1. We have no new trays for tower 4!!
Annex 1 to NCR/FM/INFN/PI-468 Tower 4 bottom tray A.Brez, Pisa13/4/2005
We have no new trays for tower 4!!
Bottom tray s/n
NCR
description
disposition
011
467
Access to high side GTRC CSR register is intermittent at nominal DVDD voltage. Access to FE registers from this GTRC is not working with DVDD below 2.7V. Typical errors found are timeout and inconsistent read-backs
Not assemble on tower 4
009
469
Comunication with low GTRC is impossible at nominal DVDD voltage (2.65V)

2. Use of Bottom tray 002 (tower “0” bottom tray)
NCR100:C) In the case that need to use as flight an encapsulated tray, a vibration test ( as per LAT-TD par. 8.2) has to be perform on a tray(encapsulated) dismounted from Tower"0"
We are going to use the bottom tray 002 without the requested vibe test:
There are no more spare bottom trays, in every case we must use this tray and this is the only way to meet Tower 4 schedule.
Rationale:
There is no time now to do the test
The vibe test on a mid tray would be not fully predictive because it is done on a very different tray with very different mechanical properties.
There is an experience of 6 successful vibe tests of towers with 27 SSD layers per tower with encapsulated ladders without any channel loss (124,000 bonds). The bonds along the ladders are more robust, but are more solicited during vibe test (first tray mode is a drum mode)
The risk of a bonding failure is very little, much less than the risk of loss of channels on partially delaminated TMCMs that are currently in use
The bottom tray 002 has successfully passed the thermal cycle with the old higher values (+50oC,-30oC) and there is one only disconnected channel. It is the best bottom tray ever made.