AS_B is not used so no serious consequence but we started getting error about ASC-AS_B_RF45 whitening at about Oct/27/2018 10:00:00 UTC, that's 3AM local time on Saturday. The third 1:10 analog whitening for Q4 channel seems to be ON regardless of what BIO tells it to do, maybe a BIO cable/connector problem (again)? See attached.
Since I don't like to leave it totally broken I disabled the second whitening and enabled the third whitening and confirmed that all quadrants both I and Q made sense. But we need to remember that this BIO is not fully functional.
Is this the same one that Marc fixed a few weeks ago? If so, maybe there's a deeper problem that keeps coming back.
Same bat channel. Reopened the FRS 11582
I pulled the whitening chassis (S1100794) from ISC-R3 slot 13, and replaced the same chip as before (U13, which is an ALS573C octal d-latch). I also cleaned up some flux residue from both sides of the board and it works again.
During testing I noticed when the latch is active (low), and the adjacent pin is toggled low, the ground bounces enough to toggle the latch. This adjacent pin is the pin that has failed twice now. I measured greater than 2V overshoot both positive and negative which is beyond maximum specifications for this chip. This was only seen with the test rig, I tried but was unable to duplicate the results with the chassis installed.
This closes WP7906 for now...