$20 LCR ESR Transistor checker project

[alex_D]

Got this AY-AT kit and it works really well, mounted the ZIF socket in a standard 14 pin DIL socket so I can easily swap it out if need be, the 16Mhz upgrade
was easy-peasy, thanks to all involved with the open source firmware.

Thinking about getting another AY-AT kit, wondering what it would take to make it work with a 3 color e-paper display, i'm guessing it would help a
bit with battery life. https://uk.banggood.com/Waveshare-1_54-Inch-ink-Screen-Module-152x152-Electronic-Paper-SPI-Interface-Yellow-Black-and-White-Three-color-Display-p-1750623.html?imageAb=1&cur_warehouse=CN&rmmds=CategoryElectronicsPop&a=1676811431.4374&DCC=GB&currency=GBP&akmClientCountry=GB

[madires]

Recently we've tried an SSD1681 based EPD. It's so slow that it's infeasible. A b/w full display refresh takes several seconds, a three color update even longer. A b/w partial refresh is a bit faster (and blurry), but requires a full refresh after every few partial ones.

[py-bb]

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 have a Transistor Tester just like yours where the current limiting feature of U7 failed, but fortunately I avoided roasting D2. Therefore my unit is still generates 30V, but without any current limiting. I went ahead and installed the 2k2 series resistor between the junction of D2/C14 and the K test socket pin. This limits maximum short-circuit current to about 15mA.

IMHO putting in the 2k2 series resistor alone is good enough to prevent anything from smoking.

I continue to recommend replacing U7 too. The 2k2 series resistor protects U7. Even if a direct short is placed from K to A, the 2k2 series resistor keeps U7 safe and happy. After installing a new U7, testing with the 1k resistor should display a “zener voltage” of 5-6V. This indicates U7 is properly limiting the zener test current.

Replacing U7 is out of the question, the boards on mine are not very clean and I've barely used a heatgun before, but I can do the other one.

I think you have made a mistake though, the junction  between D2 and C14 is the K test point so you'd be putting it in parallel with a wire. Do you mean I should knife the trace? That doesn't seem reliable.

Thanks.

Ed in an earlier post you explain this'll require cutting the trace

I can't find that manual link and I'd like to see a picture of your modifications please - I noticed the replacements but not the cut trace in a post you made 3 pages back

[py-bb]

<offtopic>

...I have some diodes I need to test - should I be really careful in which way around they go?

What do you want to measure? Zener voltage? Forward voltage? There are simple ways to measure diodes (Google it). You don't need to risk your tester.
</offtopic>

This is a non-answer but it'd be nice to measure the breakdown voltage (or "the voltage" when using them as voltage regulators) - but mostly I just want a tool I can't break if some wires touch somewhere.

This is why I like hand-held (or differential) voltmeters, you can stick those probes anywhere and it'll be fine (except in weird contrived circumstances which if you bring up I'll point out that if I end up in those conditions something has already gone very wrong - like lack of job equipment & training a person in that situation would actually have)

[GraemeG]

I think you have made a mistake though, the junction  between D2 and C14 is the K test point so you'd be putting it in parallel with a wire. Do you mean I should knife the trace? That doesn't seem reliable.

Thanks.

Ed in an earlier post you explain this'll require cutting the trace

I can't find that manual link and I'd like to see a picture of your modifications please - I noticed the replacements but not the cut trace in a post you made 3 pages back

I don't have a photo to show you but you are correct in your first comment and in your edit. The track from the junction of D2/C14 and the K test point must be cut and the 2K2 resistor soldered in to bridge the cut in the track. This is definitely reliable and it fixes a flaw in this version of the tester.

Almost the first use of my tester was to measure the forward voltage drop of some schottky power diodes. I used the zener test terminals for a slightly higher current than the normal test terminals. In theory U7 is supposed to limit the test current but after just a few tests my unit failed and I discovered D2 totally burned. I don't know what current was flowing during the test but D2 was well past its specs! By inserting the 2K2 resistor the short circuit current is limited to a maximum of about 14mA into a short circuit on the K-A pins. ie. approximately 31V supply divided by 2200 ohms = 14.1mA

[Fuzzy Star]

<offtopic>

...I have some diodes I need to test - should I be really careful in which way around they go?

What do you want to measure? Zener voltage? Forward voltage? There are simple ways to measure diodes (Google it). You don't need to risk your tester.
</offtopic>

This is a non-answer but it'd be nice to measure the breakdown voltage (or "the voltage" when using them as voltage regulators)

As I said, Google it. Like Google 'measuring zener voltage' or 'testing zener diodes'

[mastershake]

so out of the insane amount of various clones out there can so done simply suggest one that works and will allow firmware upgrades if need be? I've been trying to get through this thread but with one eye down reading for me is a lot slower than it used to be. I'm about 1/4 way into the thread but think maybe I should have started on 330 and went backwards. I'm looking for really the best of the clones I guess but one I can upgrade or will that require changing the chip regardless. thank you in advance and I def appreciate any help or info. I'm heading back in for two weeks to the hospital for more cancer stuff and I'd love to get one ordered before going in. hopefully lots of boxes waiting for me when I get out.

[madires]

Which clone to get is a common question and you'll find the answer quite often on the last 10 pages. Be aware that some clones currently come with an alternative MCU not supported by the OSHW firmwares.

[mastershake]

Thats why I was asking does anyone have a recc seller or one you have recently bought that was legit? I just don't want to go through a bunch trying to get a good one. any AliExpress or Amazon etc link anyone could share if you know you got a legit one recently?

[indman]

mastershake,so this is the problem that no one will give you a 100% guarantee that the seller will send you the LEGIT device.Because in most cases, the seller has no idea about the contents of the goods.Today one person received a legitimate product, and tomorrow another person will receive an "illegal" product from the same seller.

[mastershake]

is there a certain board layout that one would want vs the rest of them at least? that sucks about not being able to get a legit one from any one seller.

[alex_D]

Right now from my experience, it seems the best option is to get the self build kit, that way you can be sure of getting a component tester you can easily self repair, mod and upgrade the firmware.

[elecdonia]

Right now from my experience, it seems the best option is to get the self build kit, that way you can be sure of getting a component tester you can easily self repair, mod and upgrade the firmware.

I recently purchased one of these kits. It is a "through-hole" PC board  using a DIP package ATmega328P mounted in a socket.

It had just one significant issue: The 680 ohm and 470k ohm "probe resistors" supplied with the kit were out of spec.

Specifically one 680 ohm resistor measured 691 ohms compared to the other two (675 and 676 ohms). The error is 1.6%
Unfortunately this prevented my tester from entering the "self-test" mode. It failed to detect that the probes had been shorted to start the self-test.

Re-reading this topic revealed these frequent instructions from the experts:

     "make sure your 680 ohm and 470k resistors are well-matched within 0.1%."

For a "quick fix" I put a 33k resistor in parallel with the out-of-spec 691 ohm resistor. The result is 677 ohms.
This immediately permitted "self-test" to operate.
My tester now works perfectly.

I do recommend these kits for people who are comfortable soldering "through-hole" PC boards.
There is no chance of getting a "fake" DIP package ATmega328P because nobody but Atmel/Microchip makes them.
Also having the MCU in a socket makes firmware upgrades and experimentation quick and easy.
And it is feasible to replace those crummy original resistors with ultra-high precision resistors.

[Messtechniker]

Moreover, if you kill the MCU with a charged capacitor,
you can in this case simply replace the MCU. 

[GraemeG]

Right now from my experience, it seems the best option is to get the self build kit, that way you can be sure of getting a component tester you can easily self repair, mod and upgrade the firmware.

Alex did your kit come with the clear plastic case or does this need to be ordered separately?

[alex_D]

My kit didn't come with case, I ordered it later. There are 2 types of plastic clear case, I got the angled one with space for the 9v battery underneath.
It's worth mounting the ZIF socket in a regular DIL socket since it raises a bit so you can operate the handle better.

I flipped around the 2 bottom terminals underneath so I could easily get at the protection diode if I ever need to swap it out.
I tested out all the resistors before I assembled the kit and found 4 were the wrong value and couldn't be used, not a big deal as I had the missing values
in my spares box.

I mounted the power connector for the battery underneath so making the wire routing easier. I also got a spare Atmega so I could program it on
a breadboard. The kit is worth it just for the PCB and the MCU alone.

[Pukker]

@ GraemeG.

Yes that case works fine.
I have made an modification to acces the SMD Pad
and easier to move the handle of the Zif-socket.
See post 2673

[GraemeG]

Thanks Alex and Pukker. I hadn't seen the angled case before and I like the idea of a built in 9V battery.

I also think I would modify the case as you did Pukker although I don't do much SMD work. Perhaps lifting the ZIF socket with a normal DIL socket is a simpler option although I would prefer soldered connections. Has anyone had problems with the ZIF or the MCU being mounted in sockets? The contact resistance should be low but I wonder if it could affect any of the measurements.

[madires]

I'd recommend to use precision sockets. Cheap ones tend to cause connection problems after a while, especially when the ZIF is a bit wiggly (no tight fit allows movement of the ZIF).

[davidut5]

Got new tester lcr-tc1, first measurement capacitor in zener diode kaa probes got some charge then moved to 1-2, tester got damaged.
Bought new mega328PB, 328p not available, read about pin 3 and 6, pin 6 not connected and pin 3 connected to ch340n pin 7.
5v ok when mega328 removed, but when in place after pushing start it gets very hot in short time and have to remove the battery to stop. No software on yet, but getting hot i think is not software related. Cut the circuit to pin 3 still getting hot. Resistance on 6v8 diode is 400k.
And about firmware, was looking for original, nothing fancy just need it to work. Managed to repair another lcr t4, replacing the mega328p, using avrdudes but for this did not find original firmware to download, just modified.
I am confused, board gives power only on pins 18(gnd) and 19(vcc), but datasheet say pins 3 and 4! I think the chip has wrong markings on it, probably on purpose. there is also no oscillator on board. What kind of chip this could be? Atmega3208 maybe?
In the picture not 100% but the one on the right is from tc1 and the left from t4.
Thank you.

[smg]

Delivered my T7 with a clone Mega328,
pcb similar to LCR-TC1(2) from the file TableClonesEN.pdf by indman@EEVblog
https://yadi.sk/d/yW8xa5NJgUo5z

[madires]

I am confused, board gives power only on pins 18(gnd) and 19(vcc), but datasheet say pins 3 and 4! I think the chip has wrong markings on it, probably on purpose. there is also no oscillator on board.

Most likely the MCU the clone came with is an APT32F172K8T6 with fake ATmega marking. Sadly we see more and more of those.

[davidut5]

Very disappointing, the mega328 was almost 1/4 the price of the tc1 tester and now not getting it to work any time soon!
I get it there is no firmware available for it yet, or the chip not available to buy!
Clone tester with a clone chip from a clone! 
Hope the mega328pb is still ok, to keep for the t4, just in case another charged cap comes around!

[Aldo22]

What kind of chip this could be? Atmega3208 maybe?

I have exactly the same circuit board and mine has a APT32F172K8T6 on it.
So I guess yours is a APT32F172K8T6 too.

[alex_D]

I'd recommend to use precision sockets. Cheap ones tend to cause connection problems after a while, especially when the ZIF is a bit wiggly (no tight fit allows movement of the ZIF).

This is what the Hiland M644 uses, pity you can't get a through-hole kit or PCB for this M644 layout  ;-)