Before buying, Agilent 34401A reads high issue.  What are the possible causes? - Page 1
Forum section: electronics / repair

author: StrayElectrons
author_rank: Contributor
timestamp: January 08, 2025, 03:24:08 pm
content: This 34401A multimeter has issues. For example seller said voltage reads 21V for measured of 9V and other functions are incorrect.Seller is asking 358.29 canadian dollars, shipping not included, which is shipping of 15 dollars.What are the possible causes other than calibration to do, which I can do. I don't mind repairing as long as proprietary parts are not damaged.Cheers,

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 08, 2025, 03:32:42 pm
content: Hello,I've never before heard about such an odd error on the 34401A.Please give a complete and precise description of all the errors this unit shows.Otherwise, it's not possible to make any educated guess about the possible problem(s).Frank

author: StrayElectrons
author_rank: Contributor
timestamp: January 08, 2025, 04:01:43 pm
content: Thank you, I just sent asking seller's for more information about this issues.This is all I get from the auction text, fyi.I kept coming back to the 34401A multimeter as good choice after reviewing several chinese made bench meters posted by others via google search on each model with forums included. I kept finding the cons which considered to be biggie for me. Owon models I read about is not too bad but long start up is not a problem as long as other cons that are not a issues to me unless your replies states otherwise.And I don't mind repairing as long as initial purchase does not explode my budget on initial purchase of a meter that needs repairs or not. Older meters made by HP and other older meters, does not have diode tester which 34401A does. This is important item as I use this the most. I also do voltage readings. I know this diode mode is custom programming with low voltage and limited current while meter reads this as voltage for voltage drop across diode and transistor junctions. I could made a presdo diode tester made with external box sourcing current limited to 5mA at about 3V to 5V with multimeter set to voltage across the DUT n-p junctionsI know people would suggest handheld meters but I don't want this, already have two, have to reposition all the time and keep tipping over and hungry for 9V batteries. While bench meter is perfect solution and out of way working on electronics.Cheers,

author: Swake
author_rank: Frequent Contributor
timestamp: January 08, 2025, 08:47:38 pm
content: Patience. You will end up finding something that sweets you.360 CAD for a broken box is a lot of money. Certainly when it is a weird issue and you don't have experience nor parts to solve this.

author: bdunham7
author_rank: Super Contributor
timestamp: January 08, 2025, 09:05:15 pm
content: That's too much for a unit that may have a difficult to repair issue--and yes, proprietary parts may be involved an it is definitely not a calibration issue. It is a later model, US made, Agilent version, so that is a plus, but broken, no bumpers/handle. $250US is just too much IMO. I recently posted an auction (in France, unfortunately for you and me) of NEW old stock 34401As for $400US. Those got snapped up (50 of them!) If you look at sold units on eBay, you'll find a pretty nice one went for $350US and a broken one with what is likely an easier fix went for $150.If you are on a tight budget and you want a simpler meter but with diode testing, the Fluke 8840A/8842A series has a "hidden" diode mode that is actually documented but not on the front panel. You simply select the 2K resistance mode, the test current is 1mA and the reading in k-ohms is your forward voltage. It works up to 2V. You can probably find a working model with AC (AC was optional, make sure you get it) for what you're going to pay for the broken 34401A. Of course the 34401A is more advanced, has serial comms and menus full of slightly more advanced features (the 8840 series doesn't even have min/max or a beeper...) but if you want one, get a decent one.

author: StrayElectrons
author_rank: Contributor
timestamp: January 08, 2025, 10:57:55 pm
content: Yes, I saw your knock-out lucky once in a lifetime for a new meter on your auction earlier on and was not ready due to other commitments. Now I have sufficient funds.Ironically, even the Siglent had and still have teething issues too on older postings about these. Now too high cost at 1,000 for a chinese quality. No thanks.I have already eventually came to conclusion that any chinese models is not worth looking at, excepting Siglent which is better than average but still. I have already researched all the current selling bench top meter models listed on aliexpress.I know from experience with broken stuff, *especially* from Ebay, is boat-load of uncertainties and lottery is high chances that has been looked at then tossed on the auctions and sellers didn't want to respond to my questions. Also Ebay does not include all the results if I used lab or bench multimeter as search string because search mechanism which was remade poorly, old one was massive like 1,000 results, not anymore. If I use specific models I get lot more results but it is very tedious to find all the models and use them in the search one by one and still miss some good deals for decent bench multimeters.I tend to buy fix-uppers for reasonable price and buy parts once in awhile and fix them works well for me due to limited monthly budget and for the fun.Cheers,

author: J-R
author_rank: Super Contributor
timestamp: January 09, 2025, 04:50:30 am
content: Shouldn't your best DMM be calibrated?I like the 34401A well enough and those new old stock units were a nice find perhaps, but overall the deal was somewhat overrated. No calibration since manufacture in 2014, and in daily use the 34401A is just very clunky to operate compared modern DMMs.https://www.ebay.com/itm/355801306161https://www.ebay.com/itm/234687610434(https://www.equiptek.com)

author: Swake
author_rank: Frequent Contributor
timestamp: January 09, 2025, 09:14:05 am
content: Calibration requirement depends on your use case. The first thing is that you must be able to trust what your DMM tells you.Should you really have the need of those many digits precision then you always arrange for the calibration yourself with a reputable lab.About the 2 links provided, its a very good example of what not to buy. I would not want them anywhere near one of my multimeters, and certainly not for any sort of calibration.- 'Bright display' and provides pictures in taken low light conditions.- Pictures of at least 2 different DMM in the add (logo is scratched and then not, different buttons)- Not showing serial number and bluntly mentioning you'll get another one than the one in the pictures.- Excellent physical condition: pictures show dents, scratches and dirt everywhere.- Calibrated: The voltage standard says calibration due in 9/3/98.- Calibration certificate shown is a joke. It is a photocopy. It does not even contain the serial number of a tested device... Call equipment cannot be traced to origin reference.Be careful with what you buy and from whom you buy it from.

author: J-R
author_rank: Super Contributor
timestamp: January 09, 2025, 11:00:33 am
content: Most of those concerns are aspects of having multiple quantities for sale under one listing. It's also common for some sellers to be a bit less-slick on the presentation side. Just ask for photos of the specific unit they plan to send. If you don't like what you see, you can ask for a different one.Global Test Equipment has a 9500+ rating and a 20+ year old eBay account. They offer NIST calibrations:https://4gte.com/services/test-equipment-calibration/I've dealt with Equiptek in the past. I was going to purchase a 34470A and asked them to send me more photos and the calibration printout, which they promptly did.They have two eBay accounts, both have excellent ratings and are over 20 years old:https://www.ebay.com/usr/equiptek_labs_inc_650-261-1711?_tab=abouthttps://www.ebay.com/usr/call.electrojazz.650-261-1711?_tab=about

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2025, 11:59:23 am
content: Quote from: StrayElectrons on January 08, 2025, 03:24:08 pmschematics exists ask the seller to do the self tests routine and see the errors codes, if any pop's up, if the seller dont want ..... move awayyou can or could have input parts problems, burned protection parts, coto relay, front rear switch problems, some could be easy to fix some not,but 1st ask the self tests resultsoh and do completely read the seller conditions etc... if he wrote sold as is, and he shows the problems in pictures it means you have to live with your choice, no refunds

author: StrayElectrons
author_rank: Contributor
timestamp: January 09, 2025, 03:14:12 pm
content: This seller responded by accepting my offer of 200 USD, was 260 USD. and gave me more explanation of the issues. The key word is no errors which is good news. Just bought the 34401A. This was my first ever expensive purchase in over 30 years of online purchases.I know there is schematic for this 34401A so I'll go and get it once I get home.I tried other sellers, one didn't responded, and there was another Japanese seller who is not very fore-coming with details and declined the offers.Cheers,

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2025, 04:05:30 pm
content: hope it goes well, vfd no too dimand its physically clean, non broken handle etc ...as to re-certify them, Montreal city and Quebec city you have cal facilities, was around 160 200$ ?

author: StrayElectrons
author_rank: Contributor
timestamp: January 09, 2025, 11:22:54 pm
content: Seller finally answered my last question about this VFD condition. Anyway: Cabinet, buttons and front & back end is mint and VFD is like new, very bright and crisp. Red and black jacks, square buttons. I'm aware of the VFD aging.Only thing I don't have is handle. Chinese sellers have the rubber bumpers ends and handle kit.Is there a screws fixing to keep handle on, or just twist to locking positions?Cheers,

author: NE666
author_rank: Frequent Contributor
timestamp: January 10, 2025, 09:11:51 am
content: Quote from: StrayElectrons on January 09, 2025, 11:22:54 pmNo, the latter. The handle molding is slightly sprung, to hold it in place when located.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 10, 2025, 11:45:09 am
content: no screws, just need to be careful while stretching the handle locks into place,do it slowly

author: StrayElectrons
author_rank: Contributor
timestamp: January 10, 2025, 03:31:24 pm
content: Thank you, I know what you meant, I had used test instruments before and the type of handles. Was new to this model.Cheers,