$20 LCR ESR Transistor checker project

[madires]

Hi to all from Athens!
After reading a lot for this tester I decide to get one! 
So I bought this tester,4 days ago,plug in a 9V battery and worked fine....Suddently after a dozen of measures refuses to power on (only the green LCD light goes on when I press  test button)...I left it,check battery,connections,bad solderings etc,but all seems OK.,then I put it away....Next day worked well for some time, but after  4-5 measurements stops again....
What is going on

When powering on, does the display show the battery status briefly?

[Gyro]

Only a couple of things I can think of-

1. Beef up the supply decoupling after (and possibly before) the 5V regulator, add a 10uF if there isn't one already. Inductors and high value capacitors might put additional strain on the 5V rail regulation.

2. Check the pullup on the reset pin and associated track to the programming header footprint.

[firepower]

what's your battery voltage with backlight on ?

[nassosxlvbros]

When powering on, does the display show the battery status briefly?

When I push the test button (and tester works) yes,it shows first the battery voltage at 9-9,1 Volts...when trying to light up (no working mode hehehe...)only the green backlight of the display lights up and the upper line shows the 16 black (er,greyish) squares....

what's your battery voltage with backlight on ?

9 Volts are always there.... either with a battery or from regulated power supply.Working or not,voltage is rock steady at 9volts...

[opty]

... Another reason to avoid the slick but more expensive units with soldered in MCU. Socket versions are getting hard to find now but ordered with a few spare Mega328 chips can be a life saver.

I totally agree.

It's a pity there doesn't seem to be version that is both with socket and ISP header..

Opty

[paulie]

Bahhh.. It only takes 10 seconds to solder a row of single header pins to bottom of the board. Fortunately, except for reset, they all ISP pins are nicely grouped together there. My biggest complaint is putting the contrast adjust where it's impossible to access with display installed. A simple hole under the trimmer or using rt angle version would have avoided that.

[madires]

When I push the test button (and tester works) yes,it shows first the battery voltage at 9-9,1 Volts...when trying to light up (no working mode hehehe...)only the green backlight of the display lights up and the upper line shows the 16 black (er,greyish) squares....

Looks like a bad solder joint.

[firepower]

Black Squares on LCD is micro not working.  It not sending data  to LCD. Do you have 5V on regulator and micro ? You could check if crystal is oscillating, but they very reliable and most likely you have zapped your micro.

[nassosxlvbros]

I check everything lot of times,5volts are there (pins 7,20 ) when I press the button,stops when I release...Some times is working Ok some times not. Board is checked for everything wrong under the microscope,all solderings,joints,etc are perfect,all parts are OK,double and triple checked...

when it refuses to power on shows this pic:

[Shock]

I check everything lot of times,5volts are there (pins 7,20 ) when I press the button,stops when I release...Some times is working Ok some times not. Board is checked for everything wrong under the microscope,all solderings,joints,etc are perfect,all parts are OK,double and triple checked...

Were you always testing properly discharged capacitors? Make sure the button isn't bouncing perhaps capture it on the scope. Swap the battery.

Send it back if you can but if you can't, I'd resolder everything, then try soldering the test points directly to the component. In this case a resistor is probably the most simple test. Check the display connections as well. Then it's likely to be a faulty micro, design or software issue possibly caused by timing. But it's cheaper/faster to either get another one to rule out its inherent and then to perform a comparative test with duplicate components.

[nassosxlvbros]

Battery is fresh always,my power supply noise free also.Caps are discharged every single time....The only thing that remains is the microcontroller...faulty chip or something else... I already order another tester because is a much cheaper choice...

[MickM]

Hi;
  The very first thing that the software does on reset is set a pin to keep itself powered on.
If this does not happen then the CPU is not running.
Black bars on the LCD also mean the CPU is not talking to it.

So check for clock at the crystal pins ( I think it's around 1v distorted sine wave).
Look at the reset pin.
Look at power and ground pins, look for ripple.
If your CPU is socketed, unplug it, check the pins then plug it back in.
Look at the address and data lines - are they changing?

You may have a bad pcb, with a short.
Try freezing/heating it.
I had a cap meter that was under etched at the power socket.
Can you program a new chip ?
If smd chip can you change it?

I built a couple, then out of curiosity bought one.
They were all through-hole.

Mick M

[hapless]

I check everything lot of times,5volts are there (pins 7,20 ) when I press the button,stops when I release...Some times is working Ok some times not. Board is checked for everything wrong under the microscope,all solderings,joints,etc are perfect,all parts are OK,double and triple checked...

when it refuses to power on shows this pic:

In my experience, you can have solder joints that look absolutely perfect, but make intermittent contact. I would take out the chip and look carefully to make sure that pins are not bent. Next, I would examine the socket because sometimes flux gets inside the holes. After that, insert the chip carefully, making sure that every pin is inside a hole in the socket. This can sometimes be more challenging that it sounds. If all else fails, I would reflow or resolder, beginning with the microcontroller's socket. HTH.

By the way, your phone's camera doesn't seem to be able to take sharp pictures at such close distances.

[nassosxlvbros]

Thanks for the answers!
Sorry for bad the pics,but my mobile don;t like close pics...I'll try a trick on this.
Here some pics fron the pcb.
As you can see everything is clear.The 1nF cap between pins 20-21 is an extra option from me. R15 replaced,but nothing happens..

[nassosxlvbros]

And after all night stay today is working....I don't know for how long of course....

[firepower]

I reseat the micro chip its too far to the right in the pic. make sure its centered in the socket. If you can replace socket with a machined type even better.

I think thats a poor quality socket and is causing your intermittent failures. every thing else is soldered so should be ok. Having good photos does help us to know what your dealing with.
 

[FabioLucca]

Hello, I rode the circuit in the simplest way, used a Funduino (AVR 328p 16MHz) removed the LED connected to pin PB5 and changed the capacitor connected to the AREF 1nF, so far so sure, but he is indicating random capacitances including without probes of 100uF  or more 800uF order, besides giving error at the end of "ADJUSTMENT".
Interpreting SELFTEST or ADJUSTMENT data to find the problem?

I used the version "ComponentTester-1.17m" created by Markus Frejek/Karl-Heinz Kübbeler found in https://www.mikrocontroller.net/svnbrowser/transistortester/ course confurada agreement.
Resistors (680R and 470k) 1% tolerance
LM4040cim 2.5V 0,5% tolerance

OBS .: Text translated by google translator of Portuguese.

Thanks!

[madires]

Hello, I rode the circuit in the simplest way, used a Funduino (AVR 328p 16MHz) removed the LED connected to pin PB5 and changed the capacitor connected to the AREF 1nF, so far so sure, but he is indicating random capacitances including without probes of 100uF  or more 800uF order, besides giving error at the end of "ADJUSTMENT".
Interpreting SELFTEST or ADJUSTMENT data to find the problem?

Are you powering the tester with a SMPSU? Please try a battery or a linear regulated PSU.

I used the version "ComponentTester-1.17m" created by Markus Frejek/Karl-Heinz Kübbeler found in https://www.mikrocontroller.net/svnbrowser/transistortester/ course confurada agreement.
Resistors (680R and 470k) 1% tolerance
LM4040cim 2.5V 0,5% tolerance

k-firmware: Karl-Heinz
m-firmware: madires (also a Markus)

[FabioLucca]

Bingo! It worked, it worked perfectly!
Thanks madires!

[nassosxlvbros]

Yesterday tester makes the same....worked for a dozen times and then stops....As I don't have the necessaries to replace the chip and reproggram it, I must order another meter and waiting ........

[intrax]

thank you for a most enjoyable read. I just took mine apart to see what Atmega was onboard. The lying swine has sent me a 168 not a 328 as stated in this auction.

http://www.ebay.co.uk/itm/181718729730?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Time to send him an rude email I think. Not happy at this at all.

To Markus and Karl, very impressed with what you have done, as the saying goes Vorsprun… .. :urch Technik indeed.

What seller is your most gracious animal comment referring to? I am curious. .

[zomi]

Thanks tom.

Got it programmed and working ..

Just stuck on how to use makefile.
Wasn't able to sort the battery reading out.

And could someone update me, on the new firmware it has a batch mode enabled from the start.

[nassosxlvbros]

Update with good news! 
Today I receive a new meter kit from Banggood.For a $12.99 was a nice deal.The kit includes everything and a white box.So I asseble it and worked at once.After assembly, I check the "old" chip in the new pcb.It worked just fine.I measure a dozen of caps,about 50 resistors,some leds and 20 transistors.Every time meter powers up correctly.So I check again the old pcb.Measuring Vcc pins (1,7,20) and voila! a wrong smd cap at pin 1 was faulty!! The voltage on ths pin was 1,33V instead of 5 Volts.So I remove the bad cap and meter comes to life again!   

[pol35]

hello
this tester can do ESR in circuit ?


http://www.ebay.com.au/itm/311343672563

Is a good esr?
Some recommended seller ? link?

thanks
a greeting

[JacquesBBB]

hello
this tester can do ESR in circuit ?
http://www.ebay.com.au/itm/311343672563

Is a good esr?
Some recommended seller ? link?

Beware,  ESR in circuit can be troublesome.
https://www.eevblog.com/forum/beginners/how-to-blow-a-esr-meter/msg679338/#msg679338

I would recommend in this case to buy a version with the Atmega328  in DIP form on a socket.