[Electronic M]

I believe ACE hardware sells 1/4" shaft couplers...if the new shaft sticks out close to 3/8" or more one should work...just saw the shaft off the old pot after measuring how far it sticks out and stick it in the other end of the shaft coupler (and make sure it sticks out the same length as the old one did). If ace doesn't have it Amazon or some online vendors will. You can get rigid and flexible shaft couplers...This application is probably better with the rigid kind. (Last spring ETF I turned down a nice doghouse because someone had deleted the focus knob and put on wrong knobs elsewhere and I thought it looked real bad like that).

I forget where the vertical output transformer is but if it's near the candohm chassis mount power resistors those are more likely to be the source of the smoke....I haven't had any fail for me, but of the 5 RA-103s I've had 3 of them had 40s-50s power resistors cobbled in to replace those resistors or sections of them. The one near the vert osc transformer (and the osc transformer itself) are common to find failed.