[Amps] Could Use Some Advice

[w4foa at comcast.net]

I have a sick Amp LK500-ZB and would welcome any advice and suggestions about how to get it back to life. 
The problem/symptom is when I turn the Amp on, within 1-2 seconds, the plate current shows approx. 300 ma, with no plate voltage applied. 
I suspected it might be a relay problem and ordered and installed a new relay...symptom exactly the same. 
Beyond that, I have not tried anything and that is my request for suggestions. 
Thanks for your help. 
73 
Tony W4FOA 
 PS: Last year I replaced the filter caps, Zener, plate choke and new 3-500ZG tubes.  All worked well up until now. 
  
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Watch your words; they become actions. 
Watch your actions; they become habits. 
Watch your habits; they become character. 
Watch  your character; it becomes your destiny. 
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