Defective teletype oled display screen

hello guys,

i’d searched related topics in the forum but none of them is useful to my situation, also i’m new to this forum, please correct me if i post this thread in the wrong place thanks! my question as follows.

i was going to modified some components and design from og teletype by replacing dip style led and 5v regulator into 78l05(maximum 1.5a output), which could encourge more diyer to handmade monome teletype. also soldering processed by my diy oven so i consider my assembly process were fine, no solder joint or any failure, finally i could download the firmware to mcu successfully without error message.

one additional thing, i’m using at32uc3b0256 rather than at32uc3b0512 so the command to flash, erase and start will be different from the instructions at monome official website. memory capacity is a little close to its limitation(84%) but still far away from insufficient.

once above is done, i installed the oled display screen to pcba, somehow there’s nothing on it after powering teletype up, just a black screen. i’d measured supply voltage, all of them is stable at 3.3v/5v/-12v/12v without any voltage drop(if the current consumption is too high there should be a voltage drop and heat came out). i haven’t measured mosi, sck, clk with oscilloscope but there’s readable signal in multi-meter, so i guess the peripheral at mcu were still working.

any hints or suggestions for troubleshooting? so far i don’t know what would be the next step to debug.


1 Like

the basic checklist:

  • check the voltages at the OLED pin headers (use the schematic as a guide for what these should be)
  • if there are problems here, reheat the solder joints for both headers… you may want to do this anyway
  • confirm that the SPI signals are working (ie, the MCU is alive)
  • be sure you have the correct OLED part number?

I wonder if you can check if your teletype is working without the screen – “flying blind” so to speak. For example, you could power up, plug in a keyboard and type CV 1 V 1 and hit the ENTER key. Then get your multimeter and check the voltage on the first CV output (it should be near 1V).

  • yes, i measure the voltage from pint header ✓
  • no problem with solder joint i think ✓
  • yes, spi is working right now ✓
  • i bought the olde from digikey, pn is NHD-2.7-12864WDY3 ✓

there’s nothing changed after i type the command CV 1 V 1, would you give me other command to test with? so far i’ve tested with a cherry keyboard g80 1800, not sure it’s the correct model to test with. on the other hand i have a logitech wireless keyboard, but i don’t think wireless would work.

TR.PULSE A should cause the first trigger/gate output LED to flash.