The WFD problems seen on SM 1 could be related to the higher current draw
on the +5 V power supply. Since there are 11 WFD cards on SM 1 (& 6), the
current draws on the +5 V line are higher for these SMs. Also, the current
drawn is higher while the cards are digitizing (it is this value that will
be quoted henceforth).
At TAMU, we had measured the current draws for all the cards we tested.
For the 67 cards we tested, the current drawn on the +5 V line ranged from
7.02 - 8.82 A with an average value of 7.64 A. Note that the +5 V power
supply is rated at 90 A and with 11 cards the expected current draw is 84 A.
I obtained from Stefano Stalio the serial nos. of the WFD cards in each
SM and compared them with their current draws. Note that SM 1 has 7 out
of 11 cards with draws over 8 A.
SM 1 cards and their current draws:
----------------------------------
102 (1N01-07) : 8.10 A ***
111 (1T01-08) : 8.28 A ***
118 (1W08-14) : 8.46 A ***
140 (1B01-08) : 7.38 A
143 (1C09-16) : 8.64 A ***
150 (1B09-16) : 7.20 A
155 (1C01-08) : 8.46 A ***
159 (1T09-16) : 8.10 A ***
161 (1E08-14) : 7.74 A
169 (1W01-07) : 8.10 A ***
176 (1E01-07) : 7.38 A
The total current draw on the +5 V line is given below for the 6 SMs. There
are 5 cards (2 in SM 2, 2 in SM 5 & 1 in SM 6) which we did not test at TAMU
so I don't have the current draws on those. In this case the value listed
below has been scaled to the no. of cards in that SM. t Note that the current
draw on SM 1 at 88 A is very close to the supply rating (for SM 6 it is close
to the expected value).
Total Current Draw on +5 V line:
-------------------------------
SM1: 87.84 A
SM2: 76.325 A
SM3: 75.6 A
SM4: 74.88 A
SM5: 74.25 A
SM6: 84.348 A
A solution would be to swap the cards with higher draws on SM1 with spares
having lower draws. For instance, cards 143, 155, 118, 111, 102, 159
could be swapped with some of the spares listed below: 113, 121, 136, 146,
152, 154. This would reduce the current draw by almost 5 A.
List of Unused WFD cards & their current draws:
----------------------------------------------
113: 7.56 A
121: 7.20 A
136: 7.20 A
146: 7.92 A
152: 7.74 A
154: 7.7 A
137: 8.64 A
133: 7.56 A } presently at TAMU
134: 7.56 A }
157: 7.38 A }
103: }
105: }
108: } Not tested at TAMU, so current draws
117: } are unknown
127: }
129: }
130: }
164: }
- Ashutosh