Fender stage 100 loud hum/buzz. Even with the guitar plugged in. And also when it’s not

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.

On mine, the guitar input jacks get tarnished and causes all kind of interference and noise. Take a Q-Tip soaked with WD-40, run in down into the jack and brush up and down. Don't overlook the filter caps as they are a common cause of noise. You need a capacitor checker (the older tube type) to thourghly check those out.

"Noise" is not a very good deescription... is it hum? is it static like? is it a buzz? Hum pickup by the pickups of guitars are common and some pickups are worse. If it is hum move the guitar away from magnetic sources like amps, motors, flourescent lights, dimmers... etc. Sme guitars have grounding problems and touching them varies hum. Also, do NOT let the guitar "hear" the amp as it can feedback at frequencies above your hearing even. Do some "sniffing" by moving the guitar and the orientation around the area seeing if you can find hot spots of noise to avoid.

i) Disconnect one lead of loudspeaker & insert an open-ended guitar cable into headphone socket.

ii) Put a dc voltmeter across open end jack then turn Frontman ON for a few seconds.

iii) The reading should be about 0volts - if the voltage is high (27v), then it is likely that the PA chip TDA1514A has blown.

iv) If,however, the voltage is correct in iii) , then reconnect speaker & put guitar cable into the POWER AMP IN socket & connect other end to guitar...Turn on briefly, if there is still hum then fault is in the output stages & will require chassis removal to solve.

Here is the schematic:

http://elektrotanya.com/fender_vibrolux_6g11_schem.pdf/download.html

Check the quality of the DC bias as being free of ripple.across teh 25 mfd/50v cap filtering the bias.
If much ripple there, replace the cap. Also the .05 bypass on the swinger of the intensity control.

This should be an easy fix, but you might need an oscilloscope to diagnose it quickly... or just parallel caps across these to see if it kills the hum.

The main high voltage filter caps are also suspect as well as the bypass of power to the ealier inverter stage a 16mfd/450v

There are lethal voltages in this so use great caution when troubleshooting... the caps hold a nasty charge.

Is it the amp for sure? You need to try these things first :

Plug your guitar and lead into another amp. Does it buzz?
If so, Change the guitar lead with a NEW ONE.
Still Buzzing? Your guitar needs attention.

Ok so if it's not noisy in another amp, turn on your fender with nothing plugged in. It should be silent? Is it? If not, check to make sure no ones messed with the earth lift switch.
Next, you should try it off a different ring main. If you have upstairs sockets and downstairs sockets, they should be (but not always) on a different ring main. Try it? If you live in a flat for example, or are unsure, try it round a mates house. If it's noisy off one ring and not on the other, you have some mains interference from something else plugged into the ring main and it's not your Amp.

Is it still noisy?

Well so far, I'm hoping you have been using it all Clean and direct with NO FX Pedals and such like. These thigs can add numerous buzzes and hums to any rig. Again break it down, try each one by one until you get the rid of the buzz.

If after all this, your Fender is still being noisy, you can safely take it to your nearest music store to get it repaired without feeling like a plonker :-)

If you unplug the guitar cable and STILL get the hum, the unit has a defect... return under warranty.

If the hum goes away when you unplug the cable, replace the cable and see if new cable fixes the problem. If it does, the cable has a bad shield.

If the cable didn't cure it, then the guitar has a defect. Remember that some guitar pickups are sensitive to the magnetic fields from the amps... only cure is to either use humbucker types or be a distance away from the amp.

easy kiss my ****

If you are saying that you are plugging a guitar cord into an input on an amp without the guitar on the other end and you are getting a hum or buzz with the volume turned up ; that is normal. If you are getting the same results with a guitar plugged in it means the ground wire to your output jack on your guitar is broken. Check your cord with a volt ohm meter for continuity on the tip on one end to the tip on the other end. Do this for the sleeve on one end to the other. If you were getting the buzz without a cable it would mean that your input jack in your amp has a broken ground connection. Hope this helps.