotary switch - it would have
been better with a set of terminals for each range.
Regards
Roy
From: wb6bnq
selection
-----Original Message-----
Sent: Monday, May 18, 2015 10:29 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 735A DC Transfer Standard
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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