Table of contents
- 1. 2011 July 13
- 1.1.1.1.1. 1) Check LBA RCU 8
- 2. 2011 July 1
- 2.1.1.1.1. 1) Check problematic RCU
- 2.1.1.1.2. 2) LBA tests
2011 July 13
A. Horneffer did:
1) Check LBA RCU 8
Measured the voltage at RCU 8 and RCU 16: both ca. 7.8 V
Impedance of the antenna cable 8 and 16: both ca. 90 kOhm (after letting it settle)
Connected antenna cable 8 to RCU 16, and cable 16 to RCU 8: No power on RCU 16, normal signal on RCU 8.
2) Swap questionable LBA cables with "good" RCUs
Some antennas stayed down: 8, 72, 78, 86, 148
Some antennas showed a good spectrum in a quick check: 68, 74, 130, 152
Some antennas showed varying power levels: 12, 44, 164, 178
Antenna 164 also showed a spectrum with increased (higher than normal) power at some freqeuncies: Oscillating?
3) RCU module 185 is broken
During re-connecting of all antennas the LBH connector of RCU 185 started turning! This connector is aparently broken. The RCU should be switched out. (I couldn't get a HBA modem mounted on a replacement RCU, so I put the RCU back so that the HBAs are all working.)
2011 July 1
K. Schlich and A. Horneffer did the following:
1) Check problematic RCU
As seen on June 30the tile 64/65 was not working properly, because RCU 64 did not provide the neccessary power.
We tested the impedance of the cables to tile 64/65 and 70/71: 64: 200 kOhm, 65: 21 kOhm, 70: 240 kOhm, 71: 24 kOhm
On removing RCU 65, the half-lit LED on RCU 64 went off. Measuring the output voltage on then gave the correct results, and the tile 64/65 worked. We also replaced the RCU 65 with a new board, for this we had to remove the current limiting NTC/varistor(?) on the new RCU module to place and connect the HBA modem.
All tests afterward (modemtest and spectrum check with rspctl) were successfull afterward.
RCU modules now in place:
64: -> 10638002067
65: -> 10638002051
RCUs to return:
broken with high ADC noise: 10638001026
were at some point at position 64 and did not provide power to the HBA tile: 10638002049, 10638002087, 10638002001
2) LBA tests
A quick check of the spectra of the LBAs gave the following results:
| RCU | Problem | RCU | Problem | RCU | Problem |
|---|---|---|---|---|---|
| 8 | low signal | 12 | low signal | 44 | low signal |
| 62 | Oscillating | 68 | low signal | 72 | low signal |
| 78 | low signal | 82 | deformed spectrum | 86 | low signal |
| 88 | Oscillating | 106 | deformed spectrum | 130 | low signal |
| 148 | low signal | 150 | low signal | 164 | low signal |
| 178 | low signal |
A visual inspection revealed, that the cable tie attaching one of the dipoles of antenna 106 to the ground was broken. Replacing the cable-tie fixed the deformed spectrum of antenna 106.
Dis- and reconnecting the cables and RCU boards of antennas 62 and 88 did not remove the oscillations. So we replaced the LBAs 62/63 and 88/89. New serial numbers:
62/63: -> LBA-24-818-00110
88/89: -> LBA-24-818-00031
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