Rick, I have two, one I repaired yesterday using parts from the second. Since acquiring both of them about 4yrs ago, I’ve had to repair the “working” unit five times including the first time when I picked it up. Unlike other HP equipment I own, this thing hasn’t been as reliable. Luckily having the parts mule (other than a voltage problem once) I was able to fix it by looking in the repair manual and swapping the impacted card.
As what Tom suggested, I would check the voltages first as the balance of both amplitude and phase is impacted by the +/- voltages being out of balance. I think it was +/- 24V but I could be wrong as I haven’t had a voltage related problem in a couple of years. So far, mine has had 4 defective cards, two bad power supply caps and two bad regulators. Luckily (again) it’s never been that same card. The cards that have failed have had transistor/FET issues opposed to passive components. When I get around to repairing the defective cards I am going to swap out the FETs (on the defective cards) first and suggest you do the same once verifying the voltages are correct and no caps have failed. I’ve had leaky FET issues on 3455A volt meters. I have a card here on my desk for the past year and I’ve gone over the passives two or three times and can’t find a problem so I can only assume at this point that there is a leaky FET on that one. My 4815A is one of my favorite pieces of equipment. It is very versatile. After fixing it yesterday, I tried measuring the impedance of several caps and the unit was accurate to the limit of the meters. I might be able to help you if you get stuck but I’ll admit, my problem diagnosis has been limited to swapping cards after getting close in the manual. Jerry > On Jun 20, 2017, at 1:38 PM, Tom Curlee <tcur...@sbcglobal.net> wrote: > > The first thing I would do is replace all the power supply electrolytic > capacitors on the internal boards. If I remember correctly, the boards are > plugged in and the replacing the capacitors is quite easy. In my unit, at > least one capacitor was shorted and was pulling down a power supply. > > Tom WB6UZZ > > > From: Richard (Rick) Karlquist <rich...@karlquist.com> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Tuesday, June 20, 2017 12:02 PM > Subject: [time-nuts] HP 4815 Vector Impedance Analyzer repair > > I have a non-functional HP 4815, don't know if it > is the probe or the box. A long time ago, there > was a fellow named George Standford (something like > that) who repaired these. My old contact information > for him is no good. Does anyone know if he is still > in business, or if there is any other place that > repairs these things? > > Rick N6RK > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
