Author Topic: Faulty EEVBlog DMMs (both types) - where do I return for repair? (Read 2891 times)

sabia · « **on:** October 05, 2019, 04:20:34 pm »

Hi, all

I've tried to DM Dave/EEVBlog on here but to no avail, so I will try on the forum, in the hope to get a reply.

Basically I have bought 2 DMMs from EEVBlog, one Brymen and one 121GW. Unfortunately both meters have now gone bust, even though they have seen little use, and never excessive volts/currents.

The Brymen has all the top buttons near the screen faulty, rendering it completely useless as I can't change ranges, modes, etc.

The 121GW doesn't measure AC voltage (probes one way gives 0V and swapping the probes gives a different result!) And capacitance measurement only works on some ranges...on others the screen just flashes a comma.

I thought this was a FW issue for some time, but after updating to version 2.0 I have given up, and I can't live with these meters in their current state. Nor will I buy another given the "quality" that mine has shown. Besides, the support is as bad as the DMMs at this point, as I cannot for the life of me fine the contact information as to how and where to return the meters for repair. Dave doesn't respond on DM.

Does anyone on here know of any email address etc where I can contact to start a repair process? And has anyone else had problems with these DMMs? I would hope that I have been just extremely unlucky, as I cannot imagine Dave putting his brand on something this unreliable...

Thanks.

Kind regards,
Olav Barros Storstrøm
Sabia AS

Terry01 · « **Reply #1 on:** October 05, 2019, 04:42:31 pm »

Return them to the shop where you purchased them....

sabia · « **Reply #2 on:** October 06, 2019, 05:23:40 pm »

I bought them from Dave/EEVBlog. One via Amazon I think, the other via his Kickstarter campaign. He doesn’t have a physical store. Oh, and you are now on Dave’s forum, in case you didn’t know.

Terry01 · « **Reply #3 on:** October 06, 2019, 05:42:49 pm »

sabia · « **Reply #4 on:** October 06, 2019, 05:56:34 pm »

You’re a bundle of help, Terry. Such insight

Terry01 · « **Reply #5 on:** October 06, 2019, 06:06:49 pm »

Glad I could be of assistance my friend. Do you need help with anything else?

Simon · « **Reply #6 on:** October 06, 2019, 06:28:23 pm »

The amazon one can go back to amazon, Dave has a store on this site. I an truly surprised that you have these issues. I sell these too and no problems from anyone and I use them myself. The BM235 is just the same as the one Brymen make that will have been sold in very hight volumes more than the 121GW

EEVblog · « **Reply #7 on:** October 07, 2019, 01:08:49 am »

You can return both of them to here with your name and details and fault.

David Jones - RETURNS
PO Box 7949
Baulkham Hills NSW 2153
AUSTRALIA

I'll reimburse you via PayPal for the postage, just sent me a paypal invoice at dave AT eevblog DOT com
I'll check them over and then will decide a course of action.

Both of these faults you describe are completely new. Faults in either unit are rather rare, let alone having both fail for the one customer.

Electro Detective · « **Reply #8 on:** October 07, 2019, 01:46:16 am »

Consider to switch on the camera and upload proceedings to Youtube,

this one sounds interesting..two meters no go?

Simon · « **Reply #9 on:** October 07, 2019, 06:46:37 am »

Yea, such a coincidence.

don.r · « **Reply #10 on:** October 07, 2019, 02:58:33 pm »

Norway... condensation?

Simon · « **Reply #11 on:** October 07, 2019, 03:16:53 pm »

No, that cold is dry

don.r · « **Reply #12 on:** October 07, 2019, 03:44:28 pm »

Bring a cold, dry meter into a hot, humid room and... enjoy.

Investigating the faults would make for an interesting video, though.

Simon · « **Reply #13 on:** October 07, 2019, 05:07:56 pm »

If there are faults. this is one mighty coincidents.

sabia · « **Reply #14 on:** October 07, 2019, 09:16:04 pm »

Hi again!

I have now made 2 videos.

I think you'll all agree that the BM235 has knackered buttons. And the Lo Z mode only shows dashes.

https://youtu.be/AFoS8A5t2CM

As for the 121GW I had 2 issues. One was that sometimes the meter won't measure capacitance. But only when they are in a (obviously un-powered) circuit. Other DMMs can, though...I guess it depends on how much leakage path (in the form of resistance) there is across the capacitor vs. the current output of the DMM. But let's leave that - the main issue are the AC measurements in mV mode. If there is a DC offset then the readout is wrong. I'm starting to think that maybe the AC coupling is done in firmware or something? Seems to happen when the signal exceeds 2V or thereabouts.

https://youtu.be/G6P6W2s4etA

The 12GW is somewhat fancier than my other DMMs, and my issues with that DMM can well be down to me, although I have been using instruments for 25 years...and to be honest the manual does leave a bit to the imagination here and there... Can anyone explain what exactly the DC+AD mode does? I get exactly the same result in DC+AC mode as I get in DC mode... (Given a test signal of 1kHz sine with a small DC offset).

In terms of environment the meters go with me everywhere my tool bag goes, but I only ever work indoors, so I doubt that is the issue. The 121GW travel in its pouch anyway.

Dr. Frank · « **Reply #15 on:** October 07, 2019, 10:04:55 pm »

Quote from: sabia on October 07, 2019, 09:16:04 pm

Hi again!
...

As for the 121GW I had 2 issues. One was that sometimes the meter won't measure capacitance. But only when they are in a (obviously un-powered) circuit. Other DMMs can, though...I guess it depends on how much leakage path (in the form of resistance) there is across the capacitor vs. the current output of the DMM. But let's leave that - the main issue are the AC measurements in mV mode. If there is a DC offset then the readout is wrong. I'm starting to think that maybe the AC coupling is done in firmware or something? Seems to happen when the signal exceeds 2V or thereabouts.

https://youtu.be/G6P6W2s4etA

Well, there are various methods inside DMMs and LCR meters, to measure the capacitance.. and some are able to measure something in-circuit, others maybe even something correct, but most methods require to test the capacitor out-of-circuit.
So your statements, that it does not measure capacitance, or not correctly , or other DMMs can measure inside a circuit, is too generalized, at least it's an inaccurate description of the problem and the environmental condition.
I would not call that a defect, but simply a wrong usage of the DMM.

It's the same story with ACV measurements.. First you claim, that ACV does not work (..at all..), only zeros.
After watching your video, it's obvious, that ACV works correctly... 100mV_pp is measured correctly as about 36mV_rms.

But as as soon as you apply DC of several volts (!!!) to the 50mV AC range, which is not intended at all (AC+DC for 5V and upwards only!), the opamps and/or the digitizing type AC/DC converter in the Hynix chipset is/are completely saturated, displaying zero Volt_AC... 4V_DC is a 50 fold overload on the 50mV_AC range.. good for you, that the 121GW is well protected.
It's clear, that if you reverse this illegitimate DC signal, you'll get a different failure reading.

If I remember correctly, there already had been some discussion on the behavior of measurements on AC+DC signals.. because it has no proper overload indicator for DC, and the allowed DC and AC amplitudes are not specified correctly .. and yes, the manual is not detailed at all at this point.

Maybe you test your 121GW first under proper conditions, before you send it to Dave.

Frank

sabia · « **Reply #16 on:** October 07, 2019, 11:17:11 pm »

Thanks, Frank!

You make some good points, and clearly you know this unit well. But I think it's unrealistic to expect the user to know what the chipset is and the inner workings in order to use a DMM...!

If I want to measure the AC voltage I expect it to be AC coupled, simple as that. The manual only states he following:

"mV, Ohm & others: 600 V DC/AC RMS PTC & MOV Protection"

Well protected indeed!

Still...if the mV AC mode had a proper AC coupling (i.e. one that removes DC!) I should expect to measure a few mV AC with great resolution even with a large DC offset. And there can be no "illegitimate signal" if the "legitimate" signal range isn't specified in the manual of the DMM in any way.

Well, I will read up on the DC+AC measurements on here, thanks for the tip

EEVblog · « **Reply #17 on:** October 08, 2019, 12:25:59 am »

Quote from: Dr. Frank on October 07, 2019, 10:04:55 pm

It's the same story with ACV measurements.. First you claim, that ACV does not work (..at all..), only zeros.
After watching your video, it's obvious, that ACV works correctly... 100mV_pp is measured correctly as about 36mV_rms.

But as as soon as you apply DC of several volts (!!!) to the 50mV AC range, which is not intended at all (AC+DC for 5V and upwards only!), the opamps and/or the digitizing type AC/DC converter in the Hynix chipset is/are completely saturated, displaying zero Volt_AC... 4V_DC is a 50 fold overload on the 50mV_AC range.. good for you, that the 121GW is well protected.
It's clear, that if you reverse this illegitimate DC signal, you'll get a different failure reading.

Correct, there is nothing wrong with the ACmV measurement here.
I just tried some other meters I had nearby, BM235, Keysight 1282A (same HY3131 chipset), Keysight U1272A, and Brymen BM869 and they all do the exact same thing with a large offset on mVAC mode, they die around 1V or 2V DC offset on the mVAC range.

EEVblog · « **Reply #18 on:** October 08, 2019, 12:28:38 am »

Quote from: sabia on October 07, 2019, 09:16:04 pm

Hi again!

I have now made 2 videos.

I think you'll all agree that the BM235 has knackered buttons. And the Lo Z mode only shows dashes.

https://youtu.be/AFoS8A5t2CM

The LowZ mode is supposed to only show dashes, and it needs about 10V or more to work, so if you are trying to measure low voltages with this mode then it won't work.
As for the button, have never seen them not work. Silly question, but are you pressing them firmly enough? If so then looks like a genuine fault.

sabia · « **Reply #19 on:** October 08, 2019, 09:16:14 am »

Quote from: EEVblog on October 08, 2019, 12:28:38 am

The LowZ mode is supposed to only show dashes, and it needs about 10V or more to work, so if you are trying to measure low voltages with this mode then it won't work.
As for the button, have never seen them not work. Silly question, but are you pressing them firmly enough? If so then looks like a genuine fault.

Thanks. I guess the 121GW is fine then

Perhaps I expected too much from the AC coupling, given that you helped design it

At any rate the BM235 is definitely gonsky, as no matter how hard I press the buttons nothing happens. But given that it seems to be an isolated case I'm not sure it's worth sending it half-way across the globe...and back! The postage will be more than a new meter costs...and then I'll get customs fees and VAT on top.

negativ3 · « **Reply #20 on:** October 08, 2019, 10:20:53 am »

Don't turn it on, take it apart!

Collaborate and repair?

Simon · « **Reply #21 on:** October 08, 2019, 10:45:19 am »

if its under warranty best not.

sabia · « **Reply #22 on:** October 08, 2019, 10:05:40 pm »

I've opened the BM235 and inspected it with my Mantis, nothing much to report apart from a repair on 2 diodes and a possible track repair (unless that is spillage from soldering the nearby fuse holder). One of the chips has a small white mark added to it.

I cleaned the board, then I added two wires to measure the contact resistance of the select/backlight button when closed. They were soldered through nearby vias. Contact resistance came in at about 40 ohm, which sounds reasonable to me for a membrane "pill" switch on gold. Measured the contact resistance before and after re-assembling. No response to the button. I also tried shorting the wires, still no response.

It's dead for sure. But I don't see any point in spending lots of time on a €120 meter...

Thanks for the help, everyone! Dave, I'll send it to you if you want, if not it will go in the nearest suitable recycling bin.

giosif · « **Reply #23 on:** October 08, 2019, 11:22:25 pm »

"Chuck" the BM235 over this bin here, please.

Heck, if it doesn't involve too high costs on shipping between Norway and UK and I somehow manage to repair it, I'd be happy to send it back to you.


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Author Topic: Faulty EEVBlog DMMs (both types) - where do I return for repair? (Read 2891 times)

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