Recent tests have shown that CATHODE voltage breaks down at ~130V, continually leaking current and progressively dropping voltage, making febiad CATHODE testing impossible.
Thursday, January 23, 2025, 15:18 disconnected cathode wire from TBHT feed through, simply suspended in cage.
voltages are held for ~1min prior to increase. current will be reported after 1min and stable.
100V - 0.000mA
120V - 0.000mA
130V - 0.000mA
140V - 0.000mA
150V - 0.000mA
170V - 0.000mA
200V - 0.000mA
- the Cathode wire and power supply have no leak problem
Thursday, January 23, 2025, 15:42
Reattached the CATHODE line to TBHT feedthrough. Removed the 100||100kΩ resistor pair that connects TBHT to HVC.
Same process as before:
100V - 0.000mA
120V - 0.000mA
125V - 0.000mA
130V - 0.000mA
135V - 0.000mA
140V - current limit ---> dropped to 52V
-- The TBHT resistor pair is not the problem
venting chamber to investigate lines.
Thursday, January 23, 2025, 17:05
removed piece of broken ceramic that held the coil terminal
still current leaking, but it's not as immediate or as shorted. more resistive.
__V__mA__
30 0
35 2.4
40 6.1
45 12.2
50 19.5
55 32
60 gradually ramped up to limited
Thursday, January 23, 2025, 17:10
Disconnected COIL terminal. Behaviour still similarly bad. Doesn't seem to have improved.
Disconnected all TBHT and TGHT feedthroughs. ALL are now isolated from ground (AS BEFORE). TBHT + and - are isolated from all others, TGHT + and - are isolated from all others but 100R apart due to resistor at feedthroughs (as expected).
Increasing CATHODE voltage on TBHT+ feedthrough to test isolation.
V ____ mA
120 ___ 0
135 ____ 0
150 ____ 0
200 ____ 0
- The TBHT+ terminal does not leak directly to ground
Connecting CATHODE cable to TBHT(-) feedthrough to test
V___mA
130 __ 0
150 __ 0
200 __ 0
- the TBHT- terminal does not leak directly to ground.
Connecting CATHODE to TGHT+ feedthrough , and disconnected the 100R between - and +
V ___ mA
100 __ 0
150 __ 0
200 __ 0
- the TGHT + terminal does not leak directly to ground
Connecting CATHODE to TGHT- feedthrough:
V __ mA
125 __ 0
150 __ 0
200 __ 0
- the TGHT- terminal does not leak directly to ground.
connected cathode cable to TBHT+ cable.
V __ mA
30 __ 0
40 __ 0
50 __ 12
60 __ 35
70 -> 60__ 80 current limited
Disconnected 100R path between TBHT and TGHT power supply
CATHODE cable still on TBHT+ cable
V __ mA
150 __ 0
200 __ 0
TBHT is not the problem
reconnected 100 path from TBHT to TGHT. REMOVED varistors that connect TGHT to ground
V __ mA
100 __ 0
200 __ 0
These are likely the issue.
Reconnected varistors to confirm
SHORTED at 50 V -- 10mA, 65V gives 80mA, current limited.
Removed varistors. WIll have to acquire appropriately specced ones |