Frank, Have you got a link to the eevblog Datron 4910 reference element decryption? I have a 4910 and am curious to see what they found, but am not finding any reference to it in their "Episode" list. Thanks Steve On Aug 20, 2013, at 12:01 PM, Frank Stellmach <frank.stellmach@freenet.de> wrote: > Hello, > > until now, nobody has ever reenginered the 732B schematics. Perhaps the bbs.38hot colleagues (lymex et. al.) have done that, but I do not get access to the forum for downloading anything, either. > > But on eevblog, the Datron 4910 reference element has been decrypted completely, as now the content of the Vishay resistor array is known. > Yep, I have to admit, that I also have made much more effort there than here lately. See 'Ultra precision reference LTZ1000'. > > Anyhow, in the 732B manual, there is that circuit block diagram, showing the usual reference amplifier circuitry. > Fluke added some current cancellation circuitry compared to the 732A, and has put all temperature sensitive components inside the oven. > That includes especially the 4-5 precision wirewound resistors around the ref. amp., which cause the most drift over temperature and time. > > I think that's all with 732Bs magic. > > The 732B had two series, one earlier with the SZA263 (Motorola) and after termination of that part, a compatible 2nd source from LT, the LTFLU refence amplifier. > > The mentioned Fluke / Deaver document analyses the different drift behaviour of those two components, but in general, the 732A (based on the SZA263) was less stable, afaik. > > Frank > _______________________________________________ > 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.