1992 blazer no power to radio constant

[351FUN]

Lost the radio, I have power to the switched/red wire but not to the constant/yellow one. The only fuse I can find is for the switched power. Where does the constant come from?

 

[351FUN]

The fused link to the courtesy lights is good. I have interior lights still.

 

[Donald Mitchell]

Does the yellow come directly from the fuse box, or something like the ciggerette lighter?

 

[351FUN]

As far as I know it comes from the radio pigtail and goes somewhere into the void. If it gets to the point that I have to physically trace that I'm just running a new wire.