HP 3456A DMM or other brand to buy - Page 1
Forum section: electronics / testgear

author: Gmanfro
author_rank: Contributor
timestamp: June 03, 2016, 12:22:10 pm
content: I have a chance to buy a HP 3456a benchtop dmm for $125. It is functioning properly and has just been calibrated within the last year. I understand that this is a large unit, but I do have the room for it. I mainly need it to set mV and low dc voltage on amps for bias, quiescent current, and dc offset. I do need a very accurate dmm. Would this dmm be a good unit or should I look at a different dmm. Portability is not an issue, I have other units for that. It is accuracy I am looking for and a longer digit readout. Also I am on a budget of about $200 max. I do have some other dmm, but seems they are no where near the accuracy of the HP.

author: macboy
author_rank: Super Contributor
timestamp: June 03, 2016, 01:06:24 pm
content: IMHO, A functioning and calibrated 3456A for $125 is a very good deal. I'd jump on it.

author: Vgkid
author_rank: Super Contributor
timestamp: June 03, 2016, 02:01:02 pm
content: At that price with a recent calibration. Go for it, it is a no brainer.

author: guido
author_rank: Regular Contributor
timestamp: June 03, 2016, 10:12:23 pm
content: Agree they are nice meters (got two), but keep in mind that age plays a role. If the original supply caps are still there, you probably need to change them. And they do suffer from 'ROM rot', where the PROMs go bad. Easy fix if you can desolder the old ones and have access to some EPROMS and a programmer. So it might need some work in the near future.

author: Gmanfro
author_rank: Contributor
timestamp: June 03, 2016, 11:39:08 pm
content: Thanks for the info guys!!! Just picked the unit up. Looks in nice shape. He went through it with me, but my head was swimming with the things it could do and what he was showing me. WOW what a large manual that he gave me for it. I guess I have some reading to do. The older gentleman was giving me till today to call him back. Good thing... he had some good offers on it, but promised it to me.guido... yes I have soldering & desoldering units, Hakko, so the fix of caps for me is easy... Are the PROMs available for it, or are there superseded over to a new number? I do not have a programmer for them. If I do need them is there someone I can send them to to be programmed? Will I know when something is going wrong with the PROMs?I do total rebuilds of 70's & 80's amps so redoing boards is easy for me. I do have all the equipment to remove chips also. Guess I like vintage stuff

author: enut11
author_rank: Super Contributor
timestamp: June 04, 2016, 12:33:10 am
content: Hi. I recently purchased an HP3456A and yes it is a monster but I love it! Had some problems as received but help from Forum members helped me solve them. This instrument is a work of art considering its age. If you have any issues later on just search the Forum and you will get lots of hits. Also, lots of documentation available for free on the net which is not something you can say about Asian meters. Once working properly, accuracy and stability are first class, even better than the 34401.enut11

author: orin
author_rank: Frequent Contributor
timestamp: June 04, 2016, 03:04:00 am
content: Quote from: guido on June 03, 2016, 10:12:23 pmI believe it's only a certain range of serial numbers that have this problem.To the OP: what is the serial number?It's a great meter - much better than the 3455A which it sort of replaced. I still like the 3455A's display better though.

author: Gmanfro
author_rank: Contributor
timestamp: June 04, 2016, 10:08:00 am
content: It is a series 2201A. Guess I lucked out and got the better seriesAfter doing some internet searching last night I did find the same thing as you as far as the problem with the PROMs... Seems like it's more prone to 2015A serial numbers. I also noticed that the 2015A are the units with the fan & air filter on the back.2201A has the fan & filter removed and the power regulator is in place of it on the back exposed. (TO3 case)Seems like all series suffer from bad capacitors in the power supply.... but that is expected in older equipment... they just start to dry up... plenty of experience with bad caps in older amps, that is why I do total rebuilds.Also one other tid bit I see is that 2512A series my have started with the soft switches instead of hard switches... Interesting research article by Marvin Gozum

author: guido
author_rank: Regular Contributor
timestamp: June 04, 2016, 11:29:30 pm
content: ROM images are available. What i noticed was that the instrument freezed up when selecting a specific button (jumping to bad code in one of the ROMs). The failure depends on what part of the code is bad. E.g. if it is at the part for the initialisation, the instrument would freeze at power on.I replaced the three PROMs with six EPROMs, just because i had those available (2532 if i remember correctly). With some bodge work you can put one 32k ROM inside.

author: enut11
author_rank: Super Contributor
timestamp: June 06, 2016, 11:09:20 pm
content: Quote from: Gmanfro on June 03, 2016, 11:39:08 pmA nice little 3456A quick reference guide can be found athttp://www.ko4bb.com/getsimple/index.php?id=manuals. It is the 6Mb file.enut11