Agilent U1211A Clamp Meter Failure - Page 1
Forum section: electronics / testgear

author: Cones
author_rank: Regular Contributor
timestamp: March 30, 2013, 03:24:58 pm
content: Hi,I bought this Agilent U1211A clamp meter as untested and possibly not working on ebay.Well the package arrived and as soon as I opened it up I could smell that something was burnt inside it!But it only cost £10 plus post so not to worry too much.It even came fitted with a battery. On power on the display works and the Ohms range with the probes connected is working perfectly. The problem is with the DC and AC volts ranges.As you can see below it has had a major overload of some description.GoodNot so good.Major burning to the PCB tracks under the range selector switch.SwitchInput PCBDisplay PCBSo any guesses to how the previous owner managed to overload a 1000V input meter? Perhaps on something higher than 1000V?I suspect it made them jump when it went bang!Now is it possible to repair PCB traces and how do you attempt to do so?I have not tested the clamp part yet. I need to fix one of the CT wires I broke removing the PCB. It did not seem very well attached to start with.More pictures of the parts here :-http://s699.photobucket.com/user/cones_stuff/library/Agilent%20U1211A%20Clamp%20MeterThanksMark

author: Wytnucls
author_rank: Super Contributor
timestamp: March 30, 2013, 04:34:28 pm
content: I would test the clamp. If it works, I would keep it just for the AC/DC amps. If not, I would unsolder anything useful and throw the rest away.

author: Cones
author_rank: Regular Contributor
timestamp: March 30, 2013, 06:06:26 pm
content: Hi,I've cleaned away all the burn marks and put a tiny dab of solder on the ends of the tracks. Fixed the snapped off CT wire and given everything a good clean.Re assembled and runs few tests. Everything now works exactly as it should.DC volts and AC volts are fine (Mains voltage agrees with my Fluke).Clamp works great on the house main incoming cables (easy to get at a single core). Frequency display works.Diode test works, Capacitance measurements looks good.Resistance is spot on with my decade box. Continuity works although is a bit slow.I will probably only use it for the clamp feature though as I have other meters for everything else.It is interesting that it is still working after all that abuse though.ThanksMark

author: SeanB
author_rank: Super Contributor
timestamp: March 31, 2013, 05:57:40 am
content: TO fix the damaged board clean it off thoroughly and apply a thin coating of 2 part epoxy and use a credit card to scrape it level before cure. Then buff with a clean cloth and alcohol when cured until the contact areas are clean of the epoxy. Then you can replace the blown VDR's and see if it works on voltage then. They probably plugged it into a 11kV line in a substation. Most likely the probes blew up as well.

author: saturation
author_rank: Super Contributor
timestamp: March 31, 2013, 01:02:33 pm
content: Great job. Typical transient suppression devices burn out and fail open, after shorting the majority of the fault current to ground. So, unless you check those elements, the input CAT protection may not longer be valid.

author: Cones
author_rank: Regular Contributor
timestamp: March 31, 2013, 06:20:00 pm
content: Hi,Thanks for the comments.So what exactly is one of these then? As it seems the second one is damaged and may need a replacement.The PCB is marked SPG1 and SPG2. Is the SP 'Surge Protection' something or other?

author: robrenz
author_rank: Super Contributor
timestamp: March 31, 2013, 06:29:49 pm
content: My guess is they areSParkGaps

author: Wytnucls
author_rank: Super Contributor
timestamp: March 31, 2013, 06:31:32 pm
content: Yes, Spark Gap or Gas Discharge Tube (GDT). They normally would have to be replaced after some serious stress.

author: SeanB
author_rank: Super Contributor
timestamp: March 31, 2013, 06:50:26 pm
content: Look inside a telephone surge arrestor for some replacements. A lot bigger but plenty man enough. Otherwise almost any dead fax machine will have some on the phone side as protection. Probably the right devices.