930 PCB touch screen issue

[Beanscooker]

After searching internet for a long while finally got here with some hope.

I have 2 models - 730 and 930. Apparently 930 touch screen is not working. I swapped screen from 730 - the same thing. But surprisingly both screens working perfectly on 730 and touches are fully responsive – no issues.
So I assume there is a fault in 930 PCB.
Cutting long story short, I did soft reset, hard reset, wiped flash memory and internal 4gb memory, updated to the latest version software, than downgraded software etc - nothing helps.
Found some old post in another tomtom community forum that these kind of touch screen issues can be solved only replacing some kind of SMD circuit part.

Unfortunately I don’t know what part exactly is controlling touch screen.

That’s why I am here.

I am OK with soldering little parts but not very well in electronics to understand how it works.

Does anyone have an idea where I should look for the fault? Which part I should replace to get tomtom 930 working again? At least I could try
Many thanks for your help lads!
Looking forward

 

[canderson]

Position sensing of the resistive screen is managed by an A to D converter in the processor itself, and you really don't want to go there!
Very rare to see something like that happen. In my experience, those models are even pretty well ESD proof. Have zapped several in the winter when connected via USB will no ill results.

Can you tell us more about your specific symptoms with your touch screen? While less common on the 930, we've seen cases where grunge got built up between the bezel and the screen, causing either intermittent 'ghost' key presses or occasionally something more permanent. Now that you're handy with disassembly, try operating it with the bezel off to see if it changes the behavior (or behaviour, if you prefer!).

 

[Beanscooker]

Hi canderson. Thanks for the response. The screens I cleaned and tested already with bezels off. Didnt help. Both screens operative only with 730 model but not with 930. I am quite handy with disasembly little electronic gadgets and other small bits. I do sometimes car dashboards, steering wheels, radio units LED conversions and many other amateur/hoby stuff using solder iron or hot air. I have soldering station. Thought maybe there is a chance to fix 930 with my equipment. But if coverters are in the processor I am afraid to remove it from mainboard only proffesional equipment must be used like IRDA

 

[canderson]

Worse, I believe none of your maps would work with another processor (whose specifics are available only from another 930) -- which also contains some NVRAM that identifies the serial number ... to which your maps are keyed. Apart from an ugly SMT job, you'd be in that ditch as well, hence "you really don't want to go there". Wish I had better news.

 

[Beanscooker]

Thanks a lot for your help mate. You saved me few hours which probably I could spend looking for sollution if not registered here.