I recently acquired for cheap an old HP 740A DC standard/voltmeter of 1960s vintage. It seems to be pretty clean inside and complete except for missing a small bias cell. I'm trying to find a manual - found the "B" version one so far at hparchive. Before putting in much effort to fire it up, does anyone have opinions on whether it's worth keeping and fixing - does it have decent performance by today's standards, so to speak? There's a sticker inside that showed that (sometime in the 1960s) the reference deviation was no more than +/- 5 ppm recorded over a four week period, under some kind of test conditions. Ed

Here's the introduction article http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1965-05.pdf Being a collector of various instruments, if I had it would be keeper. But only for its context of a 1960's instrument. If you plan on playing with it, you will want to make sure the dual oven works, like many ovens of that time and even later it more then likely is not fail safe. It can stick 'on'. It would be interesting to see how much the zener has driffect in 40+ years. The missing bias cell can be replaced with an IC reference. -pete On Sat, Oct 13, 2012 at 2:49 PM, ed breya <eb@telight.com> wrote: > I recently acquired for cheap an old HP 740A DC standard/voltmeter of 1960s > vintage. It seems to be pretty clean inside and complete except for missing > a small bias cell. I'm trying to find a manual - found the "B" version one > so far at hparchive. > > Before putting in much effort to fire it up, does anyone have opinions on > whether it's worth keeping and fixing - does it have decent performance by > today's standards, so to speak? There's a sticker inside that showed that > (sometime in the 1960s) the reference deviation was no more than +/- 5 ppm > recorded over a four week period, under some kind of test conditions. > > Ed > > > _______________________________________________ > 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.

Pete I read this item with considerable interest, as an "old timer" I still have considerable pleasure in restoring some of 'yesterdays' items of equipment. I recently acquired a "DC Absolute Voltage/Current Standard", Model 401A, made by WESTON-ROTEX. This had come from a shut down Laboratory. Much to my surprise it still operates and is very close to Calibration. Again, judging from the components inside, this is probably a 1960's manufactured item. It would appear that Weston- Rotex disappeared some many years ago. I was aware of the Weston Company, because they were well known for their 'light meters'. Would anybody have any further information on this elaborately made item of Lab. Standard equipment. Roy Phillips. -----Original Message----- From: Pete Lancashire Sent: Saturday, October 13, 2012 11:05 PM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] HP 740A Here's the introduction article http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1965-05.pdf Being a collector of various instruments, if I had it would be keeper. But only for its context of a 1960's instrument. If you plan on playing with it, you will want to make sure the dual oven works, like many ovens of that time and even later it more then likely is not fail safe. It can stick 'on'. It would be interesting to see how much the zener has driffect in 40+ years. The missing bias cell can be replaced with an IC reference. -pete On Sat, Oct 13, 2012 at 2:49 PM, ed breya <eb@telight.com> wrote: > I recently acquired for cheap an old HP 740A DC standard/voltmeter of > 1960s > vintage. It seems to be pretty clean inside and complete except for > missing > a small bias cell. I'm trying to find a manual - found the "B" version one > so far at hparchive. > > Before putting in much effort to fire it up, does anyone have opinions on > whether it's worth keeping and fixing - does it have decent performance by > today's standards, so to speak? There's a sticker inside that showed that > (sometime in the 1960s) the reference deviation was no more than +/- 5 ppm > recorded over a four week period, under some kind of test conditions. > > Ed > > > _______________________________________________ > 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.