1697 MCU Board - RT 100%

[Greendaycolt]

Hello all,

I was trying to replace the left joystick on a 1697 MCU board, and midway through the process, I noticed that RT was suddenly not working, it is now recognizing as 100% input all of the time. LT is working perfectly fine though.

Here are the measurements I have taken:

U10 pin 1 = 1.33V
Both U10 pin 2 and TP104  = .299V (0% trigger press) to ~17mV (100% trigger press)
U10 pin 3 = GND (had to jump to GND, previously was floating)

U9 pin 1 = 1.33V
U9 pin 2 = GND
U9 pin 3 = ~.667V (oscillates)
U9 pin 4 = 3.33V

I read RDC's notes in the 1537 thread that U9 pin 3 takes pulses from U1 - I am unable to verify the validity of this data but assuming it is working correctly since U11 (LT) is functioning perfectly.

Here is a picture of the board - it is beat up in the left joystick area from desolder heat and whatnot, perhaps a trace was severed or something.. I didn't do anything in the area of U10 besides jump U10 pin 3 to ground since it appeared to be floating when I tested it.





Any help is greatly appreciated!

[RDC]

That jumper shouldn't be doing anything, unless U10 was removed at some point and the pad for it was damaged.

Compare the voltage measurements between U10 and U11 and post the results.

[Greendaycolt]

Thanks RDC.

Measurements for U11:

U11 pin 1 = 1.33V
Both U11 pin 2 and TP105  = .290V (0% trigger press) to ~91.4mV (100% trigger press)
U11 pin 3 = GND

Measurements for U10:

U10 pin 1 = 1.33V
Both U10 pin 2 and TP104  = .299V (0% trigger press) to ~17mV (100% trigger press)
U10 pin 3 = GND (had to jump to GND, previously was floating)

[RDC]

Really need a scope to see what is actually going on with those lines, but the DMM measurements show it well enough. According to those, RT is technically working a bit better than LT. So the issue would have to be a BGA solder joint on the MCU for RT or the MCU has some issue internally.

[Greendaycolt]

Thanks RDC - you are right again!!!! As a last-resort option, I just took a heat gun and blasted the BGA for a few minutes. Of course, RT is now working perfectly. The right joystick potentiometers melted a bit so will go and try to replace that now too, lol.

Thanks again - you have always been so helpful and generous over the years on this forum!

[RDC]

Welcome.

[zis2104]

also having the same problem would you tell me how to measure the triggers?