Broken UNI-T UT61c or am I missing something?

[retiredcaps]

Q12 and Q11 appear to be short between base and emitter,

I have been fooled by in circuit measurements before so I can't say 100%. 

Maybe ask electronupdate to make the same measurement on his UT61C to see if the two above are supposed to be shorted or not?

Also, did you measure "R22" off SGND (it looks like SGND is connected to R15 which is 102 or 1k)?

[mrkva]

I've wrote him an e-mail, hopefully he will find some time and energy for me
I measured the 1k resistor, it reads out correctly. Only thing left are those transistors.

[electronupdate]

If Q11 and Q12 are such that the base and emitter are on one side, and the collector on the other....they too are shorted on my meter.

If you are reading a voltage on the millivolt range, however, does that not imply that the IC thinks there is a voltage on the input pin...

There is a REFI and REFO pin (reference voltages), not sure if they would affect a measurment.  Also any floating grounds or missing voltage rails on the IC could cause strange readings.

Given the poor quality of the solder on the sample you may want to retouch each connection.  Have you looked at the IC?  any bridged or floating pins?  If you have access to a hot-air rework station you might want to reflow all of the joints.

However, as the meter came from a reasonably decent supplier (i think you mentioned DX)  it might be a good time to ask for a replacement...

[retiredcaps]

The only thing I can think of right now is that maybe the Q2 and/or R22 doesn't have continuity to COM/ground?

[retiredcaps]

If Q11 and Q12 are such that the base and emitter are on one side, and the collector on the other....they too are shorted on my meter.

Thanks for confirming the readings.  With respect to "in circuit" readings, I now live by

Fool me once, shame on you.
Fool me twice, shame on me.

[electronupdate]

and.... now that I have reassembled my meter I can report it is now just as broken  as the OP's.


How strange.  There must be something quite fragile in the meter.  I re-flowed some suspect joints, however, the meter remains broken.

[retiredcaps]

How strange.  There must be something quite fragile in the meter.

Sorry to hear a good deed and trying to help someone has resulted in a non working multimeter.

I suggest doing a follow up video.

Taking apart a multimeter shouldn't kill it.  I recently worked on a Fluke 77 III, with no regard to ESD handling, and I must have taken the thing apart at least 30 times (including the lcd with self tappers), washed it 3 times with IPA, and soldered the pcb and it survived no problem.

The problem with "warranty" now is the potentially high shipping costs and long delay back to the seller.

PS. Am I the only one who thinks that the multimeter should read 0.000 when it is on DCV with no input?  Virtually every multimeter I have used shows 0.000 on DCV.  Even on DC mV, it will settle close to 0.0 given enough time.

[retiredcaps]

On a related note, can you imagine if Dave got the UT61C for the $99 shootout instead of the UT61D?  You be hearing WAHOS a lot (like the $50 Global Specialty).

It is funny how the UT61C, D and E are all perceived.

[mrkva]

Oh I am sorry for your meter. This is terrible
Why do you think the current measurement appears to be OK, even though it is the same pin?

[dr_p]

clean the rotary switch's contacts. Check for bent/broken elements.

[electronupdate]

No, not at all terrible... now I have another mystery to solve some day ...  that meter was not one of my main units.

Does give good indication that your troubles are not one-off and there is something more systemic going on. It may have some mechanical basis as taking a meter apart should not break it.

Oh I am sorry for your meter. This is terrible
Why do you think the current measurement appears to be OK, even though it is the same pin?

[mrkva]

Unfortunately, this was meant to be my main unit - step up from 10$ meter. Quite unsuccessful...
Would be great if we could figure it out somehow, maybe we are not alone with this issue.

[mrkva]

No, not at all terrible... now I have another mystery to solve some day ...  that meter was not one of my main units.

Does give good indication that your troubles are not one-off and there is something more systemic going on. It may have some mechanical basis as taking a meter apart should not break it.

Actually, it would be really great if you would make a video as retiredcaps suggests, it might bring more attention => more people seeking solutions to this. I don't have another 50$ to spend on a multimeter... poor student 

[mrkva]

I actually noticed that the front part of construction is actually made in a way it pushes internally on the resistor which was destroyed. Maybe the issue related to that as well?

[retiredcaps]

I actually noticed that the front part of construction is actually made in a way it pushes internally on the resistor which was destroyed. Maybe the issue related to that as well?

It is possible.  The fact that there is no pcb silkscreen designator on both Ut16Cs suggests it is/was a last second bodge on their part.  Otherwise it would say something like R42.

Any word from Uni-T or the seller on a replacement?

[mrkva]

I got no info from UNI-T, but the seller has offered a replacement - for the same model, so I am not exactly happy with that . Actually I can get it to work after few tries of switching to mV range. Sometimes it beeps, sometimes it just jumps around (which is apparently normal when I look at other UNI-T DMM review videos).

[retiredcaps]

Actually I can get it to work after few tries of switching to mV range. Sometimes it beeps, sometimes it just jumps around (which is apparently normal when I look at other UNI-T DMM review videos).

If you short the test leads on the mV range, does the display show 0.0?

[Monkeh]

Beeping and jumping around is normal, it's a 3GOhm input impedance.

[mrkva]

So, wow. It seems like I found a permanent solution 
When I short the leads while changing the range, it doesn't go to the beeping madness!
Would be possible that the voltages without anything connected are in mV range simply jumping too high and sometimes exceed the 600mV limit of the meter?