Peavey Windsor to JCM800 Conversion.

[karpathion]

Note: V3 not V2. The mod circuit says from Pin 1 to C16. Removing C17 seems to take out V3b  from the signal path, unless it is meant to be jumpered. Then there's that extra stuff in the corner that connects to A,B,C and D. and disconnect P501
 I can't quite picture how all this works at the moment but valve 3b looks like it's working like 2b[preamp] with that weird high voltage input [ if jumpered at C17 ]

You are seeing the same thing I am. It has to jump across C17.