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| TC1 lcr-meter transistor-tester fix |
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| galaga1982:
Hello madires, I also had an unfortunate incident where TC1 broke down while testing a charged capacitor. To be honest, I knew for the first time that measuring a charged capacitor could damage the device. Anyway, trying to replace zd1 (6V8A) zener diode and dz2 (SRV05-4) diode. dz2 (SRV05-4), SEMTECH is no problem to obtain, but ZD1 (6V8A) was difficult to know the exact PART NUMBER and MAKER As you know, there's a lot of fake online. I would appreciate it if you could let me know the part information you know. Thank you. |
| madires:
Any 6.8V TVS should be fine. |
| shved:
I've blown up another TC1. Needed to replace and reflash AtMega and remove zeners. Now works as usual. Backstory: I have several transistortester models, both store bought and DIY. Pin-outs are different on some of them. I took checked and discharged cap from an vintage amp I was repairing and mistakenly connected it to the zener (AK) terminals, then I've realized my screw-up(as this is the only model with zener mode) and reconnected the cap as it should be connected (123) terminals. Next thing i know - permanent resistors between terminals no mater what.... The moral of the story: Discharge caps before testing! Do not connect anything but zeners and LEDs to KA terminals as this will charge the caps! If cap is big enough both internal and external zeners will not help. The repairs are simple enough, but annoying. Have more than one tester for the job! Hoard test equipment! |
| elecdonia:
--- Quote from: galaga1982 on July 21, 2023, 05:53:01 am ---I also had an unfortunate incident where TC1 broke down while testing a charged capacitor. --- End quote --- I had similar accident with a Transistor Tester. In the original Transistor Tester thread there are discussions about an upgrade with a small relay which totally disconnects the probes from the MCU until the power button is pressed. Additionally, while in the "off" state the relay connects resistors between all 3 probes to discharge capacitors. This is a very reliable protection system as long as one remembers to connect the probes to the capacitor under test while the Transistor Tester is in the "off" state. I intend to add this relay protection mod to the Transistor Tester I use most often on my test bench. (At this point I think I have at least 6 Transistor Testers :-DD) |
| galaga1982:
--- Quote from: elecdonia on July 28, 2023, 08:04:57 pm --- --- Quote from: galaga1982 on July 21, 2023, 05:53:01 am ---I also had an unfortunate incident where TC1 broke down while testing a charged capacitor. --- End quote --- I had similar accident with a Transistor Tester. In the original Transistor Tester thread there are discussions about an upgrade with a small relay which totally disconnects the probes from the MCU until the power button is pressed. Additionally, while in the "off" state the relay connects resistors between all 3 probes to discharge capacitors. This is a very reliable protection system as long as one remembers to connect the probes to the capacitor under test while the Transistor Tester is in the "off" state. I intend to add this relay protection mod to the Transistor Tester I use most often on my test bench. (At this point I think I have at least 6 Transistor Testers :-DD) --- End quote --- Hello? Can you show me a real picture of the relay protection mod you made? I want to make this circuit, too. In my case, even though there were ZD1 and DZ2 diodes, the VCC and GND of ATMEGA324P were damaged by SHORT. I don't want to break the lovely $20 TESTER with CAPACITOR anymore. |
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