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TC1 lcr-meter transistor-tester fix

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shved:
Thanks madires.
I think I've fixed it. Now the stand-by current is around 0.2mA.
The problem was in the caps C6 & C7. The caps turned in to resistors and loaded the battery and 5V rail through the diodes. I don't quite know where the energy went, the caps didn't heat-up. I've tracked them down because 5V rail read too low(~4,5V) and battery check on boot showed the wrong voltage. To isolate the issue I've disconnected the diodes in turns, when 5V came back clean, I knew immediately to check the caps!
Also, the factory where they assemble the bloody things uses some reactive flux and doesn't clean it off. I strongly suspect that it's a factor, seen that before.

Anyway, anyone who has excessive stand-by current(around 20mA) check the caps C6 and C7! And I advise to wash the flux off the boards.

a_kiler:
Hi, everyone.

Like most of us here I unfortunately damaged my brand new T7-H. Capacitor dead screen... sounds familiar?   ;)

Thx to advice:
@zappenduster: I bought 10uF capacitor; (didn't use it)
@indman: I removed DZ1 and DZ2 and... success, the screen is on. But sth else strange (for me) happend.
Tester works "like new".

Calibration: pass
Capacitor: pass
LED: pass
IR: pass
Even removed DZ2 - zener diode: pass

So if DZ2 is ok, DZ1 must be failure.

Oh, BTW - my is tester is a little bit different (pictures included) and DZ2 is 6V8C, DZ1 is V5L. I hope datasheet ic correct?

How can I examine DZ1?

@zappenduster said earlier:

--- Quote ---ZD1 = zener-diode 6V8 ; DZ2 6-pin marked V05. Some pcb miss those two elements - maybe earlier layouts...
--- End quote ---

Is it possible the tester will work normally without DZ1 DZ2 or should I expect the unexpected.

madires:
Yep, the tester works also fine without the input protection (DZ1 and DZ2). DZ1 should be a 6.8V TVS (not shorted = OK).

belzrebuth:
I did the charged capacitor trick on mine so now it's dead..
DZ2 is certainly faulty and I've also found some shorted ceramics in there as well.
In total I've removed capacitors C14,C15,C24,C21,C23.
I haven't yet measured DZ1 but I've removed it for good measure.

I've also tested the 5V regulator out of circuit and it's working.

The problem is that the meter only boots when I'm applying 5V externally in the place of the 5V reg output.
When it boots it shows there's a DC source between terminal 2 and 3.
When connected to a USB plug only the red charging LED lights up but the meter is dead.

I think I'm probably having a problem with other stuff as well like the DC-DC section or else.

Since the MCU is probably working what might be going on with the power stuff?
How did I manage to save the MCU and I have a problem in the PSU section.
There is no input voltage to the 5V regulator when I'm connecting the USB plug so no wonder the meter is dead.

What could be the culprit here?
Would it be fixable?

madires:
Presumably the ATmega's pins used for terminals #2 and #3 are shot and maybe also the control MCU U4. You can check the DC/DC converter by enabling it manually.

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