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TC1 lcr-meter transistor-tester fix

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madires:
You could buy a new TC-1 and add a switch for the LiPo. If you're looking for alternatives check out the AY-AT clones, e.g. GM328A, and the Hiland M644. And if you program one of the two OSHW firmwares you'll get even more features. BTW, there are two mods for the TC-1 to make it compatible with the OSHW firmwares. The hardware mod also reduces the quiescent current to a few µA.

Feliciano:
If you easily find the spare parts you can try to fix the one you have, following the tips on the previous 5 pages (in most cases to replace the protection diodes ZD1 and/or ZD2 if you forgot to discharge a capacitor, as well as some caps that tend to leak or go short because the close to 40V on the Vz section of this device). If you end replacing the MCU, remember to reprogram or replace U4 with the alternative circuit (two transistors plus some resistors and diodes) before attempting to flash m-firmware or k-firmware.

Or because these ttesters are inexpensive, you can buy the one that better suits your particular needs. Here, the main models at a glance: https://github.com/madires/Transistortester-Warehouse/blob/master/Documentation/English/Clone-Comparison-Chart.pdf

Felipe Lacerda:

--- Quote from: Feliciano on August 27, 2021, 01:10:47 pm ---you can buy the one that better suits your particular needs. Here, the main models at a glance: https://github.com/madires/Transistortester-Warehouse/blob/master/Documentation/English/Clone-Comparison-Chart.pdf

--- End quote ---

TC1 needs the mod to accept opensource firmware... does T7-H need it too? what is the best choice?
According to the table are the models that support upgrade to the 644.

*I want to buy a new one, but I haven't found any on Aliexpress already with the 644.

F1RVC:
Hi, does  somebody already had  on a TC1 (M-tester V2.12k) a Zener value displayed always (with no  component connected) at the startup?. All other functions look to be ok, if  I put other kind of component , it is ok, but  with no component it detect a  zener and with a zener the measure is bad.
I checked 37v (approx) is here, the zener voltage  is going to PA4 thru a divider by 10, Should have  3,7v  here but  input look to be pulled down by PA4 and the low voltage is displayed like a zener voltage. Also the Ref voltage  2.5V (TL431)  is also pulled down to 0V on PA3 by the 324PA, if I isolate PA3 the ref voltage rise up to 2,5V.  If I isolate the PA4 , it also diplay a zener voltage at startup  with  0V value !
I do not tremember having done a bad measure with non discharged component , TC1 did it by itself one day at the bootup.

Before trying to change the ATMEGA with a new one and flash it with the original TC1 firmware provided on this  thread, maybe I missed  something more easy to fix  this TC1?
Any advice or clue will be apreciated.
If  I start in this  way , I will probaly tweak  it with alternative k firmware  and hardware U4 mod later (but before I would like to fix it ) ...

madires:
PA3 and PA4 should be in HiZ mode. If both suddenly short the input to ground then they most likely let the magic smoke out.

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