No.104 - 3rd HP 34401A 6.5 digit Multimeter Repair 

Nice fix Ian. I'm sure the videos don't always reflect the time and effort you put in to these repairs.

I have one of these meters, had to fix a problem with the AC power switch... Nice to see you working on the guts of her... I guess I should be looking at to get the service manual...this meter has a nice bit of history; it has asset number 0001 on it, from the main R&D site of a mobile device company in Finland...so, maybe one of the first instruments purchased for the engineering team!

That was one crispy critter Tant. Nice job Ian.

Oh, wow, a cool and interesting repair video... we're supposed to be what... surprised by this? Oh, how SHOCKING, this has NEVER happened before... Ha ha ha... Seriously, thanks for making these, Ian, I really appreciate it.

Still using one almost every day in our testlab.

Feedbackloop has a channel where he fixes a display that had some bad tantalums and bad inductors on the the display board. The display was brought back to a nice brightness. I believe it was video #20. Thanks for all the great videos.

Nice fix !...cheers.

That was a nice and easy repair, I wish they were all like that lol!

Nice repair. I also got one of these old ones, from about 1993, or so, it's my go-to-guy, still fine. Maybe I also should check the capacitors some time.

Well done Ian 😃

Jolly good fix, for a windy Scotland🙂

First time I have seen diagram analysis where all involved components had no connections drawn :-D

As a starting out person, I keep looking for these, and I can never find one that's affordable... Well there was one, but it had fire damage. lol

Thank you for the video!

Very nice work! Keep up Ian!

Excellent job Ian =D

e621 😧

i hope one day to afford a 2nd 34401a, so that i may check it against my existing one and only beloved. which is my daily workhorse for pretty much everything. the thing with my unit is its vfd is like this one, currently good but with the unobtainium driver ic. so the day will likely come to replace with the oled project. at which point i will need to cross check that the oled display mod. to be certain that it is not going to throw off the metter of affect the accuracy or whatever. i hope it doesn't but nobody seems to know yet (at least not for certain, we suspect it should be ok)

Thanks for sharing, I really enjoy the videos. One of my 34401A had a bad unobtanium relay. The best replacement is only good for 200V instead of 1000V. Not a big deal for my use case. These are great DMMs. Since the tantalums in these devices tend to fail at some point, would you consider replacing all tantalums or wait until they fail?

1.2345 Volts...reminds me that I must change the combination on my luggage.

Auch, hot air on precision instruments :( . You can see poor film capacitor bubbling and melting next to tant.... Tantalum caps easily removed with soldering iron without stressing everything off. All blacked FR4 need to be removed too, not left there to cause huge leakage.

As a wise man once said, "It's always the capacitor."