We managed to snatch an old(1983 going by chip date codes) HP 3456A 6.5 digit DMM off ebay recently.
It arrived quickly and well packed from Italy but when I turned it on I was greeted by a display showing 6 dashes instead of a measurement. So I went through the manual to see if I’m being an idiot and don’t know how to use it but it seems like the old beast really did have a problem…
Going through the troubleshooting sections of the manual I learned that if you are presented with the dashes on the display and you run the self test and you DON’T get error -3 then you have to check pin 9 of U17 on board A3 and pin 10 of U13 on board A4…So I opened it up, checked those chips and what do you know? Some cold solder joints on U17. 5 minutes and a bit of solder later and it was back in action!
Check out the photos – I have to say this multimeter is a thing of beauty. It is a truly beautiful design both electronically and mechanically!