Billm replied over at TDPRI. He says that tube socket is fried, it looks like it was attempted to be repaired. I may have to get dirtier than I've ever done on an amp before.
BillM:
The tube board is obviously fried. You're looking at repairs there, not intentional mods. The easiest fix is to cut all of the traces except heater, separate the ribbon cables, and solder directly to the socket pins. Repair the traces to the heater as shown on my site. But you also have to keep the R3000 suppression diodes connected to pin 7 and ground.
If it were mine, I'd cut away the tube board and install chassis-mounted sockets. You'd need to relocate the small portion to the left that supplies the LED pilot light, carefully remove the R3000 diodes, and attach them directly to the sockets, between pin 7 and pin 3, which is also cathode/ground. The band faces pin 3, as you can see from a PJ schematic.
You need to extend the heater connections to the remaining piece of board that holds the 12AX7s. I do this all the time with Blues Juniors when I do the octal conversion mod.
The other mods are bias voltage and larger screen resistors. You'd want to measure the bias voltage at the tops of R21 or R22 to see if it's in the ballpark (-10.5 stock to -12.5 cool bias).
The input mod over on the right is probably unimportant. C2/R6 is just a little voicing circuit that bleeds off some highs. Fender has messed with these values, along with R5, over the years.
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