$20 LCR ESR Transistor checker project

[Feliciano]

I think the failure is located around the boost converter (lC marking B628), because if I somehow alter a little its Q point, it works. In fact I re-centered the output capacitor, and cleaned beneath U6 and some resilient goo around L1 and it has been working for a few hours. Fingers crossed.

[madires]

Heating up the MLCC could have fixed the issue.

[Feliciano]

It could be, because this time I heated it a lot (and even rolled it over). I keep watching it.

Anyways, I was about to ask you:

a nearly shorted MLCC.

IIUC, you're describing that some layers can be shorted or compromised? If that's the case, it should measure a lower capacity and/or high ESR, and/or high Ileak and/or high Vloss, right?. I didn't notice some really bad values of it (from k-firmware), but without knowing the nominal value for my transformerless variant, I'm not sure. Still, how come when it had some vapour/liquid residues nearby it worked?

[madires]

MLCCs can fail in different ways. One is a dead short, and another is a low resistance (a few or 10s of Ohms). And there's also some humidity issue which can sometimes be resolved by simply heating up the cap. I have no idea why the alcohol helped temporarily.

[YouCanDoIt]

Hello to all guys,
I just joined the forum after spending a good amount of time in researches without coming up to a solution.
From what I have understood, as of now a device with an ATMega644/ATMega1284 and higher is the most desiderable because allows higher accuracy and many more features.
Hovewer, in the clone comparison chart I only see Hiland M644 which is limited to ATMega644. Very hard to find and sold at $40 in a couple of places. Some web pages before this one, an user said that it is just a waste of money which makes me think there would not be any significant difference between the old versions.
The list also shows some "LCR-T** marked as "possible ATMega644". I suppose the situation would be even worse for such models.

What seems to be very amazing is the Mega-4GSL, but I have not been able to find any DIY kit anywhere. Did someone here in the forum tried to build one? Where to find all the needed parts? I have no idea on the costs, but if there are other interested users we could create a purchase group and help each other in the build process.

Apart from this, are there any other alternatives?

[Feliciano]

Welcome to the forum.

Currently it's not easy to find an original ATmega unit (I guess politics and economics reasons). Therefore you can buy any and use it with it's original Chinese firmware (keep in mind the fancier the interface, the less functionality). Or you can keep looking for an original one, being able to flash the OSHW firmware discussed on this long thread, where you can select a set of the most important functions to your liking. Note: If you buy a DIP version, you have better chance of getting a real 328.

Or as you said, you can build one yourself (with an 644 or 1284, for reacher fetures set), alone, or along with some other European readers.

[jdev99]

Just received this one, with original ATmega328P. They are still out there. 

https://www.aliexpress.com/item/1005005497252414.html?spm=a2g0o.order_list.order_list_main.5.52321802KA7hcS

[YouCanDoIt]

Currently it's not easy to find an original ATmega unit (I guess political and economic reasons). Therefore you can buy any and use it with it's original Chinese firmware (keep in mind the fancier the interface, the less functionality). Or you can keep looking for an original one, being able to flash the OSHW firmware discussed on this long thread, where you can select a set of the most important functions to your liking. Note: If you buy a DIP version, you have better chance of getting a real 328.

Many thanks for your help. I was originally planning to buy "M328Kit+TFT(AY-AT)" I saw on the chart since this one seemed to be the best one. Is right? Please accept my apologies for the stupid questions, but I am totally newbie about transistor testers. This model seems to be non DIP and therefore should be easier to find a genuine version, but what is the difference between DIP and non DIP versions?
There is still the problem that an ATMega328 can't run a full feature firmware and its low accuracy. Given the low price of the controller, I am wondering if I could just replace the bundled ATMega328 with an ATMega1284 and flash it with the related firmware.

Or as you said, you can build one yourself (with an 644 or 1284), alone, or along with some other readers.

Yes, this is the option that I'm currently evaluating, but it's getting harder than I thought due to the lack of sources. I thought to the Mega 4gsl because it has been mentioned here, but I should first try to understand how it really performs to see if it's worth all the efforts to build one.

I'm also unable to estimate costs. There are 150 components. By a quick (and dirty) look up it should be around 15-20$ for the board components, $5-15 for LCD+battery (depending from what can be adapted). It should remain the PCB and the case, but I have not been able to find these anywhere. The user pizzigri posted here what he spent to build one and I got totally shocked to see it was 140 € (euro). Hope it has been a typo.

If someone can post some documentation source I would really appreciate. The PCB photo shows a non existent link to https://www.mikrocontroller.net/svnbrowser/transistortester/ and I'm wondering if this is a dead project. The firmware is heavily customized and I have read somewhere it is private. I am concerned about updates given the fact that the official ones regularly published will not work for sure.

Just received this one, with original ATmega328P. They are still out there...

Many thanks for the link. It seems to be a version of the GM328A different from the ones showed in the comparison chart. Isn't "M328Kit+TFT(AY-AT)" a better choice?

[YouCanDoIt]

I forgot to mention that I have also considered smart tweezers given the fact that now prices are more accessible. For example I saw here in the forum DT71 and although I have read many good reviews on the web, the one posted here is not good at all:
https://www.eevblog.com/forum/blog/eevblog-1335-miniware-$70-dt71-lcr-tweezer-review
That topic was around 3 years ago, so may be they managed to improve the quality through firmware and/or hardware changes.
I suppose that in the meanwhile new models entered in the market, but I'm not an expert and I have not gone further.

What I would like to know is that, for such price range, smart tweezers could be a better replacement of any of the best testers discussed on this topic.

[Feliciano]

If you buy a DIP version, you have better chance of getting a real 328.

but what is the difference between DIP and non DIP versions?

(Besides one being rectangular and larger whereas the other square and smaller), as we have been discussing on this thread, it seems the knock-off MCUs are being manufactured on small square encapsulations (cheaper), so that's why some of us think if you look for a DIP28 ATmega328P-PU, and if the vendor photo it's accurate, you have chances of obtaining a read one (with 32KB of flash, of course).

There is still the problem that an ATMega328 can't run a full feature firmware and its low accuracy. Given the low price of the controller, I am wondering if I could just replace the bundled ATMega328 with an ATMega1284 and flash it with the related firmware.

If you have a real ATmega, you can evaluate what changes you could make. Or, if you have an LGT8F328P-based unit, and you have a real ATmega, you could adjust the pinout and make the replacement.

If someone can post some documentation source I would really appreciate. The PCB photo shows a non existent link to https://www.mikrocontroller.net/svnbrowser/transistortester/ and I'm wondering if this is a dead project. The firmware is heavily customized and I have read somewhere it is private. I am concerned about updates given the fact that the official ones regularly published will not work for sure.

kubi48, madires, and indman have posted documentation on different sites. madires has gathered many of that  (including an overview I composed) at github.

[rfink07]

Hi, first time posting here. Let me know if there is a better place to ask this.

I bought a variant of this product recently, mostly to measure transistor gain. I've measured several 2n3094 and 2n3096 components, and they all measure hFE ~ 370. If I'm reading the datasheets right, it shouldn't exceed 300 (and usually be much lower).
https://www.amazon.com/Mega328-Digital-Transistor-Resistance-Capacitance/dp/B07WT9VVZB#customerReviews

Am I missing something? I saw that there can be measurement errors for leaky parts (germanium), but haven't seen complaints about common Si parts.

[rsjsouza]

Assuming the transistors are legit, historically the hfe alone is a parameter that has a wide variability across manufacturers and even within the same manufacturer or the same batch. Also, it is highly dependent on the bias applied to the transistor.

I wouldn't rely much on it, unless you are talking variations of orders of magnitude...

[rfink07]

Thanks - the main reason I am confused is I measured ~10 components and they are remarkably consistent, all between 360-380, which differs from the datasheet

[indman]

I bought a variant of this product recently, mostly to measure transistor gain. I've measured several 2n3094 and 2n3096 components, and they all measure hFE ~ 370. If I'm reading the datasheets right, it shouldn't exceed 300 (and usually be much lower).
https://www.amazon.com/Mega328-Digital-Transistor-Resistance-Capacitance/dp/B07WT9VVZB#customerReviews
Am I missing something? I saw that there can be measurement errors for leaky parts (germanium), but haven't seen complaints about common Si parts.

You must clear understand that ONLY the original autors firmware installed on the device can to a greater extent guarantee the reliability of the results when measuring transistor parameters. And this is provided that the hardware of the tester is in good working order, the supply voltage of the microcontroller is well stabilized and clean. If your tester has original Chinese firmware installed, no one will give you any guarantees regarding the correctness of the results of testing various parts.

[YouCanDoIt]

If you buy a DIP version, you have better chance of getting a real 328.

but what is the difference between DIP and non DIP versions?

(Besides one being rectangular and larger whereas the other square and smaller), as we have been discussing on this thread, it seems the knock-off MCUs are being manufactured on small square encapsulations (cheaper), so that's why some of us think if you look for a DIP28 ATmega328P-PU, and if the vendor photo it's accurate, you have chances of obtaining a read one (with 32KB of flash, of course).

There is still the problem that an ATMega328 can't run a full feature firmware and its low accuracy. Given the low price of the controller, I am wondering if I could just replace the bundled ATMega328 with an ATMega1284 and flash it with the related firmware.

If you have a real ATmega, you can evaluate what changes you could make. Or, if you have an LGT8F328P-based unit, and you have a real ATmega, you could adjust the pinout and make the replacement.

Many thanks for your help. I will ensure to follow these guidelines if I will end up with a clone. I will post the parts I found and I would appreciate if you could ensure I will not do mistakes.

If someone can post some documentation source I would really appreciate. The PCB photo shows a non existent link to https://www.mikrocontroller.net/svnbrowser/transistortester/ and I'm wondering if this is a dead project. The firmware is heavily customized and I have read somewhere it is private. I am concerned about updates given the fact that the official ones regularly published will not work for sure.

kubi48, madires, and indman have posted documentation on different sites. madires has gathered many of that  (including an overview I composed) at github.

Thanks, the link helped me a lot. I have read all the stuff included the faqs and now I have a better idea on how things work. However, even after having followed all the links available in github and its pdf files, unfortunately I didn't found anything about Mega 4gsl.

[rfink07]

Update: I made a simple voltage measurement circuit for the transistors and it read... exactly the same as the meter.

[Feliciano]

Many thanks for your help. I will ensure to follow these guidelines if I will end up with a clone.

Thanks, the link helped me a lot. I have read all the stuff included the faqs and now I have a better idea on how things work.

Welcome, and please note there's a "Say thanks" button on the forum 

[Feliciano]

I've updated my FAQs. Attached.

[YouCanDoIt]

Many thanks for the updated Faq!
In the spirit of sharing I post a link where is possible to buy the parts for the MEGA 4GSL. Prices are good and should be available as DIY kit or professionally assembled. Revision should be the latest (2022) while the one I saw posted in the topic is 2015.

I am in doubt if I should go with a Mega 4GSL or an Hiland M644 (which I will customize with all the possible mods I can find here in the forum including the MCU replacement). Do you think they are at the same level or a Mega 4Gsl is still far better even than a modded M644?
What you would buy if you were me?

[Feliciano]

Continuing with my WIP clone, I found a major issue with one of the latest m324pa transformerless TC1 clones, limiting the OSHW mod posibilities: the manufacturer modified the push button behaviour so is no longer directly connected to the STC, but between two(three) transistors, where the power_lock is no longer triggered by the STC but from the ATmega itself (pin16 high on my m324pa), and the push button sends a low on pin42 of my m324pa. Therefore, the known "two vanilla transistors mod" to flash OSHW firmware is no longer valid for this model.

I attach a [WIP] diagram looking similar to the unit on my benchtop.

So what do we do now: create a new circuit for U8(STC) substitution, and/or create a new variant of the m-firmware config for this case? (I can test either).

In any case, a friendly warning for other Users until this is solved: please check what ATmega TC1 clone variant you have before attempting to flash the OSHW firmware.

[indman]

Feliciano, you have become the “lucky” owner of another FNIRSI product, congratulations!
The engineers of this company seem to have set the task of making a product that does not lend itself to such a simple upgrade to the original transistor tester design.
However, this remark applies to all FNIRSI products - for the most part, hastily put together low-quality products with the goal of getting the maximum benefit from the sale as quickly as possible and then forgetting about support and eliminating errors for the consumer.

My thoughts on finalizing this miracle of Chinese thought:
1. Remove STC and forget about it!
2. Try to improve the circuit using this option, which I showed below.
3. Check the assignment of the display contacts to the microcontroller, as they may also differ from the standard ones.
4. Of course, you will need to adapt the autors' firmware for this clone, since cutting the tracks and laying new conductors will be ugly.
But, if desired, this option can be implemented. Although, to be honest, I wouldn’t waste my time on this.

[carl1961]

GM328A up and running on 1.13k   Non removable MCU
Files I changed attached
mega328_color_kit Makefile and lcd_defines.h  This display is mounted the opposite of other older GM328A I had to reverse the settings in lcd_defines.h

How I did it I put on GitHub
https://github.com/carl1961/New-GM328A

[indman]

carl1961, What frequency is the quartz currently set to?
1.13k is set to 8 MHz, and 1.51m is set to 16 MHz. Does this tester work stably at 16MHz?
And one more note - during measurements, tests and work with the device, no conductors should be connected to the ICSP bus! This can greatly ruin calibration and test results.

[Feliciano]

Feliciano, you have become the “lucky” owner of another FNIRSI product, congratulations!

to be honest, I wouldn’t waste my time on this.

indman, I respect your opinion, but you should agree that it's not only FNIRSI, as most of "the chinese comrades" cut costs/corners wherever they can. So for most of us, unless we are lucky and get a very old stock, the chances for flashing the OSHW and enjoying all its benefits are more limited as time passes. At least, when rolling the dice, my luck got me an apparently genuine 44pin MCU.

So, I rather invest some time on this unit than putting it aside or thowing it away. But to convert this schematic to the original one it's not feasible, as the changes are too many. Therefore if @madires and you and other readers can please support this new mod, I will appreciate it, and I think it will be of benefit for other "lucky" owners too.

My thoughts on finalizing this miracle of Chinese thought:
1. Remove STC and forget about it!
2. Try to improve the circuit

As I don't want to cut/lay many traces: I haven't spent much time trying to understand the m-firmware code, I don't know whether the communication between PD1<->PD2 is needed (which could be acheived by a resistor). And about pulling PD1 low for reset or menu access, and PD2 high for triggering the boost converter, I don't know whether this can be achieved by another STC substitution circuit, and/or by connecting it differently, and/or by some tweaks on the code. In fact, by reading the power supply part of the similar schematic (which I'm adapting from an m328p TC1 clone), on my unit the press of the button is detected by a low on pin 42, answered with a high on pin 16 to trigger the boosters. Could it be to use the traditional auxiliary PCB, but connecting P1 to Q2c and P3 to Q3b (by an additional resistor) the way to go, ar at least part of it? As I said, I don't know the code, so I can't tell.

3. Check the assignment of the display contacts to the microcontroller, as they may also differ from the standard ones.

I will. In the meantime, I can tell the ISP is the standard one, and gets recognized by my USBasp as an m324pa.

[madires]

Continuing with my WIP clone, I found a major issue with one of the latest m324pa transformerless TC1 clones, limiting the OSHW mod posibilities: the manufacturer modified the push button behaviour so is no longer directly connected to the STC, but between two(three) transistors, where the power_lock is no longer triggered by the STC but from the ATmega itself (pin16 high on my m324pa), and the push button sends a low on pin42 of my m324pa. Therefore, the known "two vanilla transistors mod" to flash OSHW firmware is no longer valid for this model.

I think you can simply ignore the STC of your TC1 variant, i.e. no need for the mod. Or remove it, as indman suggested.