[Android Auto General] sTingA_:
Hello,

I got a Pumpkin Android Radio one year ago, it works fine.

A few weeks ago the touchscreen turned black, backlight is on, touchscreen works (touching the screen is recognized by the OS, music is playing,), but it shows nothing.

I know a bit where the "touch-buttons" used to be. I can rarely use the unit with touching in the right places to get music to play.

The only thing I did, was reposition the GPS mouse in my car maybe one week before the screen went black.

I only moved the mouse, I dont touched the radio at all.

I installed also an App to show the connected GPS-sattlelites the week before.

I don't know what happened.

I had no time to look up the failure, so I leave it 2 weeks with this error, and sometimes the display showed up again after 30min, sometimes after 5 min.

Really strange.

I am an electrician, so i thought that there must be two foil-ribbon cables for the display, one for touch, one for the display, the display cable must be loose.

I opend the unit but both connectors where in place and fixed with a drop of adhesive.

I looked a bit around.

On some point I found a soft switch button falling out the unit onto my desk.

At first it looks like an SMD coil, but it is a switch, like the ones from the front tactile buttons.

It looks like it breaks of the solder pads, but only on one side, the other side had no solder on it.

I checked all the boards but no switch button is missing.

I am not shure where the button came from, but it fall out of the unit, as i was looking around and shifting and tilting it.

My conclusion: They lost a switch in the factory and it fall into my unit. By car vibrations this stupid useless button shorted out some connection and now the display path is broken somehow.

So what i did so far, without fixing the problem and without breaking something, the unit is still working with the black screen and operation by blind touching works:

- checked the reverse input switching

- opend the unit

- checked the boards optically

- removed all foil ribbon cables

- DVD

- display "data"

- display touch

- main foil ribbon cable from the mainboard to the front daughter board

- small foil ribbon cable from the mainboard to the front daughter board

- ribbons from the daughter board to the two outer boards with the soft switch buttons

- I carefully disassembled the display unit, its a HannStar 721CT10255-A0 or WD010GHL40AE-D5

- resoldered some connections between on the "ribbon cable interconnection" between the original TFT and the "HannStar"-Connector

- I dismounted the daughter board an cleaned it with a board cleaner (some flux where left from the factory)

- I clean all ribbon cable connectors with a contact cleaner

- I dismounted the PX5 head board and cleaned all connections with contact cleaner

- I resoldered the doughter board with hot air and all ribbon cable connectors between the daughter board an the mainboard

- I resoldered the pins on the head unit with a small tip soldering iron

I looked up my flying around 7" Displays but they are not compatible.

I am not familiar with these units, but as i understand it:

The video signal from the head unit gets to the STM32F091 chip, gets muxed (rear camera, Aux, etc.).

after that it is send directly to the display.

On the daughter board there is a CHRONTEL 7026B-TF, but if i look up the pinout of this chip, its not connected to the display, as far as I can tell.

I am now at a point where it might be the extra useless button that killed something by shorting out some traces, the display itself is broken, the STM chip died on the display pins, or its not a hardware problem.

Is there anything I can test to determinate if its a hard- or a software problem?

Thanks for your help and I will appreciate your support.

( i have some pictures, but I am not allowed to post them)