Agilent U1272A missing contact - rotary switch - Page 1
Forum section: electronics / repair

author: vahelduvool
author_rank: Newbie
timestamp: November 29, 2015, 11:50:40 am
content: Hi!I have Agilent U1272A multimeter - worked so when rotary switch started to switch off multimeter. Problem was when I measure VAC then I move to ohms and it restarted. I take it apart and clean the contacts with pencil eraser, bolw some air on it and put it back together. Now it´s not working. Problem was that I clean it with compressed air - thers one contact missing.Is there some way to get that contact. If not then this multimeter is for spare parts or for Dave.Thank you Dave for teardown.

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 29, 2015, 12:04:29 pm
content: Have you tried searching everywhere for it?If all else fails, you could probably salvage one from a cheap multimeter or something...

author: Muttley Snickers
author_rank: Unknown
timestamp: November 29, 2015, 01:53:14 pm
content: I have a couple of these meters and they have been in regular use since they were first released or not long after Daves first video on them, other than the initial firmware being problematic and upgraded these meters have never once given us any problems.As these meters are IP54 rated for dust and water resistance I suspect that the meter would have been rather clean inside when you opened it up unless your work environment is subject to very fine particulate matter, if it was a faulty selector switch causing the problem then this is the first one that I have heard of unless you were running an early version firmware in which case these meters would behave erratically.I think your options are to either find the lost contact or get in touch with your local Keysight service department and see if they have a replacement part otherwise and better still send the meter in for repair, and finally if you have the sufficient tooling and skill then you could perhaps make one but finding a metal strip with the same electrical and mechanical properties as the original may be a challenge.Best of luckMuttley

author: wraper
author_rank: Unknown
timestamp: November 29, 2015, 02:49:04 pm
content: Quote from: vahelduvool on November 29, 2015, 11:50:40 amI just hate when receive equipment after this procedure. What a "smart" idea to scrape off the gold plating from the pads and leave a layer of residue from the eraser instead. BTW probably you needed to just upgrade the firmware, with some old firmware version U1272A could catch a glitch when switching the ranges. Even if not the firmware issue, all you needed was to just clean the pads with alcohol or some other solvent. You can order the top case assembly which should come with a switch, but ask them first to be sure.http://www.keysight.com/my/faces/partDetail.jspx?lc=eng&cc=GB&partNumber=U1272-64401&imageStatus=NO&NEWCCLC=EEeng&_afrLoop=66484176282000&_afrWindowMode=0&_afrWindowId=12ys91c43j_19#%40%3F_afrWindowId%3D12ys91c43j_19%26_afrLoop%3D66484176282000%26imageStatus%3DNO%26lc%3DEE%26cc%3Deng%26_afrWindowMode%3D0%26partNumber%3DU1272-64401%26_adf.ctrl-state%3D12ys91c43j_31should cost about EUR 30, they most likely will forward you to your local distributor.

author: AF6LJ
author_rank: Unknown
timestamp: November 29, 2015, 03:54:59 pm
content: A pencil eraser is a bad idea, leaves sulphur compounds on the board not to mention any oil and dirt that eraser has in its pours.Besides if it looks clean; Don't Clean it.

author: tooki
author_rank: Super Contributor
timestamp: November 29, 2015, 07:17:57 pm
content: Given that most erasers are now made of synthetic rubber or plastic, I doubt sulphur is a serious problem. (And plastic erasers normally contain no grit, so you're not likely to cause much mechanical damage to the plating.)

author: wraper
author_rank: Unknown
timestamp: November 29, 2015, 07:20:52 pm
content: Quote from: tooki on November 29, 2015, 07:17:57 pmSomehow every time I see the pads after them, they have the most of the gold plating gone.

author: AF6LJ
author_rank: Unknown
timestamp: November 29, 2015, 07:43:31 pm
content: Quote from: tooki on November 29, 2015, 07:17:57 pmThose switch tracks should not be cleaned with anything of the sort, use a soft lint free cloth or a paper towel soaked in IPA or a similar solvent.Regardless of what it is made of an eraser that is designed to remove pencil graphite from a piece of paper is abrasive.

author: tooki
author_rank: Super Contributor
timestamp: November 29, 2015, 11:07:25 pm
content: While I agree that pencil erasers are not the appropriate cleaning product for gold pads, your blanket statement that all pencil erasers are abrasive is just nonsense. Pencil erasers work by binding the graphite particles, which are not bonded to the paper. (Remember, the first product used to erase graphite was bread.) My understanding is that natural rubber erasers use powdered pumice not for its abrasive properties, but to make the eraser more crumbly. Plastic erasers don't need that, since they just choose a polymer that already has the desired crumbing properties.Ink erasers, in contrast, contain large amounts of coarser abrasives. That's because they can't just bind the ink, but must actually debrade the surface of the paper. (We mostly just encounter this as the blue side of a double eraser.)

author: AF6LJ
author_rank: Unknown
timestamp: November 30, 2015, 01:30:56 am
content: Quote from: tooki on November 29, 2015, 11:07:25 pmRegardless; it is the wrong tool for the job.They leave crap behind.

author: tooki
author_rank: Super Contributor
timestamp: November 30, 2015, 10:35:45 am
content: I've seen natural rubber erasers leave residue, but quality plastic erasers don't. (Some are even designed specifically to not leave small crumbs.)Again, just to be clear, i'mnotarguing for the use of pencil erasers for electronics cleaning. I'm just refuting your repeated blanket statements about the properties of pencil erasers, which are incorrect as blanket statements, even if they are correct for some specific types of erasers.

author: AF6LJ
author_rank: Unknown
timestamp: November 30, 2015, 03:21:56 pm
content: Quote from: tooki on November 30, 2015, 10:35:45 amIt is the wrong tool for the job, end of story end of discussion...