$20 LCR ESR Transistor checker project

[py-bb]

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 bet you have the same (very poorly designed) LCR-Txx model that I received a couple of months ago. Does the area where the PC board has bad (cooked) components look like the attached photo? And is the toasted diode labeled D2?

Sorry for late reply, you're exactly right it's that bit. My diode was far more visibly cooked though it'd basically popped in half.

Any recommendations on getting a long and happy life out of the replacements? I apologise you clearly know a lot about the model and I regret treating mine as screwed (I used it for heatgun practice)

[elecdonia]

The short could be under the ZIF or the 6 pinV05, or a damaged MCU, at least the infra red remote test works ok.  lol.

Check very closely for solder bridges at all locations where the PC board foils for test socket terminals 2 and 3 connect to the MCU, to the V05 protection device, and to the group of 680R and 470K resistors. You will need a microscope or a strong magnifier. These pins 2 and 3 connect straight to 2 pins on the MCU which may be right next to each other. Even if you don’t find a visible solder bridge it is a good idea to reheat these IC pins after applying solder flux to them. The solder flux is the important part: Flux permits solder bridges to separate when the solder melts. If you find a big blob of solder anywhere then use desoldering wick to absorb the excess. I recently learned to add additional solder flux to the desoldering wick before using it. Even though the wick already contains flux, “everything works better with extra flux” when correcting solder bridges.

If there aren’t any solder bridges then I suggest removing the V05 protection IC as the next step. Although V05 is rated at 10A peak current it isn’t totally bulletproof. It is safe to operate the transistor tester with V05 removed as long as you are careful to discharge capacitors before testing them. If V05 is the culprit then get another one and replace it before using the tester heavily. I have a tester where V05 did fail. Everything worked again after removing the faulty V05. It sacrificed itself to save the MCU.

A short underneath or inside the ZIF test socket is unlikely but if nothing else clears the short between pins 2 and 3 then I recommend desoldering and removing the ZIF socket. There is a first time for every failure.

Here’s the most important thing: Your transistor tester has a direct short between ZIF pins 2 and 3. But this isn’t a short to ground or +5V is it(please confirm)? When an IC fails it will often have pins shorted to ground or VCC (+5V in this case). It isn’t likely for 2 pins of an IC to short to each other without also being shorted to ground or VCC.

Summary: If the only short in your unit is between pin 2 and pin 3 this means there are only a small number of causes for this fault.

[elecdonia]

Any recommendations on getting a long and happy life out of the replacements? I apologise you clearly know a lot about the model and I regret treating mine as screwed (I used it for heatgun practice)

Replace diode D2 and step-up IC U7. Add a 2K2 series resistor between the junction of D2/C14 and the K pin of the ZIF socket. This requires cutting the PC board foil between these two points. Doing this will make the zener testing circuit unbreakable.

It’s a pity the manufacturer neglected to include the 2K2 series resistor.

[elecdonia]

Put the scope on the 1,2,3 pins, after pressing start I get a short series of pulses at 5 volts, except between pins 2 and 3 where I get 0 volts.

Are pins 2 and 3 both shorted to ground?

[alex_D]

Sorry yes, pins 2 and 3 are shorted to ground, so likely no short under the ZIF.

I guess that likely means V05 is bad?

[Feliciano]

I guess that likely means V05 is bad?

Maybe. You can remove it and mesure again.

[elecdonia]

Sorry yes, pins 2 and 3 are shorted to ground, so likely no short under the ZIF. I guess that likely means V05 is bad?

It is very likely that V05 failed. Try removing it.

[alex_D]

Removed V05, but the short still exists, it must be a defective MCU, reached the end of the road with this clone box.
Anyway I've got a AY-AT kit on the way with loads more options, so no loss 

[Feliciano]

A final test you can do: cut a trace and measure the ports directly.

And you can save the protection IC for future use.

[elecdonia]

Removed V05, but the short still exists, it must be a defective MCU, reached the end of the road with this clone box. Anyway I've got a AY-AT kit on the way with loads more options, so no loss 

I recently bought an AY-AT kit. For years I’ve had a factory-built AY-AT. It has served me well. In fact it is getting a bit shabby from years of daily use.

Because these AY-AT kits are so cheap ($10-12 USD) I decided to get one. I’ve assembled my AY-AT kit and am beginning to test it.

In addition I fired up my MCU programming kit in order to try out different TransistorTester firmwares. My programming device is an Arduino UNO loaded with the standard “Arduino as ISP” sketch. I recently obtained a nifty programming shield for it which has a ZIF socket. Another cool item I just started using is the superb AVRDUDESS GUI front-end app for AVRDUDE. Wow! It makes programming chores much faster and easier!

At this time my two AY-AT units are still running their original Asian factory firmware. Both are a modified 1.12k. Each is slightly different. The older unit has fewer items in the user menu compared to my new AY-AT kit. Unfortunately the MCU flash is locked in my older unit so I won’t be able to directly compare flash contents. However the ATmega328P which came with my new AY-AT kit is unlocked. I’ve already grabbed the contents of its flash and EEPROM.

My next task is to get both of them to run the 1.13k firmware. I have a whole tube of brand-new ATmega328P. Both of my AY-AT units have a socket for the MCU, making it very easy to swap different firmwares.

[alex_D]

A final test you can do: cut a trace and measure the ports directly.

Yes I did cut the trace next to the MCU at pin 24, I can confirm 100% the short is at the MCU.

Is it worth swapping out the MCU for a real ATMega? probably not. would it work with this clone board?
then I would need to program the replacement with the open source firmware, I'll keep the box in case I try to give it a go. 

[alex_D]

Removed V05, but the short still exists, it must be a defective MCU, reached the end of the road with this clone box. Anyway I've got a AY-AT kit on the way with loads more options, so no loss 

I recently bought an AY-AT kit. For years I’ve had a factory-built AY-AT. It has served me well. In fact it is getting a bit shabby from years of daily use.

Because these AY-AT kits are so cheap ($10-12 USD) I decided to get one. I’ve assembled my AY-AT kit and am beginning to test it.

AY-AT kit looks like a good choice then. I noticed there are a few upgrades you can do like swapping out the crystal, and upgrading the voltage regulator.

[Feliciano]

Is it worth swapping out the MCU for a real ATMega? probably not. would it work with this clone board?
then I would need to program the replacement with the open source firmware, I'll keep the box in case I try to give it a go. 

As elecdonia recently mentioned, there are at least 3 kinds of alternate MCUs for this series of ctester. If you modify the pinout for a valid ATmega, you could swap the damaged MCU, but you would also need to replace the power controller MCU with a circuit previously described in this thread, and program the new ATmega with the m-firmware. Would it worth it? For me, if the options were throw it away, or rescue it for few pounds, I would proceed and later rejoice.

[indman]

As elecdonia recently mentioned, there are at least 3 kinds of MCU for this series of ctester. If the pinout is valid for ATmega, you could swap the damaged MCU, but you would also need to replace the power controller MCU with a circuit previously described in this thread, and program the new ATmega with the m-firmware.

This is not the case, you are slightly mistaken here.I do not see any difficulties and obstacles in order to bring this clone back to life and normal operation. LGT8F328 is 99% similar to ATmega328 in terms of the location of contacts. Therefore, here is the procedure that should be done:
1. Remove the old controller from the board.
2.Before installing ATmega328, carefully compare those contacts that are designed for normal ATMEL operation and activate them.This applies to pins 3,6,18,21
3.Compile a new firmware for ATmega328.This is perhaps the most difficult point for beginners, but also realizable.

[indman]

Madires,as you know, now it is impossible to say with 100% certainty that the clones of the LCR-TC series can be upgraded, as there may be "surprises" from Chinese friends inside the package.

Here is 1 more version of the LCR-T4 "surprise" from Chinese friends on LGT8F328. However, it can also easily be redesigned to work with genuine ATMEL. It remains only to purchase a few spare ATmega328 from the same Chinese friends!

[Feliciano]

2.Before installing ATmega328, carefully compare those contacts that are designed for normal ATMEL operation and activate them.This applies to contacts 3,18,21

indman, thanks for bringing this to my attention, but I think you forgot the pin 6.

[indman]

but I think you forgot the pin 6.

Yes, thanks you for noticing.I have apdate my post above. 

[cincin]

I read a half-dozen pages back but couldn't find a clear answer: Where can one reliably purchase one of the better one of these nowadays?

From what I read back in this thread, the good ones are not sold anymore, or are hard to find old-stock, and there's a million lesser clones being sold as the good ones everywhere. Is that correct?

So there are no known reliable sources for decent ones? I'm probably not looking to tinker with it much (may not need to be flashable if it's already useful), just to use it for part ID and tester.

Cheers!

[elecdonia]

I read a half-dozen pages back but couldn't find a clear answer: Where can one reliably purchase one of the better one of these nowadays?

I recently purchased this LCR-TC2 unit:
     https://www.ebay.com/itm/LCR-TC2-Transistor-Tester-Diode-Triode-Capacitance-Meter-V2-3E-with-Tester-Cable/295395097022/

After inspecting it internally and using it for several weeks I confirmed it contains the desirable ATmega324P MCU. Its performance and accuracy are very good. The zener test feature works properly without overheating the zener diode being tested. The internal rechargeable lithium cell provides plenty of hours of use. In fact I haven’t needed to charge it yet.

Notes:
1) This unit has a dark blue front panel with manufacturer’s logo at top left (2 Chinese characters).
2) Model number is “LCR-TC2”
3) Version is “V2.3E”
4) The ebay listing contains a color image of a detailed user manual provided by the manufacturer. My unit arrived with a printed user manual identical to what was shown in the ebay listing.

I should mention that several months ago I acquired two other LCR- units which contained alternative (non-Atmel) MCU. Both had issues and faults. In my opinion they were barely functional. Those units had light gray front panels without any manufacturer’s logo. The ebay descriptions did not show the color image of the manufacturer’s user guide.

Conclusion: I do not recommend purchasing any LCR- unit other than this LCR-TC2 V2.3E unit with the dark blue front panel which carries the manufacturer’s Chinese logo.

[cincin]

Thanks! Unfortunately, that seller doesn't ship to Canada. But I will try to find that specific unit somewhere else. If anyone has a reputable lead that ships to Canada, please do tell.
Cheers!

[elecdonia]

Thanks! Unfortunately, that seller doesn't ship to Canada. But I will try to find that specific unit somewhere else. If anyone has a reputable lead that ships to Canada, please do tell.Cheers!

The ebay vendor I ordered my LCR-TC2 V2.3 unit from ships to USA locations from a warehouse inside the USA. That might be why they don't ship to Canada.

I know of several other Chinese ebay vendors who offer the exact same LCR-TC2 V2.3E unit. I've ordered from ebay vendors listed below. They have nearly always shipped what I expected. If there was any issue they immediately issued refunds.

     alice1101983 (557,445) 99.7%
     worldchips (181,380) 99.6%
     modulefans (109,038) 99.4%
     diybox (73,854) 99.4%

Another thing I noticed is most ebay listings for this version of the Transistor Tester include all of the following words in the listing title:

           high precision LCR-TC2 V2.3E

Therefore I recommend using the above words for searching on ebay

[MrSqueaky]

I read a half-dozen pages back but couldn't find a clear answer: Where can one reliably purchase one of the better one of these nowadays?

I bought an LCR-TC2 back in December from Aliexpress https://www.aliexpress.com/item/1005004717377243.html.

It contained an ATmega324 and has worked well so far https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg4635052/#msg4635052

[ws786873]

I bought an AY-AT clone and bought the resistor and IC needed for the upgrade. But when I wanted to burn the M firmware, I found that I could not find the pre-compiled firmware that could be burned in the Windows system... It seems that it needs to be compiled and burned on the Linux system... Can anyone provide the pre-compiled M firmware? I used 16MHZ crystal oscillator.

[py-bb]

Any recommendations on getting a long and happy life out of the replacements? I apologise you clearly know a lot about the model and I regret treating mine as screwed (I used it for heatgun practice)

Replace diode D2 and step-up IC U7. Add a 2K2 series resistor between the junction of D2/C14 and the K pin of the ZIF socket. This requires cutting the PC board foil between these two points. Doing this will make the zener testing circuit unbreakable.

It’s a pity the manufacturer neglected to include the 2K2 series resistor.

Hi there, I've ordered 2 replacements as unfortunately being without this bit of tat sucks. Before I do the mods any recommendations? I have some diodes I need to test - should I be really careful in which way around they go?

I appreciate your advice on this as you clearly know a lot about these devices. Would you like to hear back if I do the mods?

Thanks

[GraemeG]

Assuming you have that particular version of the tester, my advice is DO NOT test anything on the zener test pins (K - A) until you have made the mods. You might get away with it if it is a higher voltage zener and you are fast but there is a good chance you will burn D2 and possibly damage the DC-DC boost IC.

I didn't have any SMD resistors of the right value but it is not too difficult to use a normal through-hole resistor. Cut the track near to the K pin and carefully scrape the copper clean on the track leading to D2. With the resistor lying flat on the board near the end of the ZIF sock pins, solder one lead of the resistor to the K pin (easy) then carefully adjust the other lead to align with the cleaned track. It shouldn't be too difficult to solder the lead to the track if you have a reasonably fine soldering iron tip.