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Author Topic: 1708 with DR stuck pressed down  (Read 764 times)

Offline APintoZ

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1708 with DR stuck pressed down
« on: January 29, 2021, 03:03:01 AM »
Hello, I have a 1708 power/button board with a DR that is always pressed down. The board is is clean and there is no contact between the centre and outside rings of the button. The traces between DR, TP14 and pin 12 of the IC are all fine. Maybe this is a problem with D10? It looks fine, how would I go on to test it? I feel tempted to replace it with a working one from another board, but it's quite small and I don't have the right tools, I would prefer to exhaust other option before!

Thank you!
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Offline RDC

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Re: 1708 with DR stuck pressed down
« Reply #1 on: January 29, 2021, 06:07:05 AM »
I'd bet U4 is the culprit, but see how much Resistance is across D10. Check it both ways. Should measure open one direction, a Meg or more in the other. If it measures correctly, then U4 is probably bad. If it measures in the kilo or lower range, then remove D10 and test the controller. If DR is still stuck then U4 is the problem.
« Last Edit: January 29, 2021, 06:07:53 AM by RDC »
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Offline STIVIX

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Re: 1708 with DR stuck pressed down
« Reply #2 on: March 28, 2021, 09:35:49 AM »
 Would love to know if U4 ended up being the issue.  I have at the moment a similar problem.  DR and DU are both registering continually.  I've been trouble shooting TP14 and TP16 back to U4 and everything seem to be checking out. Do you know if the diagonal signal has its own TP?  Not sure if it works like that.  Either way any help would be much appreciated. 
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Offline RDC

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Re: 1708 with DR stuck pressed down
« Reply #3 on: March 28, 2021, 01:57:57 PM »
Diagonals don't have their own signal, they are just the combination of the two, DU/DL, DU/DR, DD/DL, DD/DR.

I've seen that U4 hang a button or two like that, so I'd say it's probably bad. Unless something was spilled on it and found it's way under the D-pad contacts sticker there.
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Offline STIVIX

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Re: 1708 with DR stuck pressed down
« Reply #4 on: March 28, 2021, 07:21:39 PM »
Thanks RDC!  I checked under the pads, they are clean.  Does anybody sell just that component (u4) or would you just buy a new  board? 
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Offline RDC

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Re: 1708 with DR stuck pressed down
« Reply #5 on: March 28, 2021, 11:29:01 PM »
If you can do SMT rework then you can get just that chip. Part number is in the 1708 thread here - https://acidmods.com/forum/index.php/topic,43981.0.html
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Offline STIVIX

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Re: 1708 with DR stuck pressed down
« Reply #6 on: March 29, 2021, 09:42:20 AM »
I've never attempted STM rework before.  I have read and watched a bit on it and understand it can be pretty difficult.  But I'll never learn if I don't try.  Wish me luck.  Thanks for being so helpful.  This site is amazing!
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