Question about Marshall MG100HDFX 100-Watt Amplifier Head

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I have an MG 100hdfx everything works fine till I plug in foot-switch, nothing happens when stepping on either switch. I've lifted the front of the head to about a 45' angle and the foot-switch activates Crunch with either switch as long as my foot remains on either of the switches, having that happen tells me something is loose but I'm not sure if its the jack or something else, also headphones do not work when plugged in and sound still comes from speakers, could they be coupled with the foot-switch problem?

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  • Bob Stato
    Bob Stato Apr 23, 2014

    Thanks Robert, I checked and the ground wire broke on the plug end of the footswitch, fixed that but I still have to hold down switch when I let off it will not hold and goes back to original channel, any ideas ?

  • Robert Jenkins Apr 24, 2014

    it sounds like, again, a severed wire. or the switch itself has gone bad. check the connections at the switch and the end where it plugs in

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  • 78 Answers

It sounds like something internal on the foot switch is shorting out (or a lead wire has come off) or some where in that line , it has been severed. you can check continuity with an ohm meter. butfirst open the foot switch and just give it a visual to see if any leads are severed. you may just need to solder it back. - foot pedals get alot of winding up and unwinding. its common for something to disconnect. that would explain all the issues your having. good luck

Posted on Apr 20, 2014

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Posted on Jan 02, 2017

bob_computer
  • 3153 Answers

SOURCE: marshall mg 100hdfx fan

Some of the Marshall equipment uses computer size fans and even on occasion the same connection.

Take the bad fan with you to a computer repair shop it will be much cheaper than a marshall part they should be able to help you out

Posted on Sep 09, 2009

Testimonial: "that sounds like the best way to do it..will just take fan to computer shop and try and get a replacement...thanks for the assistance"

  • 5603 Answers

SOURCE: by mistake i plugged the speaker jacks from

If you connected an external speaker plug from one into the same type plug on another amp, you have driven signals backward into the amp that was off... NOT into the speaker in that unit.

The usual result is blown parts in the amp that is off.

Some amps have their own speaker cable that you can unplug to connect to another amp and that is fairly safe. NEVER run an amp without a speaker load on it.

Posted on Feb 21, 2010

AndroidLVR
  • 31 Answers

SOURCE: Marshall MG50 DFX amp line out/headphones not working

Well, your problem isn't very descriptive to help troubleshoot online, but first question would be; are you using the correct size jack? The second would be have they worked before? If the answer is yes to both questions, then the problem might be the jack itself on your amp. There is a prong inside the headphone line that hugs the plug to your phones. If the prong has loosened enough where the connection is poor or not at all, you will not get any sound. If the headphone jack has NEVER worked before, than it sound like a wiring issue on your board somewhere. If you are not familiar with a soldering gun, then I would take your amp in to get it fixed. should be a minor quick fix costing anywhere between $15-$30 to have a shop do it. Hope this helps. (also try different headphones if you haven't already. Could be a bad pair)

Posted on Mar 09, 2010

  • 1 Answer

SOURCE: the fan on the back of my marshall mg 100HDFX is

You can either oil it up OR replace it for around 20$
Both ways involve removing the amp from the casing by unscrewing the 6 screws on top and sliding it out and then getting the fan out

locate the fan; locate the 4 outside screw covers that are next to the fan grill screws and pop them open. Remove the four screws that are under those plastic covers. The fan should separate. Take Fan out and remember how it was in there.
To oil: lift the sticker and locate the rubber plunger in the middle of the fan; remove it. Then, put ONE drop of regular 3-1oil NOT-wd-40, pb blaster or bike lube. re-assemble
To replace: just unplug old fan and then replace with new fan. I recommend replacing the fan when it gets to the point of bearing noise because oil doesn't always fix this.

Posted on Oct 06, 2010

  • 5603 Answers

SOURCE: I have a MG50DFX and

This is likely a bad switch contact in the headphone jack... they are really poor quality in most amps... plastic case and EASILY damaged by side forces on the jack. REplacement is the solution.

Posted on Nov 30, 2010

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