Fender has used only a handful of different speaker types over the years.Here’s a list of brands along with their EIA codes.Besides being a popular and important amplifier in its own right, the Bassman also became the foundation on which Marshall and other companies built their high-gain tube amplifiers.5B6 Bassman amplifiers had two 6SC7 or 6SL7GT pre-amp tubes, two 5881 power tubes and a single 5U4G rectifier tube.This one has that high power twin tone like Keith's.
Initially intended to amplify bass guitars, the 5B6 Bassman was used by musicians for other instrument amplification, including the electric guitar, harmonica, and pedal steel guitars.
Wattage will again depend on what series and what amp head went with them, and are they Jensens, Oxfords, Eminence, or what brand? What color are they, what is the shape of the magnets, do they have aluminum dome dust shields in the center of the cones?
Still not sure what the speakers are, but I could assume that it has 8 ohm speakers that should handle 50 watts. I use a classic 30 (peavey) that I bought new 14 years ago. Well, Fender never made their own speakers, they were made for them by Jensen, Oxford, JBL, Eminence, and I think even CTS among others; and they put Fender's name on some of them.
Whether it’s a vintage amp or a recent model such as this Fender Pro Reverb, hum can have several causes.
Possible culprits include the preamp tubes, the power tubes, the hum balance resistors, and the power supply caps.