Chosen Solution
I have disconnected the LCD without disconnection it from the battery….stupid. But OK now I have the common problem of not having a backlight. I have had this problem before a year ago but then it came up “by it self” after a while. What id did so far without result:
- power off/on
- reset settings
- hard reset
- disconnect from battery for a night
- checked connection of ribbon cable
- Replace the filter and the coil. Before replacing the filter and coil I already had a voltage level of approx. 3.8V at the backlight pins / outlet of filter. So my guess was replacement of filter / coil should not be required. But I did anyhow but without result. Still after replacing I have a voltage level of 3.8 after filter, diode, coil and before the coil. I did not replace the diode as it is blokking in one direction and “open” in the other. So there is no 18V available… So what else can I do, besides using the Ipad as an advanced cutting board? I
The backlight IC (PMIC) is probably damaged. It’s purpose is to drive a modulated square wave (PWM) to adjust the boost the voltage. It is in effect, a boost converter. So if the voltage is not boosting and you’ve already changed the coil, the diode appears good and the filter is fine, then change the IC.
