$20 LCR ESR Transistor checker project

[Yuriy_K]

Measurement examples did not fit due to limitations.

P.S. Made a new body. Once placed in the housing, it must be recalibrated due to the effect of the dielectric between the three lower redundant inputs.

[snapper]

hi yuriy,
don't understand the green connection and the series resistor for BL certainly ohm and not kohm!?
do you also have the firmware as hex and eep and would you kindly provide them?
I am currently working on an (improved) pcb copy and will take the changes into this immediately.
I also found this booster mod (for the zener test voltage) on github

[Yuriy_K]

don't understand the green connection and the series resistor for BL certainly ohm and not kohm!?

In my board there was 2-3 ohms between AGND and GND - a defect in the board. Eliminated with a short jumper.
New displays require resistors of the indicated kOhm ratings.
I just finished fixing the firmware yesterday, but I haven't fully checked it yet. Here are the fixes for today.

[snapper]

New displays require resistors of the indicated kOhm ratings

yes, the 5x 10k in the data lines are fine, but 68-100k in the line for the backlight?
there won't be much light! 30\$\Omega\$ are right ! display needs 3,2V 60mA for backlight.

[Yuriy_K]

there won't be much light! 68-100\$\Omega\$ are right ! display needs 3,2V 20mA for backlight.

I indicated the real value in my circuit, if you want to burn the display, put whatever you see fit.

[snapper]

hello,
on the board a 1k resistor R6 is already inserted in the base line of the transistor,
according to the data sheet pin LED can be connected directly to 3V3 for maximum backlight,
nothing will burn there! where can you get the information for the 68-100K resistor ?
regards

[indman]

snapper,
There is a factory datasheet for each type of display, which indicates how to connect the power and backlight circuits.
This datasheet and be guided by the connection. This is a childish question for a person who understands electronics.
It's just that displays of the same diagonal exist have slightly different backlight control - in one it is controlled directly through a limiting resistor, in the other by a certain voltage level to the base of the control transistor or PWM.

[snapper]

hey,
this is a project by Boleslaw J. and my idea to develop a circuit board for it.
the project has now been tested and completed and the pcbs are available.
see https://www.mikrocontroller.net/topic/transistortester-avr?page=31#7381379
and ongoing.
if interested on adapter PCB please send me PM

[madires]

The ATmega644 adapter for the AY-AT clone is accompanied by a modified m-firmware with added graphical output of the IR signal in the IR receiver/decoder function. That mod is done by Boleslaw J. (boleslaw_43): https://github.com/madires/Transistortester-Warehouse/tree/master/Firmware/m-firmware

Edit:
And the PCB layout of Boleslaw's ATmega644 adapter for the AY-AT clone (format: Sprint Layout 6): https://github.com/madires/Transistortester-Warehouse/tree/master/Hardware

[.RC.]

Is the 644 Upgrade to the AY/AT board via the daughter board only for the increased memory. I ask as I cannot see where you can easily use the extra pins available on the 644. I know all the pins on the 328 are used, so I thought you were restricted to what you can switch on in the firmware.

[snapper]

The control of the display has been changed to hardware SPI and there is a new generator output GEN (OC1B on pin 13) on the daughter board with a frequency output of 2 MHz.
the rest e.g. modified m-firmware with added graphical output of the IR signal, read in mikrocontroller forum posts
https://www.mikrocontroller.net/topic/transistortester-avr?page=31#7401381
search for the contributions of boleslaw j. (all in english)
the new GEN connection of the adapter can be wired to the terminal block of the old one, as this is no longer required,
the old connection / conductor track must be severed for this purpose!

[Sudya]

Comparison of LCR-TC2 testers and their firmware.
EFUSE 0xF7 (Solution for switching off the tester when measuring capacitors).

[Sudya]

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.

[UltimateX]

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!

Ad

[indman]

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.

[UltimateX]

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!

Ad

[UltimateX]

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! 

[indman]

Check the functionality of C2 (it can be removed for a while) and transistor Q1.
Is the processor now inserted in the DIP panel?

[UltimateX]

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!

[UltimateX]

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. 

[indman]

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?

[UltimateX]

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.

[UltimateX]

Removed C2 and no change.  Do you think it looks like I have a faulty ATMega328 or corrupt firmware?

[indman]

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.

[UltimateX]

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.