Only humming or buzzing , no music or sound

There are parts in electronic music devices that change the electricity and filter it. The parts age an lose the ability to do that.

Does it still have a hum/buzz when NOTHING is plugged into the INPUT? If so, you MAY have a tub going bad. If the noise is only there when you have your guitar/effects, etc. plugged in, then the problem is the guitar grounding or effects faulty...
FIRST: When the amp is "cool", UNPLUG THE AMP POWER CORD FROM THE WALL! ! ! ! Then CAREFULLY remove and reseat the tubes one at a time. Be sure to insert back into the socket correctly. You MAY just have a bit of corrosion on the tube "pins"....

SECOND:Don't plug anything into the amp, turn on and warm up. GENTLY tap one tube at a time with a WOODEN pencil. DO NOT USE anything metallic (like a screwdriver....) and be VERY gentle. If the noise increases or decreases, you probably have a tube going bad...

That's all I have. If this doesn't cure the issue, best take it to a repair shop . . . .

You have a bad ground somewhere. Try different cables and check the effect channel port if it is tight and secured.

If it's disconnected from everything else, it may indeed be the power adapter. Try a different one, but also try it in a different location as well to see if it's picking up outside interference.

Check earth connection and check for static buildup around twist and slide controls by moving them briskly a few times. If humming stops or lessens for a while then gradually builds up again, it needs a service.

It doesn't happen often but I suspect that the high gain input jack is defective. With nothing plugged into either input jack part of the signal is grounded and there should not be any noise. It might be that plus a noisy preamp tube. Try swapping the first two tubes to see if there is less noise. Carefully bang your fist or use an insulated tool's handle to hear if the noise changes. It might be an intermittent solder connection as well.

The headphone connector is probably defective... loose connection...

First thing is to determine if sound is from the speaker or possibly the cabinet. If from the cabinet it is likely the power transformer is vibrating the chassis. This sometimes can be cured by adjusting the mounting bolts.
If the sound is from the speaker, then an electronic "cure" is needed. Please note that a very quiet hum is normal but if you can hear it 5 foot away, that is un-normal.

The hum would probably be due to failing component in the power supply. Unles you are adept at electronic repair, best to take it in for servicing.

If the hum is observable in headphones, then it is likely a power supply problem, usually a dried out electrolytic filter capacitor.

try placing your ear on the speakers, adjust the volume control up and down several times, you should hear a humming sound that goes up and down. if not problem with the stage before the amplifier, that is the sound processor. if you dont hear the hum. problem with the amplifier and speakers, including the sound ports or jack. dissassemble the unit. look for loose connections from speakers to amplifier.