Author Topic: EEVblog 121GW Multimeter Issues  (Read 564871 times)

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Offline crispus

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Re: EEVblog 121GW Multimeter Issues
« Reply #1350 on: May 27, 2021, 12:39:41 pm »
I'd also be happy to settle for an affordable PCB replacement, if that would be an option. Anything really since now I've just got a very expensive paper weight.
I would be interested in this option too since my most expensive multimeter is useless. I asked about this option in this thread couple months ago but no response so far...
Is there a board replacement available? That would give me peace of mind...

I know I'm numskull, but I look around me and I feel better.
 

Offline jancumps

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Re: EEVblog 121GW Multimeter Issues
« Reply #1351 on: May 27, 2021, 01:07:48 pm »
I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)




« Last Edit: May 27, 2021, 01:15:35 pm by jancumps »
 
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Offline J-R

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Re: EEVblog 121GW Multimeter Issues
« Reply #1352 on: May 28, 2021, 12:26:17 am »
I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)

Not sure if you're asking for info or just pointing this out, but of course future readers should push the metal shield tight against the side of the bottom case before re-assembly to avoid damaging the PTC.
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #1353 on: May 28, 2021, 12:43:25 am »
FYI, I have asked KaneTest for comment.
 

Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #1354 on: May 28, 2021, 02:07:25 am »
FYI, I have asked KaneTest for comment.

They have come back and said they can't see how it could have survived the factory calibrator HV test if it was a manufacturing error. But they have agreed to replace it. So email me your courier details.
 
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Offline jancumps

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Re: EEVblog 121GW Multimeter Issues
« Reply #1355 on: May 28, 2021, 10:11:10 am »
I've tried to make a bit more targeted photos of my meter (SN 180701835 that is behaving well).

I can see some damage on that PTC and the shrink around it.

(the DMM case side is not damaged. What looks like damage is shadow of the component)

Not sure if you're asking for info or just pointing this out, but of course future readers should push the metal shield tight against the side of the bottom case before re-assembly to avoid damaging the PTC.
I wasn't asking. Just showing how the PTC area and shield looks like in my meter. It may help in the analysis.
 


Offline Archon

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Re: EEVblog 121GW Multimeter Issues
« Reply #1357 on: June 04, 2021, 06:23:38 pm »
Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?
 

Online HKJ

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Re: EEVblog 121GW Multimeter Issues
« Reply #1358 on: June 04, 2021, 06:47:43 pm »
Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

As far as I know the only real issue was with the rotary switch and it was fixed in a couple of months.
Over time there have been some software issues, but nothing you could not get around by using manual range and because the 121GW allows software updates it has been possible to fix these issues on all meters sold.

Note: I do not rate the 121GW as the best DMM ever, but it is a very good meter and like any meter it is not perfect. I do have about all high end meters on the market and I would not rate any of them a clear winner.
 
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Offline EEVblog

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Re: EEVblog 121GW Multimeter Issues
« Reply #1359 on: June 06, 2021, 08:45:07 am »
Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

The PCB shim issues was limited to the first few thousands PCB's. That included all the Kickstarter units and a bunch of the first normal production units. All future PCB's have been the correct thickness and the issue was resolved. All units bought today do not have this issue, no one has old stock.
 
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Offline nuclearcat

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Re: EEVblog 121GW Multimeter Issues
« Reply #1360 on: June 08, 2021, 07:37:36 am »
Hi, new user here. Is this the right place to ask if the above issue was related to manufacturing during the kickstarter? Did it result in a fix of some sort? If I were to order a 121GW right now, can I have confidence it won't have such an issue?

The PCB shim issues was limited to the first few thousands PCB's. That included all the Kickstarter units and a bunch of the first normal production units. All future PCB's have been the correct thickness and the issue was resolved. All units bought today do not have this issue, no one has old stock.
Sorry to ask here, but where to get this shim? I am one of "early kickstarter users", used multimeter very rarely, and i started to get contact issues (i have to press on knob to make multimeter on after changing mode).
Maybe there is some drawings and anything i can do DIY?
« Last Edit: June 08, 2021, 08:15:33 am by nuclearcat »
 

Offline BrianG61UK

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Re: EEVblog 121GW Multimeter Issues
« Reply #1361 on: July 04, 2021, 07:51:55 pm »
Using  low-Z the voltage disappeared.  I read up on ghost voltage.  Yep, that was what I saw.
Thanks for your assistance.
Surely that means your ground is a high impedance, which means it's not ground at all and could be dangerous if you use it to ground something that needs a ground for safety reasons.

It could be induced voltage from a parallel running cable, however I'd recommend it's investigated by a qualified electrician using an installation tester.

I was forgetting that the 121GW in Low-Z mode is brain dead and shows zero even when there is a low voltage present.
 

Offline ShortCircuit

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Re: EEVblog 121GW Multimeter Issues
« Reply #1362 on: September 28, 2021, 10:44:04 pm »
I just checked my meter and mine too has the plastic insulator deformed by squishing the PTC, not enough to do damage though. Looks like the metal shield with insulator wasn't glued to the side of the case, which would've prevented this. I took the liberty of applying a piece of inflammable PSA tape to secure it to the case and prevent subsequent smoke egress and grief.
 

Offline oliv3r

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Re: EEVblog 121GW Multimeter Issues
« Reply #1363 on: September 30, 2021, 07:16:22 pm »
Hi everyone.
It seems my 121GW just broke, and I have no idea how or why :S
...

Hey @vyruz I'm sad to see your broken DMM :( I recall you got a replacement however, yeah? Do you still have the broken one? Would you want to offer it for science? :) Some of us are curious to get hi-res pictures/scans of the PCB; which would require removing all components first of course. Only a ruined DMM should be used for that of course :)
 

Offline ShortCircuit

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Re: EEVblog 121GW Multimeter Issues
« Reply #1364 on: October 16, 2021, 09:00:09 pm »
Did anyone else notice that turning the bluetooth on causes the meter to cool by more than half a degree C and turning it back off causes it to heat back up to previous half a degree higher temperature?
 

Offline bicycleguy

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Re: EEVblog 121GW Multimeter Issues
« Reply #1365 on: October 18, 2021, 04:26:31 am »
@ShortCircuit
Good find!  and I thought I was picky.  Mine is almost exactly 1 degree F  :D
 

Online Kleinstein

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Re: EEVblog 121GW Multimeter Issues
« Reply #1366 on: October 18, 2021, 08:55:41 am »
The meter should not cool down form turning on blue-tooth. If at all the temperature reading may change, by some interference.
The temperature reading is likely not that accurate anyway, so I would not worry much about this part. The question is if it effects other measurements too ?
 

Online Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #1367 on: October 18, 2021, 12:56:18 pm »
Did anyone else notice that turning the bluetooth on causes the meter to cool by more than half a degree C and turning it back off causes it to heat back up to previous half a degree higher temperature?

I can confirm this happens on my 121GW.  Drops about 0.6C within a few seconds when BT is turned on, and rises again very quickly after it is turned off.
The thermistor NTC1 which I presume is used for temperature sensing is at top right of the PCB (looking from the back) and BT module at top left.
I hooked up some fine wires so I could monitor B+, VDD (3.6V), and VDD_P (3.3V) with the case closed.  The thermistor is part of a voltage divider on VDD.
VDD and VDD_P do not really change when BT is enabled, but I do see a small drop on B+ due to the extra load.
VREF+ on the STM32 connects to VDDA which connects to VDD_P.  No idea... maybe a firmware issue with code trying to correct for something no longer relevant?
 

Online Kean

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Re: EEVblog 121GW Multimeter Issues
« Reply #1368 on: October 18, 2021, 12:59:51 pm »
The temperature reading is likely not that accurate anyway, so I would not worry much about this part. The question is if it effects other measurements too ?

It is used for CJC with the thermocouple, so thermocouple readings also drop by the same amount.
Weird that they put the thermistor so far away from the input jacks when it is used for CJC.
« Last Edit: October 18, 2021, 01:01:27 pm by Kean »
 


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