Summary:
When we tested the in-vac picomotors on HAM3 again though these picomotors and also in-vac QPDs were tested OK before (here's the alog of these tests done by me, Cheryl and Daniel), nothing moved. Without these things, HIFO test never works.
The problem was traced back to an error in in-vac cabling. ISC IR QPDs were connected to the picomotor feedthrough and vice versa though I have no idea why this happened (see the comments attached to this entry for details).
The cabling was fixed and the picomotors now work again, but ISC QPDs are likely broken because of multiple attempts to drive picomotors back and forth, which put more than 100V on diodes. We used laser pointer to test the QPDs with the handheld QPD interface but were never able to convince ourselves that they're working. We forgot to test if any of the quadrants are short-circuited.
IO QPD for MC transmission should be OK as it is on a separate cable.
Anyway, we have spare QPDs and we'll replace them on Monday, entering HAM3 from the north opening. It's probably less than 2 hours for replacing, plus an hour for testing. We've done the same thing in EY and we know how to do this.
Spare S/N 20 and 24 from our stock of IR QPDs were bagged and left in a clean room by HAM2 so we can continue on Monday morning.
Picomotors and ISC QPDs both have two in-vac cable sections. The first section is routed to cable bracket 3 (CB3), then the second section goes from CB3 to the vacuum feedthrough, and apparently the second sections were crossed and mixed up.
Before we fixed the error:
After the problem was fixed (everything is consistent with D1101463 and D1002874):
Other things to note:
1. What happened?
It's really baffling as everything worked last September as I noted above.
Either things were mixed up from the start and somehow I managed to connect the test equipments (the picomotor driver and the QPD tester) to feedthroughs in a consistently wrong manner so everything worked, or things were OK back then but mixed up later for whatever reason.
Thing is, I remember having looked at D1002874 (Flange Layout H1 HAM3) and D1101463 (Cable routing configuration HAM 3) multiple times, especially former, before connecting the picomotor driver on the feedthrough exactly because I was worried to break QPDs (after all, this is not the first time we broke QPD, see this alog). It's extremely unlikely that what I did at that time was inconsistent with D1002874.
2. Picomotor driver unit 3 is funny.
During the testing, we disconnected the in-air cable from the picomotor controller for HAM1/3 (unit 3) and connected a picomotor directly to the front panel. It drove the picomotor, but it was VERY quiet and slow even though we selected the fastest pulse rate (500Hz) from the MEDM screen. No screeching at all.
We did the same test for the driver unit 4 that is used for ICST1/IOT2 and it was acting properly.
We never bothered to swap the Beckhoff cables of these units to see if it's a software problem or the drivers.
Anyway, if it turns out to be the driver, we'll swap it with the test unit that is sitting on the cart in the LVEA.
Here is a picture of the actual cable bracket. This was taken after we had fixed the cabling.