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Marshall mg30 dfx onboard effect don`t work

I have a mg30 marshall amp with digital effects but they don`t work.the two channels(clean and distorted)work fine,no unwanted noises but just the effects problem.any idea?

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  • Anonymous Mar 23, 2009

    i have the same problem.it happend when i hipped my amp from india to europe(i used to live there)

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5 Suggested Answers

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SOURCE: Crate VC6212 Amp

Yes the tube could be what is called microphonic. In other words it behaves like a mic and feeds some signal back into the amp. These are usually 12ax7 tubes and are not expensive. Start with replacing that tube.
Keep us posted.
Dan

Posted on Apr 07, 2008

  • 5603 Answers

SOURCE: Marshall MG50 DFX makes a squealing noise on power up

Yep, chalk that one up to poor design...The amplifiers are going out of balance during power up and down. Two seconds is pretty long... Try turning down the gain during power on and see if that affects it.

The pop on turning off is normal... None of these have speaker disconnecting hardware that is necessary for very high power amps. The biggies have hardware that checks amplifier is balanced before connecting the speakers and a relay also cuts the speakers immediatley on power down. As power goes up and down the circuitry comes to equilibrium and until it does, strange things happen.

I would investigate the CONDITION of the filter caps for the main power because if they age to a higher internal resistance that COULD cause the high freq oscillation on power up... Two seconds is MUCH too long.

There should also be some non-electrolytic caps NEAR the power output transistors to handle high frequency supply power bypassing.

Check the power bypasses that service the preamp stages. Look for pregnant electrolytic caps that have failed.

Ultimately, you MAY need an oscilloscope to isolate the high freq problem.

Posted on Jan 03, 2010

Testimonial: "Thanks - great advise! The gain position makes no difference. I'll try to chase the problem with my Tek Oscilloscope ;-)"

  • 506 Answers

SOURCE: Amp sound fuzzy and out of tone.

Well if you want goo dpinch harmonics to squeal you need a decent amount of gain and good pickups. What guitar are you using, some lower model passive pickups have bad frequency response when you try to do pinch harmonics. If you have decent pickups I would say get a higher gain preamp and just run the amp on the clean channel. There a re tube preamp pedals out there that have masaive amounts of gain and they are reasonably priced. There are also so good amps out there for a decent price like the 6550 from peavey. I have a 5150 block letter and that thing can produce good pinch harmonics along with my EMGs. Good luck man, oh and there is nothing wrong with your amp, it is just time to move on. There is only so much you can do with solid state amplifiers in my opinion.

Posted on Jan 13, 2010

  • 5603 Answers

SOURCE: Marshall MG50 DFX, the volume knob OD channel crackles

Either the control is damaged (happens if they get hit) or it is possible the circuit board it is mounted on has broken solder OR worse, a crack near the control. The unit will require servicing. Parts are readily available.

Posted on Jan 31, 2010

  • 88 Answers

SOURCE: my marshall mg100hdfx digital fx rack wont work

sounds like the effects module has stopped working . you could try re-working the joints around the i.cs on that board if you have a rework station. i have only managed to repair one baord this way suggest replacement is the best course of action. uk cost of panel approx £50.00 + fitting

Posted on Feb 04, 2010

Testimonial: "helpful and realistic advice"

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Turn off the effects or go inside and unplug the little sound card. It is only a few samples of real effects, not the real thing. It's like a cheap PC sound card separate from the other components and has a small power plug on it. Wiggle that plug or unplug to see if it changes. It won't cut her sound, just the effects. Make sure the effects are off and verify, if using a footswitch, that it is working properly.

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The P803 is designed to work with the "Valvestate" and Tube amps. I don't think it is compatible with the Haze40 since they have an optional 4 button footswitch so the optional one would necessitate different interface than the P803.

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Good day!


You button on channel is not back to the original position (n.o) normally open.That is the effect when the button is defective replace it immediately.

Thank you and don't forget to rate my answer.

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1 Answer

Hi,I turned on my Marshall mg series 100 dfx and there is no sound,just static comes on.Its starts with a kinda bad feedback sound than turns to loud static.


I suspect the power supply for the effects processor has failed. The effects unit will "go crazy" when power supply is too low voltage.

If the amp has loud noise, then the power amp portion is PROBABLY OK.

I had a similar problem in a Behringer amp caused by a bad electrolytic filter cap.

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