I started with step 2:
dissasembling and reconnecting the touch panel. No success.
When turning on the Pronto the white screen with blue letters PHILIPS appears but then, normally after a few seconds it should dim off and the boot process should start. That didn't happen. The white screen with blue letters remained.
I searched for firmware reload here in the forum. Accordingly I should turn on the Pronto while pressing Firm2, Firm3, Firm4 simultaneously, this will put the unit into 'complete firmware' mode. Where are Firm2, Firm3, Firm4  to press on my Pronto?
I launched Pronto Edit Prof. and I wanted to access the remote while the white screen was displayed. Pronto Edit told me: the Pronto is currently in settings mode. Please press exit on the Pronto and retry.
What does that mean? What can I do now?