Sorry Daniel, I do not know the answer to your question, however, one can assume that the B version is a later version, and as such, may be better (or why make a B version). So, my inclination would be to check it out using the schematic in the manual and if necessary modify to make it a B version.?
Some of the MFJ equipment the only differences between versions are in cosmetics, some better performance due to tighter controls.
It is of course possible that the supply of proms dried up and they changed proms, so that would be the first place to look, you are going to have to compare the schematic and sort of reverse engineer your device.
What I have done in the past in a similar situation is to make a copy of the schematic, and as I trace the actual paths on the device, I use a highlighter on the schematic indicating that the trace or component is physically same. It is time consuming and somewhat arduous, but necessary to confirm they are the same.
Hope that helps
--
Jeff - NZ2S
HB9DDS
JeffBanke
