Agilent 34401A Troubleshooting & Repairing Multiple Errors

I purchased this unit on Ebay knowing it was failing the self-test and had the following errors: 612, 613, 615, 617, 618, 619, and 621. A quick search on the internet led me to this ‪@EEVblog‬ forum thread: www.eevblog.com/forum/repair/...
After changing out some electrolytic capacitors I swapped out chip U201 - not an easy task without SMD tooling. I found this video from ‪@ToltecMerc‬ very helpful: • #2 Repair of Agilent 3...
The chip did the trick and the unit now passes all self-tests.
Timestamps:
00:00 Introduction, self-test errors
01:55 eevblog forum thread
02:40 Schematic analysis
04:00 Capacitor ESR results
04:48 18V rails fix themselves
05:30 Chip replacement strategy
06:09 A new strategy
09:07 Self-test passes, resistance checks, super stoked

[@tekfreak6128]

Nice repair and a satisfying result. In the days when hot air guns were exotic, you could use a fine tipped pair of side cutters to remove these chips. Another thing to always check are the smd 3.3v zener diodes- a common failure point. Thank you for sharing.

[@TheDefpom]

Nicely organised video, just a suggestion for soldering those kinds of chips, get some Amtech NC-559 tacky flux it will make the joints so much nicer.

[@andymouse]

Squeak !

[@InssiAjaton]

Nowadays there is a great way of doing calibration on your own bench - just get one, or preferably two of the reference boards built around an Analog Devices chip.. They give you nominally 2.5, 5, 7.5 and 10 V with an 8 digit factory calibration document. I bought two of them and compared them. Nearly perfect! Then I checked my Agilent 34411, 6-1/2 digit meter. Perfect agreement 3-ways within my Agilen resolution. I have forgotten the price of those references, but the two of them together were well below your stated outside service quote. Of course, you still need your 15 V DC bench supply.

[@andymouse]

Nice result !...cheers.

[@jessicav2031]

You need hot air! Get an 858D, they are only $40. You don't need the $300 fancy stations, the $40 one is good enough if you're on a budget 😀

[@offkafka]

Thanks for the recommendation!

[@derkarhu5079]

I saw a guy using a piece of 12 or 14 ga. Wire, tin it, cut to the length of the 4 pins, lay it on the pins, on both sides, hit it with a bit more solder, and it acts as a big soldering tip, off comes the device.

[@mosfet500]

You really need decent equipment to unsolder ships, eight pins are relatively easy but once you start getting to the 32 pin tiny things get hairy fast and you don't want to ruin your pcbs.
I have the 34401A, it's my favorite meter for everyday stuff. I have the 34465A which is more versatile and better for histograms a things like that but the 34401A comes right on with no delay so it really saves time, probably the best known meter made.

[@offkafka]

You are not wrong. This was definitely a risky soldering method, but it worked out in the end. I won't say some amount of luck wasn't involved!

[@lohikarhu734]

i saw a nice trick to heat all the leads, at least on one side...use a fat piece of copper bus wire, looped around that ic, and apply solder liberally, then use tweezers to pick up the ic, and wire, at one time...tried it on a 10-pin connector, worked a charm...

[@derkarhu5079]

As I said, before I saw your post...

[@Radiotechnik]

Nice precision multimeter. You make interesting videos. I leave a subscription and a thumbs up. Regards.😀

[@vaniz2012]

asli keren

[@TheSoundtec]

buy an desoldering gun..!

[@offkafka]

I know, it's on the list!

[@treadmillrepair754]

HP, Agilent or Keysight whatever you want to say are low quality products.
Fail often.
1000 times better quality Keithtly, Fluke and others.