Broken Quicko T12-952

The OLED screen of my Quicko T12-952 soldering station has been broken for some time now. It started with a single dead horizontal line (too bad I never got a picture of this). And after that the screen won’t turn on after restart, it would only turn on after a long pause between restart. So yesterday I finally decided to do something about it.

I opened the aluminium casing and looked inside. The mains-powered power supply seems to be OK, but the voltage output a bit too high: 25V unloaded when it should be 24V. In any case, after that I unplugged the power supply connector from the controller board and examined only the board.

Using a borrowed soldering iron, I soldered some wires to the controller board’s power input and powered it using my bench power supply. The soldering station powered up with the usual annoying loud beep, but the screen remains dead. After probing around with my multimeter, I still could not find anything wrong. The 5V linear regulator seems fine, the transistors seems fine, the diodes seems fine, the electrolytic capacitor seems fine, there’s no obvious scorch mark anywhere.

So I suspect it was the OLED screen itself that is problematic, because: the startup beep seems fine and the station can still power an iron just fine (tested before I begin the teardown). Next I desoldered the OLED screen from the controller board and tried testing it using my Arduino Uno clone. The OLED screen has pads marked SCL and SDA which are I²C pin names. So I figured that the OLED screen can be tested using a regular Arduino.

First I needed to figure out the I²C adress, so I used the i2c_scanner example sketch (from Arduino IDE > File menu > Examples > Examples for Arduino Uno > Wire > i2c_scanner). Using this sketch I got the address: 0x3C. Next to see if the OLED screen can display something. At first I used the ssd1306_128x64_i2c example sketch from the Adafruit SSD1306 library, where I changed the SCREEN_ADDRESS from 0x3D to 0x3C. This didn’t work: nothing was displayed on the OLED screen. So next I tried the ssd1306_128x32_i2c example sketch, without modification this time. This works: the Adafruit logo and then the usual animation is being displayed. But then it halted. So I pressed the reset button on the Uno, and this time nothing was being displayed. So I had just confirmed that the OLED screen/module itself is the problem.

Next: what if I used another OLED screen? I still have my 128x32 I²C monochrome generic OLED display from one of my previous post. So I soldered some more wires to the T12-952 controller board, and breadboarded it with the generic display. The result: it works. No need for firmware modification.

  • Just plug in the replacement OLED screen with the correct pin, and it works!
  • Without even need to rotate the screen, everything is displayed left-to-right the way someone would expected it. The display looks squished, but everything looks legible, if a bit too small.
  • The volt display on the OLED screen tracks the actual voltage from my bench power supply. As I increase the supply voltage, the volt display changes immediately.
  • The iron tip temperature control also works.
  • Now I am confident I can just order a generic I²C color OLED screen and be sure that it will work.

And yet, after all this, I still don’t know what causes the OLED screen to break in the first place.

See ya laters!