Almost Brandnew Uni-T UT116A Unexpectively Is Defect After Hardly Been Used In The Past Years
In the past a brandnew Uni-T tweezer tester, model UT116A, was received with a bad slider switch knob, that immediately got broken and failed after it was tested. And without any warranty from seller or refund from Aliexpress afterwards it needed to be fixed by replacing the from the start bad sliding mini slider switch. Which I successfully did and also mentioned in my repair article in 2023 that can be found here : https://jestineyong.com/fixing-a-defect-but-brand-new-uni-t-tweezer-tester/
Recently I needed to check some smd components on my brother’s 24 year old defect thumble dryer control panel. So I grabbed my previously perfectly working UT116A tweezer tester. But sadly noticed it no longer worked after only producing a short beep when both AAA batteries where inserted.
So I opened the tester to see what ever was wrong with it this time? It turned out that the BAT copper pad was completely gone why the battery spring in the other half of the case no longer made any decent connection. There was no corrosion whatsoever, only a now completely gone BAT- copper pad!
So what I did was fix a new pad with some copper strips from a thin Soldering Tip Cleaning Ball. And that fixed the problem perfectly.
But after that problem was solved my UT116A still had another unexpected problem! Now also the yellow SELECT pushbutton for setting the scan function completely failed working too!
Which was most unexpected to say the least! I examined the board push button side and found nothing wrong with the gold plated contacts of this yellow pushbutton.
I had no service manual or circuit of this tester so I started measuring to what pins of the circuit this button was connected. And found that one side (the bottom pad of the pushbutton pad) was connected to the collector of smd transistor Q3 with marking 1AM, and also to the SEL pin 62 of the ES51926A processor. Which made sense. And the other side of the push button pad was connected to pin 64 of the processor.
The emitter of Q3 was connected to the BAT- pad. The base of Q3 is connected to a resistor with marking 205 and goes through PTC1 and R13 to pin 11 of the processor. This processorpin is the high voltage input for C/R measurements. And pin 66 of the processor was connected to BAT-.
Which was confirmed after finding the datasheet for the 3000 Counts Smart DMM processor ES51926 here => https://www.alldatasheet.com/datasheetpdf/pdf/329818/CYRUSTEK/ES51926.html or here in color => http://www.cyrustek.com.tw/wp-content/uploads/ES51926.pdf These also contain some examples of this processor circuit. Although maybe these datasheets differ from my UT116A processor that ends with the A after its number.
Strangely expecting that replacing this Q3 1AM transistor would solve all my tweezer tester problems, it only solved the Select pushbutton function because afterwards the tester no longer produced any previous working 21V test voltage. And the tweezer input probes now also had a very low impedance and low input test voltage.
Also testing the original now obviously defect removed Q3 transistor in the Peak Atlas DCA75 pro semiconductor tester showed a very strange result saying it was a still working Darlington npn with a hFE of 257? So that tester also was causing concerns about its use to say the least!
Conclusion: I suspect that these UT116A testers suffer from a bad manufacturing process that not only make poorly created copper pads and tracks, but also use transistors that just stop working even after hardly ever been used? My just a couple of times used tweezer tester is no longer worth fixing because apparently also the processor must have stopped working somehow for unknown reasons.
Or maybe it unexpectedly died after it was track traced with my old Metex M-3800 DMM in diode beep test mode? Which could be because of the fact that this about 3V max processor was measured with a DMM that operates on a much higher 9V block battery? (which also may be the fact that processors die like those used in my successful DY294 repair?)
But the reason that these Uni-T tweezers testers are so cheaply sold for just about 21 euro must also be the reason that these testers are so poorly manufactured. They look great on the outside but do fail working unexpectedly in no time!
So let this be a warning to other tweezer tester buyers of the Uni-T testers! I previously liked that they operated on just two AAA batteries, but my trust in their design quality is sadly entirely gone!
My older Mastech MS8911 and DT71 digital tweezer testers still work but are somehow limited when smd components are tested in-circuit. The Mastech needs special CR2450 3V batteries and so is not rechargeable. The DT71 was sold with the promise that it also would show ESR values, but that was in a later update completely cancelled. Also was the new firmware upgrade for this expensive DT71 problematic for other problems like existing calibration issues. And the so praised magnet tweezer arms were not magnetic at all! It was an expensive sold tester without the ESR test, the not working calibration and limiting firmware upgrade.
Recently I therefore bought a Fnirsi LCR-ST2 tweezer tester that was not cheap being about twice the price of my now defect UT116A tester, but definitely is made with very interesting options, like a 1.47 inch bright color HD screen, dual equivalent display mode showing also ESR or Rs of capacitors as also Rp values, and D and Q factor, complete with detachable USB Tweezer arms and Kelvin Clip arms. And it also uses a modern digital selection rotary knob. Fnirsi even added a magnet to the back of the tweezer to be able to easily stick the tweezer to any metal surface. Last month it was immediately easily upgraded to its newest version 1.5 firmware upgrade in just a few seconds. (it was received with still older 1.4 version).
I now have several other of Fnirsi’s fine made products, and they are good made instruments! The only worry I have with them is that they almost all use chargeable lithium batteries. Which may in time be the one part that fails first, and was the nice thing I liked about the portable Uni-T testers that just used plain AAA batteries instead.
Hopefully this article now will prevent other readers from buying apparently inferior measuring tools and from wasting hard-earned money on them!
Albert van Bemmelen, Weert, The Netherlands.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S- If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
Note: You can read his previous article on Brandnew Musical Tesla Coil Already Defect Within 10 Minutes! But Now Fixed and Working Again!
(8)Dislikes
(0)
One Comment
Leave a Reply
Yogesh Panchal
May 16, 2026 at 6:29 pm
Good Fix!Albert,
Very Handy Tool for SMD component testing, I found most of time tweezers tester failure because on PCB components test without discharging surrounding capacitors or forget to select the switch on appropriate Mode.