CABCON (HDMI->RJ45 Converter Board) Notes

(Notes from tests done at PAB 10/12/21)

Settings (for all tests): Connected G (HDMI and CAT5): (J also plugged in with HDMI but unused basically)

Symptoms:

Does not read trim voltage when unbiased (values ~0 V)
When bias board to 49.5 V with GUI, adc reading is ~33 V and voltmeter reads ~0 V

When not biased and check voltage with CAT5 breakout board, we read values ~4 V (trim voltage?)
When bias to 49.5 V with GUI, adc reading is 49.3 V, measure with voltmeter and see ~51 V (all positive 51)

Were wrapped in packaging (unused)
When not biased and check voltage with CAT5 breakout board, we read values ~4 V (trim voltage?)
- BUT CAT5 channels are positive for 1+2, negative for 4+5, positive for 3+6, positive for 7+8
- When bias to 49.5 V with GUI, adc reading is 49.3 V, measure with voltmeter and see ~51 V (-51 V on 4+5)
When take data with monitor SiPM (connected on first channel, which for Stella tests was 1+2 on breakout board), we see a light pulse on channel 2 (corresponding to 4+5 on breakout board) (see schematics on next page)
Has worked with only 1 channel connected (monitor sipm) - this was the negative bias one!
Why does this work with negative bias??
- Tested this with just channel 3 as well, does bias properly (up to 49.5 V) and sees a light pulse
- Tried cable with all 4 channels connected: voltage doesn’t bias all the way (stops at 33 V)
Definitely can’t use channel 1 (our Stella channel 2) with the other ones bc it’s negative bias
Tried with just 2, 3 positive channels connected, still only see light on one channel…
Tried with the one negative bias channel and one positive bias channel, saw light on both…