I pulled this from a magnatone amp and get no reading on it. From the magnatone schematics it seems like a 5148 or 4007 would do the job, but I am curious if I can find an exact replacement out there? Little help guys?
That is a selenium rectifier. A 1N4007 will replace it with no problems. Here's some info, which suggests that they are still being made, but selenium is toxic, and I think I'd just replace it with silicon. You might have to adjust a resistor somewhere to get the bias or bias range back to spec.