$20 LCR ESR Transistor checker project

[stj]

ST7565

there is no ST7585

[roli_bark]

ST7565

there is no ST7585

Yes, there is. It's a 66x102 matrix LCD
https://www.crystalfontz.com/controllers/Sitronix/ST7585/306

[mauroh]

Is it just a typo in my message, I will correct it. The ST7565 is the correct display for the BGDIY M12864.

My list is correct, but it actually refer to the 1.22m version.
For the 1.23m 1.24m you need to modify also the config_328.h where the LCD section is located now

Mauro

[roli_bark]

FYI - for the 'banggood' version, the LCD display part # is JLX12864G-378

For whoever wants the datasheet - the manufacture (JLX) site:
http://jlxlcd.cn/china/productshow.asp?nClass=97&PClass=0&ID=280
(bottom of page)

JLX12864G-378-PC (with Chinese character library)
JLX12864G-378-PN (without Chinese character library)

HW Timing & Code examples included.

[Harm2k16]

stj, thank you again!
I'll go on experimenting with this.
TY

[flywheelz]

Please, I need help.

I have put together this kit from http://www.aliexpress.com/item/2016-DIY-kits-TFT-LCD-M328-Transistor-Tester-LCR-Diode-Capacitance-ESR-voltage-meter-PWM-Square/32649811953.html?spm=2114.13010608.0.93.OBbTox  I had to solder the three protection smd parts myself.  Kit does not include test capacitor.

With 9v batt plugged in DC jack and encoder pressed down, there is 235mA draw from batt.  The T3 labeled 9012 gets hot  .  0 volts on socket pin 7.  In circuit the 9012 and two 9014 transistors test good.  The 5v reg 7550A-1 shows shows some voltage drops on every pin in both ways.

I have dis-soldered the LED and surge suppressor but no help.

Any ideas?

Update:

Thanks to stj for pointing it out, I soldered the SRV05-05 front to back.  Once removed device worked!

[tom666]

@flywheelz:
This is probably caused by a short circuit at the output of the 7550. This may be a short circuit on the PCB, defective capacitor or damaged the 5V stabilizer.

[flywheelz]

I've pulled the 7550 and connected in directly to 9v bat and it puts out 5.05 volts.  Also, without 7550 the 9012 is runs cool and switches on providing 9v to VIN for 7550.

Where is 5V stabilizer?  I don't have schematic from seller but looking at ttester.pdf page 10.

Thank you!

[stj]

did you test it with no atmel or display?

btw, i see you damaged the atmel socket! - i would have used a turned-pin type.

[flywheelz]

did you test it with no atmel or display?

btw, i see you damaged the atmel socket! - i would have used a turned-pin type.

No atmel or display testing for 5v on pin 7 first.

Yes one pin 22 was violated by dvm probe, I will bend it back with a needle    But the LED wasn't so lucky, ended up with one leg 

[stj]

first, check the resistance between ground and the input and output pins of the regulator - to see which side the mystery load is on.

[stj]

and make sure the 6pin diode-pack is on the right way!

[flywheelz]

first, check the resistance between ground and the input and output pins of the regulator - to see which side the mystery load is on.

With 7550 removed - GND to Vout 20k ohms; GND to Vin 13.29k ohms.

and make sure the 6pin diode-pack is on the right way!

I can't make out any writings on 6 pin turd.  On the pcb I saw a white dot, I took it as pin 1 and on one side of the brick there is a small tab sticking out, I took it as pin 1. 

Is it on backwards?

[flywheelz]

@stj, I think you nailed it.  I can barely make out scratched "| VO5" with one eye and tongue at a right angle and that would mean I put it front to back.  I will have more time Fri evening and will try to remove the diodes pack and put 5v reg back.

[stj]

all the kits i have seen, the SMD stuff was already fitted.
was yours different?

[tom666]

Where is 5V stabilizer?  I don't have schematic from seller but looking at ttester.pdf page 10.

Schematic from seller:

[flywheelz]

@stj, yes,  my kit came with smd parts unpopulated.  Link to seller and picture of what I got few posts back.

@tom, thank you. It matches except for my kit has no input reverse protection diode.

[flywheelz]

Does it matter which way I place the suppressor AK1521 diode? I remember flipping a coin when putting it on due to lack of markings.

[vinceroger]

Does it matter which way I place the suppressor AK1521 diode? I remember flipping a coin when putting it on due to lack of markings.

in stj post 6 post up theres a good picture you can zoom in on it looks like the part may have a white line/band on that goes towards the top of the tester

[flywheelz]

We've made some progress!

The short was caused by the 6-pin diodes chip I've soldered incorrectly.  Once I removed it the tester is showing some life.  Thank you stj for pointing that out.

If I press in encoder for a second, the screen flashes white.

If I press and hold encoder, I see in green text:

• Selection:
• Switch Off
• >Transistor
• Frequency

Then it goes to:

• Bat. 8.7V OK
  
• VCC=5.04V

Then:

• Bat. 8.7V OK
  
• Vext=0mV

When I let go, unit turns off.

What now???   Its like something atmel not latching something to run.

Do the MC5 6-pin chip and AK1521 suppressor required to run?

I made sure pin 22 I damage is ok.  But looking the board, pin 22 is not connected to GND as schematic shows.

Update:
Other thing its missing is the LED and that looks like its required for the current path for s9014.  Is it correct?

[stj]

look at the schematic, there is a transistor or 2 that hold the power on.

and you DO need the led - it's not just for lighting up.
no led will cause this.

[flywheelz]

I don't have any LEDs at the moment.  So I've soldered in a 3.3v zener the normal way instead of LED and now the unit stays on    I think the original led had was1.8v forward voltage drop.  Do I need exact LED as original?

[GBowes]

@stj: Good call on that TVS diode orientation.

@flywheelz: The LED is not critical. You could even leave the zener in but as the Vf is only about 0.65V, your current through that path will be higher (about 3-5 mA). I would suggest putting in any 3mm or 5mm red, wht, green LED. It is nice to have an indication that the device is on although it should power off after a timeout and you can also see the display.

Graham

[flywheelz]

@stj: Good call on that TVS diode orientation.

@flywheelz: The LED is not critical. You could even leave the zener in but as the Vf is only about 0.65V, your current through that path will be higher (about 3-5 mA). I would suggest putting in any 3mm or 5mm red, wht, green LED. It is nice to have an indication that the device is on although it should power off after a timeout and you can also see the display.

Graham

I think the zener might be causing a problem.  The button is not registering after power-up.  I can't enter calib.

[stj]

dont you have anything in the junk pile with an led?
smd would be nice - it wouldnt be sticking up so much.
i do like smd led's