Odd issue here. Seen it several times after replacing the left analog sticks.
Issue:-
Left Trigger works on limit setting long and medium. When setting to hair trigger it doesn't register or sporadically activates when pressed.
I have ruled out the board interconnects (spring loaded finders) and ruled out the rear button board.
It would appear to be the hall sensor. is actually sensitive to heat since it is directly under the left analog module. I have replace the hall sensor from a donor board using the lowest temp I can. I get better results but still sporadic operation when on the hair trigger setting.
The blue rear button board has two leaf switched to determine the trigger sensitivity and here is what they do:
1: When the slider is on the longest setting the first switch is activated.
2: When in the middle setting medium through no switches are activated.
3: When on the shortest through (hair trigger / on off setting) the second switch is activated.
It would seem the hall sensor losses some sensitivity after being heated up so when the chassis is placed in the rear shell and being held down with finger pressure only the left trigger sometimes activates correctly. However...
When the screws or even some screws are tightened hard or even finger tight the trigger stops working.
I have ruled out the blue rear button board by using several known good ones and even soldered wires connecting them directly. Same issue.
I have removed the hall sensor (lowest heat possible) before removing the analog stick. Same issue.
I have raised the hall sensor up above the board by about 2mm and connected with wires so it's closer to the magnet better results but not perfect.
This has been driving me F*$King nuts and is taking it's toll doing these repairs. I'm about order some brand new hall sensors from Mouser, RS, Digikey (whoever can get them here fast) to confirm. This is the only thing I can think of.
Although these hall sensors are the exact same as in the other Xbox controllers they are never used as a hair trigger (digital switch) so the blue board must close different circuits with resisters to change the output of the hall sensor readings. So doing left stick replacements on Elite 1 controllers this never presented it's self because the trigger was 1: physically limited and 2: only medium throw, which had a wide tolerance.
Sorry for rambling. Anyone else seen this issue? Can we put more meat on the bone? I'll report back when I get the new hall sensors.