[evlatests] when to replace EDFA chassis?

[Mark McKinnon]

The defective components in the EDFA chassis have been replaced,
and the chassis appear to be working fine (kudos to Jim J., Rob,
& Co. for a job well done). The question is when to replace them.

If current data quality is less than acceptable, then we should
replace them tomorrow (Thu, Jan 29).

However, if data quality is acceptable, we should replace the
chassis at a later date in a more organized fashion since a
lot of ancillary work is required (e.g. resetting levels and
delays). The VLA double maintenance days on Feb 10-11 are probably
a good time to do this. The two days should give us adequate
time to perform our work with minimal impact on observers.
Also, we would have time to recover if the replacement goes
awry and we need to re-configure the IF signal path to its
current state where the EDFAs are bypassed.

I haven't heard any recent complaints about data quality, so I
propose we adopt the latter strategy unless there are relevant
objections. Let me know ASAP (i.e. before tomorrow morning).

MM