No.085 - ***Another*** HP 34401A 6.5 digit Multimeter Repair - Part 2
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- Опубліковано 5 вер 2024
- After acquiring another faulty HP 34401A Multimeter and making some repairs in Part 1, in this Part 2 video I make further repairs and try to get the main processor up & running.
Update: Here's the 34401A with the a new VFD fitted and a bit of a clean up.
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Part 1:
• No.084 - ***Another***...
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Update: Here's the 34401A with a new VFD fitted and a bit of a clean up. This new VFD was clearly 2nd hand (Ebay) but it's really nice and bright and better than the 1st 34401A I repaired! I think this 34401A will be the one I sell.
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Those static rams usually I suspect when see reset line being pulse. Had to replace way to many over the years. Love old HP gear but definitely problematic. Usually line filter, Rifa X/y capacitor, tantalums, DAC’s and static rams usually a issue with HP gear from this area. I lost count?
Once repaired HP gear is pretty reliable.
I had a feeling this would be fixed by the end of this video. Always nice to see test gear brought back to life.
I'm not really a fan of more than 2 or 3 parts to a repair.... try to avoid most of the time. This one came quick hence the short part 2.
SRAM eh, I will have to remember that one, another nice meter for the collection
Hi Ian, another great repair. I work on routers and switches, repairing and testing. The number of switches I get in with failed static RAM is very high. They seem to last about 6 or 7 years before failure. They are usually the 46Vxxx series in a TSSOP 66 pin package.
Odd the later ones do two beeps on startup. These as I may have said before are super stable and reliable. Hold down any button and power on for a full power on test. Thank Ian.
It passes self test no probs.
nice work Ian!
Nice job!
Yeah, this one had multiple faults, some of them caused by these old caps. Interesting and great repair video series! 👍
Great. I bought a used 34401A, an Agilent one, about 22 years old, where the front panel fell to pieces when I took it off. They had left out the front latch, because there were nothing to attach it to. Consequently the front input assembly flexed when you inserted cables, so I was worried the board could have been damaged. Everything is fixed now, with a new used front panel from China and new bumpers. The PCB was surprisingly dirty and the rear connectors quite a bit oxidized. Seems to work fine after a cleanup.
Fantastic repair Ian =D
Great repair ! Awesome.
I would rock that display, no problem. Nice job on this repair.
great repair 👍
Hi Ian, good vid mate. You are aware that if you increase the voltage rating of the caps you are reducing the value? High value caps are only the stated value near their working voltage, so changing those to 35 volt has probably reduced their value by at least a third in circuit.
Ian, ingenious repair. Chapeau.
Nice job. My display seems to be hanging on ok and meter works fine. Just got a 512mhz frequency counter that does not reset everytime to fix, and 512mhz signal generator that refuses to output the same frequency as the display. So a few jobs to do. Just need to find some silver loaded lead solder for the sig gen as it warns against using normall solder.
Great work !...cheers.
Great a part II video nice🙂Ian well done
Squeak !!
@@andymouse Crowdie Cheese!!!!!!!!!! go watch and like my unable maker videos🙂
I wouldn't mind buying a used 34401a, prices on eBay are insane though 😢
Ian, I'm supposed to be working right now... can you stop uploading videos during my workday? 😁 Awesome repair.
Just tell your boss it's necessary research......LOL
Where can you find the schematics of these old meters. I have one that the amps ac is screwed up. You are motivational in encouraging me to look into repairing the meter.
ASIC just means "application-specific integrated circuit", so I would think that would cover gate array and standard cell IC's, and of course, full-custom chips.
Thanks Sir ,Very helpful technical support and very keen trouble shutting process, Sir I need Your help regarding the same DMM, My one kept unrepair as the power transformer primary winding burnt, and it is not available here, can you send me the details of secondary winding, the all ac voltages, hope you will consider my request thanks again, have a good day
Hi,
I dont have the voltages to hand, however you can work out the windings required by looking at the DC voltages required and calculating back to the transformer windings.
I am not sure the transformer is the same spec as other DMMs, i woukd doubt it though.
Update: There are 34401A transformers available on Ebay.
Hi Ian,
I also own an Agilent 34401a. I replaced all electrolytics and tantalums, all works great but the AC current bellow 10 ma AC, can you run some tests on yours to compare results. It was the same before replacing the caps and re-calibrating the 10 ma AC as per the calibration procedure. I posted this on another channel but haven't gotten a replay. Any help would be appreciated.
Thank you.
Nice video. I did change display also..and results were so amazing..display was just like new...then i changed it on second meter and results were not so good so i bought another one..and changed that one and results were better...but never so good as on the first one..but it looks ok like 3 years used..so almost as new..too bad i didn't order from same seller ..haha if i knew that i would order it next time as well..anyway two 34401A are just fine..no need to have more..i need to get one 7.5 digit..but those cost a lot more..i got 2001 but i'm not happy with noise..maybe i will try 2010 next time or 2002 ..but prices must go down and not up..lol...Anyway as always nice video..
Probably not the problem, but I remember someone in a vid years ago had a bad resistor in the display that made it dim.
Some of those metcal tweezers would help desoldering these parts 😉
......so they would! 😏
How do you go abt testing the gpib/hpib port?
In Part 3, Ian discusses the global shortage of HP 34401A Multimeters...😉
Nah!......Ian discusses how to save 34401A DMMs from landfill....😁
@@IanScottJohnston Point! 😀
brilliant :-)