[BILL]

I believe I've seen this red X on other GM radio IF cans , I think this could be something the factory put there , I do about 100 old Chevy + GMC radios for a vintage truck parts supplyer a year, I think a voltage check might be the way to find a shorted IF can as the voltage I've seen will sometimes jump from the primary to secondary, and not show up with a continuity check , The more I think about it I'd check that shield from the power supply to RF ,GOOD LUCK, BILL