[Johnson] Viking Challenger Questions

[rwayne at vnet.net]

I am trying to revive a Johnson Challenger. It has been a real challenge! 
My main problem now is with the crystal oscillator section. It acts "squirrley" and will not always operate on the same freq. as the crystal. 
I have a downloaded manual copy. 
I have the following questions for the members of this list. 

1. The schemetic show a 6DS6 for the oscillator tube. My rig came with a 6AU6 there. The wiring is correct for the 6AU6. Were there units that came originally from the factory with the 6AU6 or is the 6AU6 someones mod? Should I change the wiring to be correct for the 6DS6? I have the tube. 

2. My manual shows cap C11 in the plate circuit of the 6DQ6 driver. My manual says this cap value is 6.8 (I assume pf) and the mica in the circuit is stamped 1500 WVDC. Does anyone have a better manual copy and can verify the value of 6.8 pf is correct? This cap tests like it is open. 
BTW: I do not understand the function of C11 in the circuit. 

Any and all help will be appreciated. 
Thanks in advance. 
73 
Richard W4LN