HP 3480A / 3484A repair/restoration

[Nevada]

Hello,

I recently acquired a nice HP 3480A multimeter from the (original) Nixie-era with a 3484A module. Unfortunately the seller disassemled the module earlier, and he removed the option cards. I re-installed them (although the screws are missing), but there are five wires which I don't know where should I connect. I didn't find any information about that in the service manual.

Could somebody help me?

[factory]

If you haven't already downloaded it a manual covering the later revision boards in your 3484A can be found on the Keysight website under 3480D 3484A and older first edition is on hparchive.

The only one that is obvious is the green wire from the top board in the picture (A6 ohms/DC convertor) should go to the Ω connection on the lower board (A1 attenuator).

Is the orange wire is from the AC board (A7)

I guess you need to identify the components on the middle board (A2 DC amplifier) that the wires are connected to and trace through the diagrams to see if you can work out where they should go. The three wires are shown between the A1 & A2 circuits as the color codes; red (2), black (0, low current ground) and green (5, filter amp output).

David

[Nevada]

David,

Thanks for your suggestions! Finally I could made them working, but unfortunately it turned out, that somebody killed its most interesting part: the 10MHz RMS converter...
Although the basic function (DC voltage) works ok.

[factory]

Never noticed before that the RMS converter (11153A) option was covered by a separate manual, luckily hparchive have it.

That part is the thermocouple, guess finding a replacement would be impossible, as most 3484A plug-ins didn't have the AC or ohms options.
This seller has destroyed a 3484A with all options. https://www.ebay.com/itm/293079335436

I'm now looking for a 3484A for my 3480B, it has a 3481A buffer plug-in, this one seems to very uncommon, can't even find a manual for it, either free or paid for.

David

[doktor pyta]

sounds familiar
https://www.eevblog.com/forum/testgear/hp3403c-marvels-(photos)/msg3349034/#msg3349034

[factory]

That does look similar, wonder what the differences are? as they have different part numbers.
The digital panel voltmeter for the 3404x was used for other HP test gear too, or sold on it's own as the 3431x.

David