Go 740 Live touchscreen/PCB issue

[TheRascal]

Hi. This is my first post here and I hope I can get some help here. I've got Go 740 Live with not working touchscreen. I'm sure it's a problem on the circuit board. I've tried with working LCD and still was not responding to touch. Can anyone help me with some useful info which part of the board (apart from the LCD connector) is controlling the touchscreen? I've read a lot but couldn't find anything like this or solution for it.

Cheers

 

[dhn]

Google 'digitizer for TomTom 740' to see many links. Here is one:
http://www.amazon.com/Touch-screen-digitizer-TOMTOM-LIVE/dp/B00QAO3HLE

 

[TheRascal]

I don't need new digitiser. I wish it was that easy! The device is not working with working digitiser! That's what I'm saying. The problem is with the circuit board!

 

[canderson]

Google 'digitizer for TomTom 740' to see many links.

From what I read in the first post, he had access to a known good 740 LCD/digitizer assembly and that didn't behave any better. Could be the flex connector on the board, or could be the board, or could be the processor. Either way, repair is a total bugger. Digitization is done by two A>D converters on the processor itself. Reference voltage is applied to the digitizer, resistance of digitizer changes based upon location touched, resulting voltage is read and turned into location numbers by the processor.

 

[TheRascal]

Finally a proper answer. The device was dropped and that's how the digitiser got broken. I'll try to repair it tomorrow. I might kill it but it's useles anyway . Cheers

 

[canderson]

So was my assumption correct that you had a known good assembly to sub out long enough to see if things would improve, and they did not?
Now that we know it was due to a drop (finally, an almost proper scenario), that opens up several possible problems, but at least it isn't likely to be 'smoke' that's at the root of it. You'll want to pay special attention to the flex connector area of the board for any issues and in general around the board for any loose legs or lifted traces. The flex connector itself has to be managed carefully as well so as not to break the locking mechanism. Lifting an end tab just a little bit releases the cable. Are you certain that the cable is locked in tight on that connector? Does the tab on the end push down and STAY down after the cable is inserted? And I guess one obvious question -- is the display on the known good assembly 100% normal?

 

[TheRascal]

I'm positive it's issue with the board. I have 3 half working devices . Go 940 (restarts every minute but it doesn't restart in Flight mode), Go 540 (not charging but works normal when I fit charged battery) and this Go 740. All 3 LCDs are working. The ribbon connector is okay. When the clip is closed the ribbon doesn't move or sliding out. It must be broken leg on the processor. I'll start with re-soldering the processor without lifting it completely and same with the flex connector. I'll start different threads for the other 2 devices.