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@nickgilbert.org > Sent: Sunday, May 17, 2015 4:13 AM > To: volt-nuts@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. > > > _________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. >

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: gilbenl@nickgilbert.org > Sent: Sunday, May 17, 2015 4:13 AM > To: volt-nuts@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. > > > _________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.