Question about Marshall MG100HDFX 100-Watt Amplifier Head

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How do I replace the power switch?

There is a black wire and a white wire with metal prongs at the ends how do I make this work there is no switch they are just laying there

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Take it in to get fixed

Posted on Jul 25, 2013


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How to fix the input plug on a Crate GX-15 guitar amp.

If u can bend the 2 prongs back towards plug end it. Will work on prong rides on tip of it the second rides in between the to nylon rings on it if that doesn't work any radio shack carry it for about 1-2 dollars

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Will amp still work after third prong is broke

If the third prong is the round one, then that is the ground to your amp. It will still work, however, the amplifier will not be properly grounded. So in a pinch you can use it, but you need to get the cable replaced. The ground wire is there for your safety, in case you plug your amp into a mis-wired outlet or if you are plugging in another instrument like a keyboard, mixer etc. that may be mis-wired. This could lead to a bad shock or worse. You have been warned.

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Solder the white wire to the shortest terminal and the ground/exposed wire to the outer/largest/ground terminal.

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The Fender pick up has two wires, blue and white. The Jackson has four: red, green ,black, and white.

1st. Determine the hot wire and the ground wire on the Jackson pick up and then just replace the Jackson pup with the Fender pup. White on the Fender is the hot lead and blue is for the ground. If you hook it up backwards it will be out of phase with the other pup's and will sound thin and weak when selected with either the rhythm pup or the lead pup. Of course, by itself it will sound normal because switching the wires only changes the phase of the Fender pup.
On the Jackson pup, the green and black are ground while the white and red are the hot side. Just solder the white lead of the Fender pup to the pup selector hot side and the blue lead to the ground.

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Peavey Rage 158 guitar amp

I don't believe there is a power "outlet" on this, only an "inlet".

Usually the inlet will have a lead, often green, that goes to the chassis.

There will usually be two other wires, often black and white that connect to the other two pins.

From the back of the connector, with the center pin tied to the grenn wire of the triangle lower, the pin to the right should be the white and the pin to the left is the black wire

Jul 24, 2010 | Peavey Kb2 1x10' Keyboard Amplifier

2 Answers

Fuse keeps blowing upon replacement in MG100DFX series amp. If the replacement fuse is correct, what else could be causing the fuse to blow?

The fuse blows because of a short in the Power Supply. The power transformers primary windings are probably shorted. next in the chain would be a bridge rectifier or a quad of diodes forming a bridge rectifier with a couple surge diodes off of the filter caps. so if you can disconnect the power from the amp, on the power tranny disconnect the primary wires ( the input AC power wires) usually white and black and take an OHM reading with a mulimeter accross the white and black wires. you should get a reading of 15 ohms or higher up to 30 or so. if so the primary windings are good. so then check the secondary (output windings) red and red yellow, etc. ohm reading and you should get a relatively low ohm reading 2-6 approx. if so its a good tranny. on the primary side if you get a real low reading for ohms , like 1 or something, its toast. once you rule out the tranny, switch your digital mulitmeter to read diodes (in the ohms area looks like a diode symbol (a line and a solid triangle with the line being at the tip end of the triangle). desolder one leg of the diode and put one probe on one side and the other probe on the other side. it should only ring out in one direction. you will be testing approx 6 diodes in this power grid on the pcb. you can also desolder the filter caps after you safely discharge the voltage with a 1 ohm 1 watt resistor to ground and use an analog volage meter to see the needle rise in one direction and not in the other (switching the test probes from one side to the other on the cap). usually what i do is just spend 20 bucks on all those parts from and instead of desoldering to test i desolder to replace with new. diodes usually part number 1N4003 or 1N4004 somewhere in that ballbark. hope that helps. i think its your power tranny primary winding that is shorted, be aware that this might domino effect into the rectifier and caps, so expect to replace them. its super easy!! you can email me from my website

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Sustain pedal on Yamaha DGX not working

I had the same problem, its to do with the polarity of the pedal. My pedal had a polarity switch on the bottom just flick this over and this should fix the problem. Otherwise another solution was to hold the pedal down and turn the keyboard on.

Jul 18, 2009 | Yamaha Full-Size Keyboard

1 Answer

Need to install new power cord

The black wire is in series with the power switch as it is hot. Use considerable care when working with A.C. If you are replacing cords, try to cut the wires off leaving some colored insulation so you know which is which. Always do these repairs with the power disconnected.

Apr 07, 2009 | Music

1 Answer

Changing the output Jack on 1985 Peavey Dyna Bass

If this has active circuitry, one of the wires is the cutoff for the power supply from the battery. The other two are black for ground and either white or red for signal.

Mar 13, 2009 | Peavey Music

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