Spellman Anode Power Module Failure

The Spellman Anode Power Module does not deliver high power 140Kv ?

It was working normally giving 140kv , then it did not give 140Kv, we reduce the power to 120kv, worked for some days then stopped, then 80kv .. then it totally stopped.

what is the failure and how could I repair it.

best regards

Yunes