20 Most Recent Marshall Amplification Marshall MG50FX 50 Watt Combo Guitar Amplifier with FX and MP3 Input Questions & Answers

Using the CORRECT footswitch for this model, you just plug it into the footswitch jack. You MUST use the correct one for the model.

If you are any kind of ab electronic bug you may be able to fix this. First of all if you can remove the main board out of this TV, do do. I must remind you, this will require patience and care. You better know exactly which wires you disconnect etc. With board at hand you will have to very, very critically inspect the board for bad grounds and resoder as necessary. The next thing to do is to check all capacitors with an ESR meter and replace the capacitors as you find. I would guess you have one bad capacitor. Ninety nine percent of the time resoldering grounds and replacing a cap will cure your problem. Thanks for asking and show all hands of support!

Many things can cause this... A COMMON problem is broken solder joints near potentiometer where they attach to the circuit board. Look for bad solder joints and also cracks in the circuit board.

This usually indicates that your neutral and live are backwards. Try plugging the unit into a different outlet elsewhere (different room)
If it still is buzzing, look for a GOUND LIFT switch in the back, it may have inadvertantly gotten flipped to the wrong position.

All amplifiers make a little bit of noise (hiss) but it is normally slight and drowned out by playing. However, assuming that this is not normal system hiss, here are a few simple steps to try and locate the source of the problem by process of elimination.

1. SAFETY FIRST - a common cause of a humming or buzzing sound can be a lack of earth (grounding) on the mains supply. With a 240volt AC supply this hum will be at 50hz (in the UK) - frequency may vary in other countries but should be similar. Check the earth first because of risk of electric shock. Until you are satisfied that this is not the cause of the problem DO NOT touch any metal parts of the amp. Remove the mains lead and try a different one. Try plugging the amp into a different mains outlet socket (preferably one on a completely different circuit).
2. Turn off other electrical equipment in the vicinity that may be causing interference. Move the amp a bit, try rotating it by 90 degrees to change relationship to things like mains electric cables in the floor.
3. If you are using the line-out socket to give a feed to a mixer, slave amp or p.a. system unplug this. Sometimes double earthing (through the mains lead of your amp AND the mains lead of the MIXER / PA) will cause an 'earth loop' due to a different resistance at each end. Putting a DI box with an 'earth lift' in between may eliminate this problem. Alternatively there are little gadgets you can buy to do this (I found one intended for car audio systems on Amazon that works very well)
4. Unplug any instrument leads - to eliminate possibilities of interference affecting cables, effects pedals or guitar pick-ups. Also unplug the foot-switch.
5. If that stops it plug a lead in without a guitar on the other end - does the noise return? If yes change the lead. If no plug the guitar in.
6. Try moving the guitar in relation to the amp (turn it around 90 or 180 degrees) - this will be pick-up to amp power supply interference.
7. Does the sound get better or worse if you touch metal parts of the guitar with your hand? This may be a screening issue within the lead or the guitar itself.
8. Try turning all the individual channel tone and gain controls to zero, turn off any effects on the amp panel. If that eliminates it only turn up the controls on channels that you are actually using.

https://www.dropbox.com/s/6spu98r39t2wvcr/Marshall%20G30RCD%20Schematic.pdf

First check the preamp valve in that curcuit

Hi. Doesn't look like it as the speaker is a 4 ohm one and the head needs at least 8 ohm as far as I can see.

https://www.manualslib.com/manual/99237/Marshall-Amplification-Mg15msii.html

Make sure speaker cable works and is connected then check fuses. If it has a master volume, make sure it's turned up.

Most likely cause for this is an intermittent potentiometer. Check to see if any of them are mechanically loose as this is a sign that they have been damaged and could have cracked the wiper surface inside the pot causing this problem. Alternatively, any switch that controls any gain setting could also be intermittent or dirty. Gain of the amplifier should be stable, but is controlled by the feedback and signal injection at the pots so that is where to look first. Good luck, as intermittent problems are tricky, but sometimes better than no function at all which can be more costly.

What type of Marshall, please? First of all, control the fuse and let me know.

clean switch connections

Does anything happen while you turn the knobs on the amp? I had a similar problem with a yamaha amp. It turned out a couple of knobs went bad. Soldered new pots and it works fine for me now.