Sniff. I killed another DMM :(

[paulca]

Plz post some pics of the places where the magic smoke escaped. There is something charming about it.

Also as the others have already said it's strange the meter failed in the ohms range. Usually it has 250 - 300 v protection.

Anyways do post some pics to analyze and see the built quality of the multimeter (it's interesting)

There was no smoke!

However, the more screws I removed from the meter the more it smelt of "hospital", strong antiseptic.   TCP?

I will promise some photos.

[Gyro]

This is where having an electrician's CAT rated  two pole voltage tester at hand comes in really handy. DMMs (or their operators) are too error prone for live stuff. By all means use a DMM, but use a tester to prove dead first.

[Jwillis]

What meter was it? It shouldn't happen. A good meter must survive high voltage (meaning AC mains) input in any mode.

I would like to know what brand it was to so i can avoid it. Never had a failure in a meter when voltage is applied in the Ohms setting.
Destroyed one with over voltage once . But 3kV will do in just about any DMM.

[AnalogTodd]

Buy a Fluke and it will be the last meter you ever need. I've had mine for many years, haven't killed it yet.

The labs at the semiconductor company I worked at for decades had Fluke 87 (various generations) sprinkled around like crazy. I bought one for my home use, and gifted one to my son as he got into his job (IT, both keyboard and hardware side). As said, these things are pretty much impossible to kill, hence the lab manager purchasing them for our use. Believe me, there are plenty of engineers and techs who can kill equipment without much trying.

[theHWcave]

Flukes are expensive. I would go for a Brymen, built at least as good and generally more capable on the same price point. As a beginner meter, I always recommend the BM235. Built like a tank. I have used mine for years now. £71 here for example (no affiliation) https://telonic.co.uk/product/brymen-bm235-professional-multimeter-cat-ii-1kv-cat-iii-600v/ . I bought my Rigol scope from them and a BM869s and their service was good.

[mwb1100]

This teardown of an Extech 350 shows several PTCs and MOVs on the input as well as 900K (through three 300K SMT resistors) on the input:

  - https://www.eevblog.com/forum/testgear/extech_s-new-ex350-a-first-look/msg959909/#msg959909

Should that have handled the situation better?  Is there some defect in the input protection design on the 350? Maybe the SMT resistors aren't up to the task?

[james_s]

Might be worth contacting the manufacture, they may be willing to replace it.

[Swainster]

FWIW, the only DMM I've personally owned from new which failed is a fluke. That said, I've seen quite a few unit-t DMMs fail on the job, though not while I was using them.

Regarding the fluke (115), it failed while on the shelf - one day I turned it on and it was showing cal-err and was totally unusable. As such, I'd say go with the brymen. At least you won't be so annoyed if it decides to spontaneously fail on you. To fair to fluke, I also have a couple of decades old models which have never missed a beat.

[paulca]

I went for the Brymen BM235. 

[paulca]

Does the following link work?  Post-mortem photos.
https://photos.app.goo.gl/Jt4soTyt2fnhkUp1A

I measured the fuses.  2 Ohm and 1.2 Ohm according to my £10 stand in.

I measured the input resistor network, 890K Ohm.

Given where the rotary knob melted, if it melted during the "incorrect use", it would have been over on the A / mA portion of the dial.  There are visible marks and damage to the solder mask in that area.

However.  That melted spot is also directly under the battery compartment.  (EDIT Just on the complete otherside of the board Paul!)  The meter has already suffered cell leakage damage (which is when I oddly lost the continuity buzzer), but the meter was cleaned and worked for 3 years since.

I did also replace a pair of Duracells in there that "felt" a bit waxy to the touch and a few flakes of white crust... about a month ago.

Is it likely the "incorrect use" was just coindidentally on the slow progression of battery acid eating the rotatory dial structure?

Why then the strong smell of anti-sceptic.  I mean it "stank" on opening.  Very obvious.  Is that what battery acid eating rotary dial and solder mask smells like?

On warranty, given the previous leakage damage and the meter being 5 years old.  The best I'd foresee is just being nice and asking Extech if they want the meter back for fault mode diagnosis.  I doubt I'd get a replacement.

[paulca]

I did call ExTech to see if I could get a replacement rotary switch.

"We don't sell parts for that meter.   You could return it for service and repair and that "might" be possible."

That's a dead end.  Best case I spend the money to return it.  They tell me it's a goner and offer me 30% of a new one.

So it's eWaste or make my own contacts.

[joeqsmith]

Note how the traces connecting the pads of the rotary switch route such that the contact run over them.  They have cut through the mask to copper.   Also note how they placed the vias centered on the pads, right inline with the contacts.   Turning the switch with the meter attached may have done it in.   

Enjoy your new meter.

[Jwillis]

I did call ExTech to see if I could get a replacement rotary switch.

"We don't sell parts for that meter.   You could return it for service and repair and that "might" be possible."

That's a dead end.  Best case I spend the money to return it.  They tell me it's a goner and offer me 30% of a new one.

So it's eWaste or make my own contacts.

I am  really surprised its an Extech . Considering the price one would expect a lot more. Think I'll stick to Mastech , and Brymen . Have one Fluke and its a nice meter but to much for my budget to get a second .

[BeBuLamar]

FWIW, the only DMM I've personally owned from new which failed is a fluke. That said, I've seen quite a few unit-t DMMs fail on the job, though not while I was using them.

Regarding the fluke (115), it failed while on the shelf - one day I turned it on and it was showing cal-err and was totally unusable. As such, I'd say go with the brymen. At least you won't be so annoyed if it decides to spontaneously fail on you. To fair to fluke, I also have a couple of decades old models which have never missed a beat.

I have encountered several Fluke meters that failed. Those include the 116, 87, 189 2 of them, 287 3 or 4 of them.

[Swainster]

Haha, the only other fluke I've bought new is a 189. Although it hasn't failed yet, it seems like I'm good at picking the 'exceptions that prove the rule'.

BTW, running through the calibration procedure got the 115 running again, but improvising 600VAC required a bit of improvisation. Presumably some eeprom data had been corrupted... while sitting on the shelf (or more likely when first turned on with a low battery after sitting on the shelf for a few months, though there was no battery leakage).

[alm]

Haha, the only other fluke I've bought new is a 189. Although it hasn't failed yet, it seems like I'm good at picking the 'exceptions that prove the rule'.

The plural of anecdote is not data. There have been a *lot* of Fluke meters produced over decades, so if you look in the right places I'm sure it's easy to find many broken meters. Brymen has been around for much shorter and produces in much smaller volumes, so naturally there will be fewer broken Brymen meters around.

All brands have failures. To measure the failure rate you need access to data on a much larger, less biased, sample than any individual is likely have access to unless they work at a large distributor and manufacturer, and are probably not allowed to talk about it.

[Swainster]

Totally agree! Just to be clear, my remark was 'tongue in cheek'. In fact, I am more of a fluke enthusiast than a detractor, as the pride of my TE collection are both Flukes. That said, my personal opinion is that if you are buying new,  Brymen DMMs offer better bang for buck for general hobby/DIY use.

[dietert1]

Note the position of the Hz range next to the V~ range on the BM869 recommended above. If we want to learn something from all this..

Regards, Dieter

[paulca]

I want to point out.  The meter was not connected to the test device while I rotated the dial.

[David Hess]

The ohms mode on better multimeters will withstand hundreds of volts without damage.

My Beckman RMS225 specifies overload protection of 500 volts DC or AC RMS for all ohms ranges.  My Tektronix DMM916 specifies 850 volts peak for all ohms ranges.  My very old Tektronix DM501 is protected by a 1/16 amp fuse, which I replaced with a pair of 28 volt grain of wheat bulbs, but the slightly later DM502 is protected to 130 volts DC or AC RMS continuously, or 250 volts DC or AC RMS for 1/2 hour, using a very small 120 volt filament lamp.

[paulca]

Been using the new BM235 for a bit now.

Found a few features I love.  The fact the auto power off is "smart".  So if you leave it monitoring a battery voltage, it stays monitoring it.

Also, if you enable the "REC" function for MAX, MIN, AVG, it beeps every time the voltage changes.  That can be very useful when charging, say, lithium cells and a voltage rise might be nice to "hear".  Additionally it it starts beeping rapidly, the voltage is changing rapidly.

The only downside with that feature is the audio beep times out after about a minute.  It did give me an idea for adding sound to battery chargers and BMSes.  So you CAN take your eyes off them when abusing them.