EEVblog 121GW Multimeter Issues

[jcosper]

Hello all,

My GW121 recently starting misbehaving. I pulled it out after a 2 week vacation, and now it beeps constantly and displays "LEAD" in resistance/capacitance/continuity modes (but diode mode doesn't beep and seems to work). It also happens in voltage measurement mode, and some current measurement modes, but not all.

I changed the batteries (standard cells) with no change. I tried different probes (and no probes) with no change. Fuses test good. My meter has FW 2.05 sn 210403113. I didn't find mention of this code in the manual, and no relevant hits searching. Any thoughts? AFAIK, it was fine when I stored it away after last use, but something gave up.

Thanks!
Jay

[J-R]

It is odd that it doesn't beep in diode mode.
What current modes does it beep?

Typically the first step is to thoroughly clean the A and mA jacks.  Has it been used in a dirty environment?
Beyond that you could return it if it's still under warranty.
If not, disassemble and inspect the "Input Warning Circuit" as shown on the schematic.  The resistances involved are pretty high, so again I'd look for some contamination as the first suspect.
https://www.eevblog.com/wp-content/plugins/download-attachments/includes/download.php?id=11618

[EEVblog]

Typically the first step is to thoroughly clean the A and mA jacks.  Has it been used in a dirty environment?

Yes, always the first step.

[jcosper]

It is odd that it doesn't beep in diode mode.
What current modes does it beep?

Typically the first step is to thoroughly clean the A and mA jacks.  Has it been used in a dirty environment?
Beyond that you could return it if it's still under warranty.
If not, disassemble and inspect the "Input Warning Circuit" as shown on the schematic.  The resistances involved are pretty high, so again I'd look for some contamination as the first suspect.
https://www.eevblog.com/wp-content/plugins/download-attachments/includes/download.php?id=11618

Thanks for the input. It beeps in uA but not A/mA (shows 0.07mA with nothing connected). I really only use it in my home lab. I guess I'll start tearing it apart and give it some tlc. I have owned it for a couple of years now.

[J-R]

In that case I think I would focus on the A 500mA jack first.
No need to open it up for the cleaning.  Just scrub the inside of the jack to start.

[jcosper]

In that case I think I would focus on the A 500mA jack first.
No need to open it up for the cleaning.  Just scrub the inside of the jack to start.

I cleaned the jacks and now Ohm/continuity/A/uA don't beep and display "LEAD" but capacitance and voltage measurements still do. I'll scrub it some more to see if I can get all functionality to recover.