scope capture from 2/12/2019

Conditions:

Test 1

100' twinax cable connected to port 1 of GGDII board 1.

Test load attached to simulated GG capacitance.

No external triggering

GG state: HV enabled, static open (G+ =-115v, G- = -115v)

There is a burst of three pulses that appear in regular intervals.

Burst:
Intervals: ~60 seconds apart
Burst rate: 30Hz (33ms).
Frequency: 1kHz

I see this burst pattern looking at board 7 and board 1. I did not look at other boards but I suspect this issue is present on other boards too.

Board 7: Port (channel) 28

Board 1: Port (channel) 1

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Test 2

Next I disabled the HV on all the GG boards:

No burst pattern is observed.

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Test 3
Next, I took one of the spare boards and powered it on the test bench with a bench PSU.

Conditions:

100' twinax cable connected to port 1 of GGDII board 1.

Test load attached to simulated GG capacitance.

No external triggering

GG state: HV enabled, static open (G+ =-115v, G- = -115v)

On the bench I do not see this burst pattern with the same conditions from Test 1.