Yokogawa multimeter repair

[Parak]

I've recently acquired what seemed to be a decent condition Yokogawa 73401, and the immediate thing that I noticed is that the amp and temperature range at the beginning of the selector dial are displayed as (non-working) ac and dc mV/V ranges. All functions after that (cap, ohms, continuity, actual mV/V ranges) work perfectly. It's almost like the selector dial is not working properly, but after removing it, I don't see anything that might be out of the norm.

When I took it apart, there was a fair amount of leaked battery fallout from a previous incident, that sent the acid all the way up to the pcb as well (bleh). It doesn't seem that any traces were affected after a quick continuity check, but there's a few that seem to have exposed copper as result.

Anyway, posting this in hopes that someone has ever seen something similar even with other multimeter brands. In the meantime, I'll see if I can have Yokogawa dig up a service manual for me..

Thoughts are much appreciated!

[retiredcaps]

When I took it apart, there was a fair amount of leaked battery fallout from a previous incident, that sent the acid all the way up to the pcb as well (bleh).

I suggest giving the pcb and range switch a complete IPA clean and scrub.  The following repair is somewhat related and may give you some clues?

http://mrmodemhead.com/blog/fluke-23-iii-dmm-repair/

[Parak]

I suggest giving the pcb and range switch a complete IPA clean and scrub.  The following repair is somewhat related and may give you some clues?

http://mrmodemhead.com/blog/fluke-23-iii-dmm-repair/

Excellent, that's pretty much the same kind of issue that I have, except the corrosion is quite far away from the selector switch and is nowhere as major. Time to do more continuity checks, it seems.

Thanks!

[retiredcaps]

I forgot to ask you to post some teardown pictures of your meter.  After all, it is eevblog here!

PS. Don't forget the IPA bath/clean.

[zaoka]

Can you post few pictures from inside?

[Parak]

Righto, pictures. Still looking for the fault, but it's getting cleaner at least. Has a bunch of flux residue too which needs to be cleaned better. Desoldered the battery holder as that area needs more cleaning, and I need to get a new one anyway as it's all cracked and corroded. I'll have to take a picture of the selector switch underside too, but it's basically just spring contacts on the bottom of that plastic cover.








Some of the things not shown: The pcb is held inside the bottom cover by one small screw under the left fuse. The top case has a lockout feature for the amp inputs when not on the amps ranges. The inputs have a felt washer on the bottom (around) of them for protection/dampening; removed for cleaning.

[fluxcapacitor]

i can see some corosion on a resistor.