While searching for a flash of IR in TMSX IR QPDs, TR_B looked like it has a very slow low pass filter (attached).

The difference between TR_A and TR_B in the digital world is that the dewhitening (40:0.4) for the fixed whitening is off for TR_A and on for TR_B.

So it seems as if these IR QPDs are without fixed (non-switchable) whitening, but we're supposed to have these.

Later Filiberto will go to EX, open the chassis and change the jumper to get the whitening back.