Yellow Oled issue on Preenfm2. Went way too dark.

[mordaM]

I was unable to fix an issue on a Preenfm2 for a friend, so I’m asking here for help.
The Oled (yellow characters) remains at approx. 5% luminosity so it’s impossible to read anything. In the dark I can see something, nearly dark though (see picture), but it allows me to see that the unit works (and sounds) fine.
I asked the friend and he told me the Oled was working fine when he built the kit, but then at some point (months, years?) it stopped to work well and he didn’t play with it anymore.
it seems also that some pixels are missing (the G in „Engine“ looks incomplete).

I checked:
Version 2.08b
There’s no jumper JMP3.
The place for 68 resistor is left empty as it’s an Oled installed, not a LCD.
I tried with different resistor values for the Oled mod, from 1ohm to 50 ohm instead of 22 ohm but no difference (I’d say it seems even darker when the resistance is over 30 ohm). I also tried without a resistor, or with a resistor of 0 ohm, but then the Oled won’t lit at all.
I also reflowed every solder joints, all look ok.

Any idea what could cause the issue?
It seems that the issue is coming from the Oled/Oled board, but before ordering a new one and replacing it, I prefer to ask your opinion here.

[lokki]

I would guess it is a dead OLED screen as well.

[Xavier]

You can check the voltage on the top pin of the OLED resistor. Should be 5V with a 0 resistor.
Something like 4.5v with the 22 ohms.

But i also think it's a deadl OLED screen.

[mordaM]

You can check the voltage on the top pin of the OLED resistor. Should be 5V with a 0 resistor.
Something like 4.5v with the 22 ohms.

I see +4.9V (clean DC voltage) at the bottom pin of 22R and +4.0V at the top pin (a DC voltage mixed with a lot of noise).

[Xavier]

I see +4.9V (clean DC voltage) at the bottom pin of 22R and +4.0V at the top pin (a DC voltage mixed with a lot of noise).

Voltages are all good.
Even if it's difficult to understand what  (a DC voltage mixed with a lot of noise)" exactly means.

But if you try with a 0R resistor, you should get your 4.9v everywhere.
If the display is still dark with 0R , you can buy another one.