Products > Test Equipment
TC1 lcr-meter transistor-tester fix
Kamlakkannan:
And now again just a white screen
alfagulf:
I would like to add my experience with the TC1 that I bought from Banggood as a replacement for another unit which I zapped by connecting a charged high voltage capacitor by mistake |O.
The new unit arrived faulty. >:(
The unit did not power up, so I assumed the battery is dead and need to be recharged, which I did, but still pressing the start button did nothing.
I contacted them and they offered a refund which I accepted.
However I suspected the problem is around U4 (STC15W104) since it manages the start button and sends a signal to the boost converter U5 to start.
I noticed that pin 3 (P3.5) is not going HIGH when I press the button which of course the reason why it is not powering up.
I first reprogrammed U4 with the alternative firmware https://github.com/atar-axis/tc1-u4 , but that did not change any thing.
I then replaced U4 with the one I had in my first faulty unit. I started to have some intermittent success where the unit will power up sometimes and shuts down unexpectedly.
I then did more testing around the push button when I noticed C13 a debounce capacitor that had its resistance rather low (around 30K).
I removed it and the tester worked like a charm.
However I then replaced it with a good 100nF capacitor to keep the debounce function.
The U4 which I remove (I suspected to be faulty) turned out not faulty, I found out that by reprogramming it to output a 1Hz pulse on all ports which it did.
So I guess the problem for me was the faulty ceramic C13 capacitor. :)
I hope this information might help some of you.
Thanks
dvd4me:
Hello,
I just got today the TC1 from Bangood and it was defective, not turning on.
I found this post and after measuring the caps on the battery or the +3.7V rail, nothing wrong.
Plugging the battery made the screen to briefly turn on.
At the power on button, I noticed there was no voltage on the button contacts, just a very low 0.3V.
Putting 5V at the output of the U3 regulator made the screen to turn on but the boot stops at the daniu logo.
I just saw the post before me and noticed the C13 warning it might be leaky.
Removed the C13 and now it powers up at the insertion of the battery, yey!
Measuring the voltage at the power button is 3.8V ! So that's the normal voltage it should be on a normal tester.
I just put the cover back and that's it for now.
Now it works, see the second picture.
shved:
A friend gave me TC1 with bulged battery and some damage.
I've cleaned it up and swapped in used samsung mobile phone battery. Changed c13 as a precaution. Everything works, as far as i can check. But stand by draw is around 20mA. Is that normal? Do i need to add a a battery cutoff switch? I have several LC, RLC, ESR, ... meters, but with external power(no battery only USB or 12v PSU), so i plan to use it for away jobs witch are quite infrequent.
My point is: the tester will be always "flat" when i grab it.
Any advise?
madires:
That stand-by current is much too high. A classic power switch would be a simple fix. If you want to run one of the OSHW firmwares (k or m-firmware) you can replace U4 with a small circuit with two BJTs and the stand-by current will be about 5µA. With U4 the current should be around 0.2mA.
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