Electronics > Repair

repairing DMM's

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Mar:
he every one ..
is there any post in here talk about repairing Digital multimeter ??
i have 4 units .. every one miss something to work good .. i hope that some ppl can share there knowledge about this ...

ejeffrey:
Please provide useful information.  What are the models of DMMs, what is wrong with them, and what will you use them for.

Mar:

--- Quote from: ejeffrey on May 13, 2013, 04:26:12 pm ---Please provide useful information.  What are the models of DMMs, what is wrong with them, and what will you use them for.

--- End quote ---

ofcource i will .. but wonder if here should i write about this ? .. any way ..

first  : uni-t ut70b with no signs of live .. but the light work .. no numbers on screen ..

second is UT70A ..  always beebs on continuity test or when testing resistance   ..wrong numbers in other tests  .

third another UT70A ... no sign of life at all ..

last one is Mastech 5 in 1 ... this unit is work but problem on the screen .. the ( dot and upper right symbols are clear on the screen but every thing else is very hard to see at all angels  ... wonder if there is something control the contrast in it ??

i check all the fuses .. try to check transistors and diodes also ....
maybe one of the IC need change .. TL062 or 10583 or something else .. ....
especially for the last one with very low contrast in screen ..


retiredcaps:
Personally, I would be happy to help if I can.

Right now, I'm trying to learn more about how multimeters work so repairing them is a good test of my understanding.

I will make a few suggestions so that everyone's time and efforts are best utilized.

1) Pick one multimeter to work one and make a new post.  This avoids confusion because I don't have the multimeters in front of me and I can't keep track of what was done to what unit.  For example, let's pick the third  UT70A ... no sign of life at all

2) In that new post, provide clear focused pictures and/or service manuals/schematics so we have all the necessary information and don't have to go searching for them.

3) Tell us what country you live in by filling in your profile.

4) Tell us what tests work (i.e. DCV, ACV, etc) and what doesn't work so we can narrow down the problem.

While ModemHead hasn't documented any Uni-T repairs, his blog contains excellent information on other multimeter repairs.  You can learn a lot and get ideas from

http://mrmodemhead.com/

PA0PBZ:
About the last one with the faint display: take it apart, take the display off and clean the pcb, the display and the zebra strips with alcohol.

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