So I had one of these (a T7) but it just broke and now thinks everything's a zener diode. Any idea where one can get a "good" one - I love the feature set and speed - it was a great tool but yeah I'm annoyed now. Would appreciate any advice.
So I had one of these (a T7) but it just broke and now thinks everything's a zener diode. Any idea where one can get a "good" one - I love the feature set and speed - it was a great tool but yeah I'm annoyed now. Would appreciate any advice.Try this: Connect DC voltmeter to “A” and “K” zener test ports. Minus to “A,” plus to “K.” Then press LCR-T7 “START” button and observe voltmeter. It should read >25V. If <24V then there is a fault in the DC-DC converter circuit which steps up from the battery voltage to the expected 25-30V zener test voltage.
I believe the software checks this “A” to “K” voltage first. If >25V then it concludes “no zener is connected” and moves on to performing the standard transistor tester tests at ports 1,2,3. But if open-circuit voltage from “A” to “K” is <24V then it stays in zener test mode and won’t do anything else.
Also please test several zener diodes, for example 5V, 12V, 15V zeners. Are the results within +/- 1V of the zener’s rated voltage? Also while testing a zener diode: Does the zener get hot after few seconds? (It shouldn’t). If zener gets hot there is definitely a fault in the zener test hardware circuit.
I have three different LCR-x transistor testers with totally different internal circuit designs. Starting in 2022 some Chinese manufacturers substituted <$1 USD MCU chips for the traditional Atmel ATmega328, -324, or -644 MCU ( >$5 USD each and rising ). One of my LCR units with non-Atmel MCU developed the “zener gets hot” fault but otherwise still works OK otherwise.
My units have the following open-circuit voltages from K to A:
LCR-TC2 with Atmel ATmega324 MCU: 25.4V
LCR-TC1 APT32F172K8T6 MCU: 30.2V
LCR-TC2 LGT8F328P MCU: 25.2V
Note: The Chinese manufacturers interchangeably label their models as LCR-T7, LCR-TC1, or LCR-TC2.The only way to identify “what is inside the plastic box” is from a photo of the PC board. However the vendors don’t provide photos of the PC boards.
While I appreciate the thought a diode sort of burned itself in two and it's next to some very unhealthy looking components, I accidentally scraped the diode off trying to clean it up a bit and see what it was and yeah it's bad...
No idea why this happened either, I've been treating it right!
I have just received a "TC1" of this latest design elecdonia. Within a couple of days it failed while testing a few zeners and schottky diodes on the K-A terminals. After the failure it would always show a 4.1V zener across the K-A terminals and when I opened the box it was obvious that D2 was burned.
I was able to find a replacement SMD diode for D2 and it was soon working again but I noticed whenever I tested a zener diode both the zener and D2 would get very hot. Apparently there is nothing to limit the current through D2 and the tested device other than the ability of the DC-DC converter circuit to supply current!
I found a solution on another site (that I now can't find) that suggested cutting the track between C14 and the K terminal and inserting a 4K7 resistor.
this manufacturer substituted a “step-up constant-current LED driver” IC.
In case of a genuine ATmega you can try an OSHW firmware and run the selft-test to check the test pins.
Just bought a tester marked Multi-function Tester - TC1 from ebay. It is never able to test any component but it does boot up ok and the display is ok. It doesn't recognise any components in the 1,2,3 sockets, it just displays "unknown or damaged part" after pressing the start button.
If I put a diode in the (K, A) part of the socket it does recognise it as a zener, so it seems to be stuck in zener mode.
It has a blue PCB with no transformer, uploaded a photo.
Yes I tried the self test and just got the “unknown or damaged part” message. After pressing Start testing across the 1,2,3 pins gives 0 volts. testing across K,A gives 25.4v. Do you know what voltage I should get across the 1,2,3 pins after pressing the start button?
Thinking that there could be a bad connection to the test pins somewhere, might try working my way back re-soldering the joints.
…other than this thinking the 6 pin V05 (D2) might need swapping.
Yes, if I press the Start button for around 30 seconds the language does change to Chinese.
To conclude, the fix is:
1) Cut the PC board foil leading to pin K and then connect 2K2 resistor from junction of D2 and C14 to pin K,
2) Replace U7
...
I don't know what chip U7 is but looking at your board D2 shows no sign of burning or heat. If you still measure 28-32V on the K-A pins with no component connected then U7 is still working and all you need to do is to cut the track between C14 and the K terminal and insert a 2K2 resistor. Once this change has been made this version of the tester seems to work well.
Before asking the question I tried reading the discussions to find an answer, but without success. The search system could not find a suitable post for me according to the parameters I had.