Author Topic: $20 LCR ESR Transistor checker project  (Read 3407624 times)

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Offline Sudya

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Re: $20 LCR ESR Transistor checker project
« Reply #8625 on: June 08, 2023, 07:56:43 am »
Markus Reschke firmware 1.49m.
LCR-TC2(T7-Plus V2.0) converted from LGT8F328 to Atmega328p, put a jumper where LGT8F328 programmer connection, 18 leg to plus, (21 can not touch, just an old photo).
I set the fuse, it does not turn off on capacitor test. Slightly amended the code, on my copy of the tester between 1-2, 1-3 and 2-3 shows very close values. It used to overestimate the capacitance and esr between 1-3.
EFUSE 0xF7 (Solution for switching off the tester when measuring capacitors).
Download LCR-TC2(T7-Plus V2.0 (Atmega328) firmware.
« Last Edit: June 08, 2023, 02:08:44 pm by Sudya »
 
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Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8626 on: June 09, 2023, 11:08:08 am »
Hi,

I have a GM328A that has been languishing in a drawer awaiting repair for about two years that I have only just had time to get round to this week.  It initially worked fine but began to fail now and again by displaying a white screen momentarily as the encoder was pressed to start it up.  Now that's all it does when the encoder is pressed.  I reflowed the solder on the TFT screen's pins as well as the socket into which it plugs on the main board, which made no difference.  I also flexed and tapped just about everywhere to see if I could get it to come to life again, but no joy.  However, during very warm weather (over 30°C) last year I thought I would try it and it worked, once, then died again.  Whether this was coincidence or the increased ambient room temperature I am not sure.  I have just taken it apart now and checked all the resistances of the resistors and they all measure according to their PCB stated values.  Looking at the soldering of the various components under a fairly high strength magnifying eyepiece I see nothing suspect.  I know this is not unquestionable proof that there are no dry joints, but I would like to avoid a full reflow of the board if I can.  I removed the ATMega328P to see what happens when the chip is removed, but the fault is the same.  Would this happen anyway as the chip is not installed, or is it a clue to the stage the fault must exist in?

So that I can understand the stage at which the fault is likely to be, is anyone able to briefly describe the procedure the GM328A follows as it powers up and engages the  ATMega328?

Thanks!

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« Last Edit: June 09, 2023, 11:29:48 am by UltimateX »
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8627 on: June 09, 2023, 11:18:38 am »
UltimateX,
First of all, you need to arm yourself with a circuit diagram for your clone and also with a multimeter, with which you should measure the +5V supply voltage when you press the Test button, which should be on the 7th pin of the processor. Next, make sure that the LED on the upper left side of the board lights up and stays on when you press the Test button.
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8628 on: June 09, 2023, 11:50:30 am »
Hi Indman,

Thank you for the schematic and advice.  I will test for the 5V shortly and feed back, but I know from previous testing that the LED does not light when the encoder is pressed.  I tested the LED yesterday with my DMM on the diode setting and it lights, so I know the LED itself is functioning normally.

Thanks!

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Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8629 on: June 09, 2023, 02:59:42 pm »
Hi,

Yes, I can confirm that +5V is reaching pin 7 of the µC when the encoder is depressed.

I then went looking for why the LED fails to light.  Looking at the schematic, the failure would imply that the base of Q1 (9014) was not being turned on.  I tested the base of T1 while depressing the encoder and I got 5V on the µC side of R8 (27k), but not on the Q1 side.  So, I retested R8 in circuit and it measures 27k. Hmm....  So do you think T1 is duff?

Thanks! 
« Last Edit: June 09, 2023, 03:02:23 pm by UltimateX »
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8630 on: June 09, 2023, 03:08:02 pm »
Check the functionality of C2 (it can be removed for a while) and transistor Q1.
Is the processor now inserted in the DIP panel?
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8631 on: June 09, 2023, 03:12:25 pm »
Yep, I didn't take the µC out.  It's been there during testing.

Let me remove C1 and see what happens.  I'll be back.

Thanks!
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8632 on: June 09, 2023, 03:30:00 pm »
I removed C1 and no change.  I took out T1 and tested it on my older M328 tester and it tests fine as an NPN transistor.  ???
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8633 on: June 09, 2023, 03:35:22 pm »
I wrote about the capacitor C2, which is installed in the base of transistor Q1. Do you have it marked as C1?
What is the voltage at the base of transistor Q1 now, if the Test button is pressed?
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8634 on: June 09, 2023, 03:51:01 pm »
Hi,  Sorry, I thought I read C1 on your original reply.  I need to remove C2 instead and test.

I measured the wrong 27k resistor - R15 instead of R8 - as they are beside each other and not sequentially marked.  I tested the voltage both sides of R8 and its 0V for both, so nothing is coming out of pin 12 (PD6) when the encoder is pressed.
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8635 on: June 09, 2023, 04:02:47 pm »
Removed C2 and no change.  Do you think it looks like I have a faulty ATMega328 or corrupt firmware?
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8636 on: June 09, 2023, 04:05:00 pm »
When repairing, you need to be especially careful, otherwise you risk losing the device forever.
Solder a jumper between the emitter-collector of Q1. The LED should be on when the encoder button is pressed.
What will be on the display in this case? The absence of voltage on pin 12 indicates that the software did not start normally.
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8637 on: June 09, 2023, 04:19:57 pm »
Thanks Indman.  The LED comes on anyway as power is direct to T1, not via the encoder.

What happens is the LED and screen both come on when the emitter and collector are shorted, but, again, a blank white screen.  When I press the encoder the LED goes off but the screen stays on with just the white screen.
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8638 on: June 09, 2023, 04:22:43 pm »
You need to check ATMega328 with a programmer.
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8639 on: June 09, 2023, 04:28:37 pm »
I have the one in the attached photo.  Are there instructions somewhere on how to check, test, dump the chip contents, etc?
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8640 on: June 09, 2023, 04:32:02 pm »
I have the one in the attached photo.  Are there instructions somewhere on how to check, test, dump the chip contents, etc?
In your photo, this is not a programmer, but an attachment to the USBASP programmer. Do you have USBASP?
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8641 on: June 09, 2023, 04:40:46 pm »
I don't have USBASP but I thought I could upload new firmware to ATMega chips with the USB attachment.  Can you suggest what I should I get to check and test my ATMega328?  Thanks.
 

Offline snapper

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Re: $20 LCR ESR Transistor checker project
« Reply #8642 on: June 09, 2023, 04:51:56 pm »
https://www.ebay.co.uk/itm/255552888808

the atm328 of the chinese clones are mostly read protected, so you can only load a new firmware!
« Last Edit: June 09, 2023, 05:05:40 pm by snapper »
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8643 on: June 09, 2023, 05:31:37 pm »
Thanks snapper.  So I buy the"USBasp ISP Programmer including cable" in your link and connect it to the chip writer device I showed in my photo previously, right?
 

Offline snapper

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Re: $20 LCR ESR Transistor checker project
« Reply #8644 on: June 09, 2023, 05:44:47 pm »
Yes is correct, but you still need software, I use this

https://extremeelectronics.co.in/avr-tutorials/gui-software-for-usbasp-based-usb-avr-programmers/

http://digitalwizard.co.in/download.php?file_name=extreme_burner_avr_v1.4.3_setup.exe

close VTarget jumper on the USBASP board and the usb connection to the board with the 28pin socket is then not needed.

https://www.fischl.de/usbasp/
« Last Edit: June 09, 2023, 06:17:02 pm by snapper »
 

Offline UltimateX

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Re: $20 LCR ESR Transistor checker project
« Reply #8645 on: June 09, 2023, 06:24:02 pm »
Thanks very much, snapper.  I will take a look.  :-+
 

Offline danielferran

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Re: $20 LCR ESR Transistor checker project
« Reply #8646 on: June 10, 2023, 10:31:28 pm »
hi, i am trying to put the firmware one new 328P, cause I burned the original one of the device, but there is an error on AVRDudess.... could anyone help me? i am a dumb in burning HEX files... sorry for my english to... i am using arduino isp..


Using the AVRDUDE Software it shows this error...on the att
  :-[
« Last Edit: June 11, 2023, 03:58:27 pm by danielferran »
 

Offline Fuzzy Star

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Re: $20 LCR ESR Transistor checker project
« Reply #8647 on: June 11, 2023, 08:52:37 pm »
hi, i am trying to put the firmware one new 328P, cause I burned the original one of the device, but there is an error on AVRDudess....

Using the AVRDUDE Software it shows this error...on the att
  :-[
Looks like your 'new' 328P is faulty. Where did you get it?
Are you sure your programmer is connected correctly?
 

Offline danielferran

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Re: $20 LCR ESR Transistor checker project
« Reply #8648 on: June 12, 2023, 02:32:10 pm »
I have checked the connections, the 338p IS New, from Aliexpress... I don't know, we have to burn a bootloader ir something like this on the New chip?
i have other 328p, but I don't know, os ter something measing?
« Last Edit: June 12, 2023, 02:35:25 pm by danielferran »
 

Online indman

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Re: $20 LCR ESR Transistor checker project
« Reply #8649 on: June 12, 2023, 02:35:28 pm »
danielferran AVRDude tells you that the ATMega328 is not detected. If you have other ATMega328 check them also by connecting to the programmer.
 


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