David, that instrument on ebay is definitely from the agilent area, i.e. built after 2000. It is really ok, and does not need any repair. Obviously, this AC range is a bit outside calibration @ 3V, 4MHz, but that is normal after some years w/o adjustment, and not a defect at all. Probably you know the different kinds of calibration at HPAK, obviously they chose the cal w/o adjustment option. Currently, the KS server is down, otherwise one could download the full calibration document, and check that, also the date of manufacturing . If you'd ever need these high frequency measurements, it's possible to do that by means of an appropriate signal generator and a thermocouple. The internal LTZ1000A circuit might stabilize with age, also the internal 40k VHP100 reference resistor might get better. The annual drift of the LTZ circuit is nominally 8ppm, but that is not fully specified. In theory, that applies only if the instrument is powered on continuosly. If it's switched off most of the time, the LTZ chip should not age at all, but it may show hysteresis (see AN-18, first item) So to my opinion, in this case it makes no difference, if you have an older or a younger instrument. The rest of the circuit is either (short term) stable, or not, also mostly independant from vintage. Due to the regular AutoCal process, this is of no real concern, as all these other drifts will be cancelled by the machine. The only component which determines the short term stability, is the ADC ASIC. It might have a good T.C., from zero to max. 0.5ppm/°C, and it might have a low timely drift in its calibration parameter CAL? 72. If latter is not the case, as described in AN-18, 2nd item, you really have a monetary problem. But in any case, this stability risk is the same for every vintage of instruments. Anyhow, I would prefer a newer unit like this one, as some other components degenerate over time, like the un-obtainium fast comparators. In the end, this instrument is not cheap, especially w/o proper adjustment. 3000$/€ would be a more reasonable price. Frank

But the seller told me he had been quoted 2100 Euros for repair, so I assume Keysight thought it needs repair, not just adjustment. Also, as far as I know, all Keysight calibration do include adjustments. I'd like one, but don't really have the money, but I thought the price excessive. Dave Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT, United Kingdom Registered in England and Wales as company number 08914892 http://www.kirkbymicrowave.co.uk/ Tel 01621'680100 / +44 1621-680100 On 16 January 2018 at 16:46, Dr. Frank <frank.stellmach@freenet.de> wrote: > David, > > that instrument on ebay is definitely from the agilent area, i.e. built > after 2000. > > It is really ok, and does not need any repair. > > Obviously, this AC range is a bit outside calibration @ 3V, 4MHz, but that > is normal after some years w/o adjustment, and not a defect at all. > Probably you know the different kinds of calibration at HPAK, obviously > they chose the cal w/o adjustment option. > > Currently, the KS server is down, otherwise one could download the full > calibration document, and check that, also the date of manufacturing . > > If you'd ever need these high frequency measurements, it's possible to do > that by means of an appropriate signal generator and a thermocouple. > > The internal LTZ1000A circuit might stabilize with age, also the internal > 40k VHP100 reference resistor might get better. > > The annual drift of the LTZ circuit is nominally 8ppm, but that is not > fully specified. > In theory, that applies only if the instrument is powered on continuosly. > If it's switched off most of the time, the LTZ chip should not age at all, > but it may show hysteresis (see AN-18, first item) > > So to my opinion, in this case it makes no difference, if you have an > older or a younger instrument. > > The rest of the circuit is either (short term) stable, or not, also mostly > independant from vintage. > Due to the regular AutoCal process, this is of no real concern, as all > these other drifts will be cancelled by the machine. > > The only component which determines the short term stability, is the ADC > ASIC. > > It might have a good T.C., from zero to max. 0.5ppm/°C, and it might have > a low timely drift in its calibration parameter CAL? 72. > > If latter is not the case, as described in AN-18, 2nd item, you really > have a monetary problem. > > But in any case, this stability risk is the same for every vintage of > instruments. > > Anyhow, I would prefer a newer unit like this one, as some other > components degenerate over time, like the un-obtainium fast comparators. > > In the end, this instrument is not cheap, especially w/o proper > adjustment. 3000$/€ would be a more reasonable price. > > Frank > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/volt-nuts > and follow the instructions there. >