Hi Bob, I also have one of those and its companion Frequency Response test set; hp-739. The attenuator is strictly a high impedance device designed to look into 1 MegOhom or more. Aimed at high impedance meters and scopes. Quite stable for the "day," but could be improved by changing out the Vref tube with a modern zener, like a TL431, in a scaled circuit to provide the proper voltage
I would keep it in tact. Nothing wrong with tube technology. I will email you a 738 manual in PDF. Bill....WB6BNQ Bob Smither wrote: > J. Forster wrote: > > That is not a unique incident. > > > > I'm interested in LASER Interferometry. Attached is a pic I took of an HP > > 5529A LASER head. > > > > (Aside: If anybody is interested, there is a Yahoo Group for LASER > > Interferometer fans) > > > > Note the two leads to CR5 near the top, center of the pic. They go to a > > feedback photocell and obviously have never been trimmed or soldered. > > > > The unit ran fine that for several months before suddenly failing. > > Soldering the leads fixed the LASER head. > > It was not always this way. Today I stumbled on a 1965 HP 738BR > Voltmeter Calibrator at my favorite surplus electronics store. I > offered $20.00 and it was accepted. > > This unit is based on vacuum tubes! I got it home, plugged it in, and > it is still in spec on the DC range. The AC part is not working - I > suspect the small incandescent lamp that stabilizes the oscillator. > > I may end up junking the vacuum tube half. The other part of the > instrument, in a separate compartment, has a precision 40 step > attenuator with a 10^6 / 1 range (300 Volts to 300 uVolts) which I will > certainly keep. > > Best regards, > -- > ===================================================================== > Bob Smither, Ph.D. [email protected] > > Q: What is the square root of 4b^2? > A: To be or not to be. > ===================================================================== > > ------------------------------------------------------------------------ > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
