[volt-nuts] HP 735A DC Transfer Standard

[wb6bnq]

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: gilbenl at nickgilbert.org
> Sent: Sunday, May 17, 2015 4:13 AM
> To: volt-nuts at febo.com
> 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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