On the MG30FX, it wont stay in overdrive sometimes. I push the switch in, then it will go back to clean automatically.

replace fan

Hi J Wade. I'm Dave P. I'm not a guitar amp expert or technician but I've been using amps and effects for 35 years and there are a couple things I can suggest.

That kind of periodic noise/switch noise can be a symptom of having the polarity of the amp reversed. If your amp has a 3-position OFF/ground switch, try reversing the ground. If it doesn't, take the plug and turn it around. Just don't get near a microphone unless you're sure your amp is grounded the same as the P.A. It could fry your lips off.

Dirty switches to that too. You said the noise is in time with the delay's tap time which is set by a foot switch. If tapping that switch the first time generates a pop, the delay may have catch it and is repeating it. Turn off the amp, remove the delay foot switch and turn it back on. Still noisy? If not, give the foot switch a good cleaning.

When you turn the EFFECTS knob up, is it scratchy? Might need the potentiometer cleaned. What happens when you specifically turn the DELAY level down all the way while using the other effects? Noise still there?

That's all I've got. Hopefully, it was helpful. Don't wrack your brain over this too much. There could very well be an internal problem with your amp that will require a trip to the shop. You don't want to open it up yourself. Rock on but be safe.

Dave P.

This is because your clean channel only runs through the pre-amp section, requiring an increased volume level to match that of the volume of the drive section which is overdriven by the pre-amp circuit. my suggestion is to use lower volume level on the clean channel of the amp. To get any volume boost you may need to match the two channels you could use a signal/volume booster or overdrive pedal between your guitar and amp input, switching it off and back on when you switch back and forth between channels.

Often the boards will be the same, but the power transformer MAY have higher voltage. Also you have to be careful as the speaker might NOT take more power. If you need more power, get a bigger amp. A lot of the smaller amps use the TDA2050 chip which can generate a max of 32 Watts RMS. The bigger Marshall's 50DFX use the TDA7293 or a pair of them which is a different animal entirely.

Likely either a rectifier diode, a filter capacitor, or the power amp transistor or chip/stick have shorted and failed. Unless you are electronically adept, it is time to take it to the shop as the cause of the failure will not fix itself. DO NOT replace the fuse as additional damage may occur..

Sounds like the overdrive switch needs cleaning (with switchcleaner) or replacing. Try touching the switch gently when in overdrive position - if that brings on the jump-to-clean fault, then you confirm the switch is the problem.

A possible problem MIGHT be marginal switch contacts on the external foot controller cable. If you are not using the foot pedal, these contacts must maintain contact to keep the same channel selected.

IF YOU ARE USING the footswitch, then likely problem is with cable and or the pug and jack.

IF YOU ARE NOT using the footswitch the contact switch on the jack for the footswitch is PROBABLY intermitent contact. These jacks are POOR quality in the music equipment. If this is the case in yours, open the unit and tighten the spring contact.

have you tried the footswitch to change channels. also. my amp has to be in channel 2 position (with the button on the head) before i can use the footswitch. sometimes the input/footswitch jack wears out and you need to bend the internal tip/ring tabs of the jack to make better contact. also like on my fender amp, i had just a standard mono instrument cable going to my footswitch and it was acting wierd cause it needed a stereo instrument cable. one last thing on the grounding resistors on the pcb, they get hot and break the solder welds which messes with all sorts of stuff in amps. usually look like sugar cubes , cement resistor. 5watt usually under 1k ohm. check for bad solder welds on the pcb where the big resistors are and the switches/buttons and at the footswitch. there may be a bad ic or transistor for the channel swithing