Cheap multi meter lost it's smoke - Page 1
Forum section: electronics / testgear

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:00:28 pm
content: I have a cheap UEI 383 digital multi meter. Meter has always worked perfect from day one.Reason I like cheap meters is I work on a lot of vintage tube equipment. I am not going to use my fluke on them just for the fact of what happened to this meter.Instead of grabbing my trusty VTVM leads I used the DMM to test the 375 volt DC output of a tube rectifier. Not knowing there were 2 selenium rectifiers in the same circuit that was faulty. This caused 600 volts plus of AC to be present at the test point.Next thing I knew I see this big cloud of black smoke come from the meterWhat the heck, it is a cheap meter and that’s why I use them. I opened the meter to inspect the damage and found 1 component chard. Cannot read the writing on it but it looks like a filter. I can make out 10K??2U on it.Anyway the meter still functions until you select continuity mode, then in beeps continually. When the part was removed meter works as designed. But I will not use it until I replace blown component.Anyone know what this is or what to replace it with?EDIT it is maked ZNR1 on the silk screen

author: trophosphere
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:10:56 pm
content: It is probably a transient surge absorber.

author: Yago
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:14:07 pm
content: I think this is the internals of that meter (if of any help):

author: amyk
author_rank: Super Contributor
timestamp: September 05, 2014, 12:16:38 pm
content: It looks like a MOV that has functioned properly and sacrificed itself.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:26:01 pm
content: Thanks trophosphere for that thought.YagoAppreciate the picQuote from: amyk on September 05, 2014, 12:16:38 pmThats the part I was looking for but could not remember.Thanks!Now to see if I can find a replacement

author: Yago
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:33:19 pm
content: ChipWitch might have the specific part number from a teardown of the meter here:https://www.eevblog.com/forum/testgear/teardown-uei-dm383/

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 05, 2014, 12:46:33 pm
content: Quote from: Yago on September 05, 2014, 12:33:19 pmThanks, replied there and sent a pm.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 05, 2014, 04:26:27 pm
content: Quote from: Radio Tech on September 05, 2014, 12:00:28 pmhttp://www.findchips.com/search/znr10kgives 2 possibilities. With 2U it only leavesZNR10K102U - RESISTOR, VOLTAGE DEPENDENT, 825 V, 102 J, THROUGH HOLE MOUNTIf you can't find the exact part above, at least you have the specs now.

author: SeanB
author_rank: Super Contributor
timestamp: September 07, 2014, 02:07:32 pm
content: That would be about the right part, 600VAC will make it conduct and then sacrifice itself to protect the meter. Replace with a new one and you will be fine again, or if you cannot get one just use 2 lower voltage ones in series like I did with my UT61E. If you leave it out it still will work but the next overvoltage event will kill it.