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Agilent U1211A Clamp Meter Failure

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Cones:
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.  :-DMM

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.



Good


Not so good.



Major burning to the PCB tracks under the range selector switch.


Switch


Input PCB


Display PCB


So 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!  :-BROKE

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%20Meter

Thanks

Mark

Wytnucls:
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.

Cones:
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.  :-DMM

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.


Thanks

Mark

SeanB:
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.

saturation:
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.

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