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You can get the clip from Artekmedia. The first step is always to check all the low voltage power supply voltages. The calibration on the 3458a just needs a precision 10 volt reference and an accurate 10 k resistor. It is a wondeful instrument but repair and cal Keysight is a bit painful. It is still in production.

Regards and good luck.

?

I am trying to restore an HP3458A DVM and I need a little help.

I acquired this unit on ePay some time ago and I finally found some time to check it out. The outside and inside are both neat and clean. The build date is 1988, but someone has maintained over the years, because it has the latest firmware ROMs fitted (Rev 9). The Dallas NV RAMs are 2012, so they are nearing end of life. It is fitted with Option 002? Improved DC reference stability 4 ppm/year(!). The Cal sticker says it was last calibrated in 2013.

A visual check of the PCBs revealed nothing obvious, so after setting the mains switch to 230V I decided to power it up. I was greeted with a sizzle and an acrid smell. I have been there before with other old test gear - the Schaffner mains filter kacked itself. So I ordered a new one and replaced it.

When I powered the unit on again, I was greeted with a short BEEP and the first rectangular block of the green electroluminescent display flashes ON and OFF. That's as far as it gets. I have searched the Agilent manuals, all the info I could find on the internet and watched some excellent Youtube clips on repairing and calibrating 3458A's. I cannot find any troubleshooting reference for a flashing single character block on the display.

I am thinking there may be something wrong with the firmware code in one of the EPROMs that is causing it to hang while booting. I have an EPROM reader/burner, but I am reluctant to go there until I am sure I have to. I would be most grateful for any advice anyone may care to offer.

Cheers,
George