Circuit Board Number Clarification

[DaveP]

The Mark IIC+ references only the RP-11a circuit board. I have an upgraded IIC+ that is equipped with the RP-10A board.
The serial number is 120xx so it is appears to be a IIC from birth.

Whats the difference between the two circuit board versions?

 

[Boogiebabies]

The RP-10A is based in the style of the IIB with LDR's for switching instead of the one relay. The RP-11A is the circuit board that was
redesigned for the IIC with a much different layout. It was also later the board used in the IIC+ with many component changes and
a different circuit layout. From what I could find out about the RP-10A, it was the early production IIC PCB. It was changed somewhere in the mid range
to the RP-11 in mid to late 1983. Hence, both boards have 1983 copyrights. The reason the RP-10 can be upgraded is the five LDR's. The rest of the
circuit Mike B. just does his magic on.

This info does not pertain to non-reverb models of the IIC or IIC+. The "R" in RP-10 or 11 is for reverb.
The SP-11A would be the pcb for these amps from IIC revision one and two.

 

[DaveP]

Thanks for the great detail. That explains the LDR switch item in the original work order.

 

[Boogiebabies]

Sorry, I had to check some notes on the SP-11A. It was used for the early IIC non-reverb and maybe even earlier.