I picked one up, tweeter doesn't work, tweeter's fine, but the ceramic/sandstone a resistor broke loose at both ends. I know that it belongs somewhere on the actual jackplate part of the crossover assembly.. found it inside the cab.
I fixed one of these before, but can't remember where to solder it on. Last time it was obvious because the broken off wires were visable. It's the "jurrassic" version without an L pad, has a 3 way switch..can't find any pictures or schematics on line..
For starters, it would be helpful to know what "vintage" cab you have.
If it's a cab like a 1516 or a 1x15B that has the old 3-way toggle switch for the tweeter (High, Off, Low), then I would think the resistor is only for the 'Low' setting of the toggle.
it's exactly the version you mentioned, 3 way tweeter sensativity switch, just want to solder it back into place, but not sure of the actual solder points, thanks for your response
help with vintage mesa cab question 
version without an L pad, has a 3 way switch..can't find any pictures or schematics on line..
