I just got my new mm400 as I needed to go down from 8" to 7". I don't care about any dimming options I have to use the menu for. I want to dim it "in hardware", manually.
But here's the problem. Both displays (old 8" and new 7" mm400) use the same pwm-controller on their inverters, a texas instrumens tl5001.
I identified pin 6 to use for my desires... normally, it's got like 100k-200k ohms to ground. So I soldered a poti, which controls the brightness in a range of 40k to 80k ohms. At least, this solution now worked for some years perfectly.
So I tried to re-apply this solution to my new display, the mm400. Right after turning the poti, the screen goes dim just as expected. But after a few moments, the inverter switches off completely and I have to re-set power to get it back on.
How can I fix this "feature"?