I worked on more troubleshooting of the whitening filters Tuesday afternoon

== Test Status ==

[done] Whitening gain switching test => Remaining issues ASDC overall behavior
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board

Issue 1: POP110Q did not show any gain switching [Resolved]

A DB37 breakout board was connected to the acromag front panel. I found that Ch6 (POP110Q) did not show any differential DC output. I searched around the other pins and found that the corresponding signal showed up on PIn36  instead of Pin35. Opening the front panel revealed that the internal wiring was wrong (Attachment 1). The wire which should have gone to Pin 35 was connected to Pin 36. By correcting the wiring, POP110Q started to show identical behavior to POP110I. (Attachment 2)

Issue 2: LSC reboot [Resolved]

A rough activity around the acromag chassis crashed c1lsc realtime processes (as usual). I ran usual rebooting script /opt/rtcds/caltech/c1/scripts/cds/rebootC1LSC.sh. This successfully restored the status of the vertex RT processes.

Issue 3: REFL33 different behavior between I and Q [Resolved]

REFL33I and Q consistently showed a difference (Attachment 3). The whitening board was pulled out and powered with an extension card. The raw outputs were checked with a function generator and an oscilloscope connected. The outputs for 33I and Q were identical (Attachment 4). So I concluded that the observed difference was an artifact of the checking script.

Issue 4: Whitening 3_8 did not switch at all [Resolved]

To switch the gain stages, each channel of the whitening board takes a DAC output from acromag and convert it into 4bit digital signals. For CH8 of the WF#3, this signal did not reach the instrumentation amplifier AD620. After tracing the signal on the electronics bench, it was found that the CH8 gain input to the DIN96 connector is not conducive to the input of the AD620. As there were no exposed pads between the DIN96 connector and the AD620 input (pin2), a wire was additionally soldered (forgot to take a photo). This solved the gain switching issue as the test result indicates (Attachment 5). The noisiness came from the whitening filter which can not be turned off right now. For this reason, the test of the whitening part is pending too.

The StripTool plot during the overall WF#3 test is shown in Attachment 6.

Issue 5: ASDC behavior [Unresolved]

First of all, at this test, I found that WF#4 was not responding to the gain change at all. This issue was restored by power cycling the acromag chassis (as usual).

The whitening filter #4 was pulled, and the behavior of CH5,6,7,8 (CH8=ASDC) was compared. It was found that the analog outputs were identical and the problem lies further downstream.

Issue 6: Illeagal REFL11 LO cable [Unresolved]

This is a newly found issue. The cable between the LO distributor and the REFL11 demodulator is not the legit solder soaked RG402 coax, but flexible coax (Attachment 7). This cable needs to be replaced in the end. But for today, it was not so that we can have a consistent configuratin as before.

Issue 7: Signature of a damaged POPDC cable [Resolved]

The cable for POPDC cale indicated some damage at the WF#4 side. It was not a complete damage, and therefore the solder coating was added (Attachment 8).