[Amps] Help With Command Technologies HF2500

[w3kl at w3kl.com]

I have a Command Technologies HF2500 with QSK circuit.
 
Earlier today when I fired it up on 160m, it behaved normally for a few minutes, but then I noticed that the grid current meter was pegging and the output (on CW) was zero.  No plate current but plate voltage is fine.
 
At first, I thought I might have blown the 3CX800A7s, but after removing the tubes and checking for shorts, I find none.
 
I suspect that the biasing circuit has failed.  Before I furthe tear down the system, does anyone have any insight into this probkem?  Perhaps some of you have seen this problem with an HF2500 in the past and can steer me in the right direction.
 
Thanks for reading - I appreciate any help anyone can provide.
 
73, Jeff
W3KL

Jeffrey K. Okamitsu, PhD, MBA
+1-609-638-5402