I've also seen excessive Guard to Low leakage when varistor RV501 has gone bad (it's located on the front/rear switch pcb and it's possible to replace it while leaving the circuit board in place if you are careful). HP/Agilent/Keysight Part number is 0837-0196, cross referenced to a Harris Corp. V430MA3A.
On Fri, Aug 15, 2014 at 10:46 AM, Stephen Grady <grady.st...@gmail.com> wrote: > Randy, > > I have come across a few 3458A's that had leakage between Guard and Low > when > te guard is in external guard position. This was due to a leaky external > guard switch and/or leaky front rear switch. This can be quickly determined > by measuring resistance between guard and low with guard external. This > normally in not an issue except when you are using 3458A to measure voltage > with low above earth potential say in a bridge the guard low leakage will > be > loading other arm of the bridge. > > Kind Regards, > > Steve Grady > Sydney, Australia > > -----Original Message----- > From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On > Behalf Of Randy Evans > Sent: Friday, 15 August 2014 1:22 PM > To: volt-nuts@febo.com > Subject: [volt-nuts] New HP3458A > > I picked up a used HP3458A today, which I needed for some precision DC > measurements i need to make. It passes all the self tests and the Auto Cal > but is there any thing else I can check ( I have a 14 day RR). It reads a > 10V standard I made within a few tens of ppm, but it's not a 732A but that > is at least comforting. It also reads an ESI 10Kohm standard resistor dead > on. > > The only problem is that the display has some faint pixels in some > locations, with three in the second row for every digit location dead. > Likely a pixel driver I would think. > > I am not too familiar with it yet but I noticed when I push the auto zero > button, the display has a blinking square until I hit a measurement mode > button; e.g., DCV, ACV, OHM, etc. Is this normal? > > Regards, > > Randy Evans > _______________________________________________ > 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. > > > --- > This email is free from viruses and malware because avast! Antivirus > protection is active. > http://www.avast.com > > _______________________________________________ > 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.