Question about Marshall Amplification Marshall MG250DFX 100W Guitar Combo Amplifier

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Ive just purchased a marshall mg250dfx amp and when i play the volume cuts down low and then back up again like its fading in and out every so often

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Since you just purchased this, verify that your guitar and cables are good on another amp and if they are good, then exercise your warranty on the Marshall.

Connectors and cables for guitars are chronic problems so verify they are good to avoid looking foolish.

Posted on Jul 06, 2010

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I just repaired one. The 7293v output chips are bad, or overheating from a bad fan. They are cheap but must be de-soldered and removed from the output PC board, there are 2 of them (left - right). Its a difficult repair for a novice, have an electronics shop do the job.

Posted on Jun 23, 2013

  • don kuntze Jun 23, 2013

    I just repaired one. The 7293v output chips are bad, or overheating from a bad fan. They are cheap but must be de-soldered and removed from the output PC board, there are 2 of them (left - right). Its a difficult repair for a novice, have an electronics shop do the job.



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Low volume on my marshall

I am very new here and don't know how to answer a question to a specific problem so I will write about the most common problems that I have had over the decades doing guitar amp repairs. If you find that your amp is extremely low in volume and then suddenly comes back to normal- check out the effects return [or power amp in] jack. Especially in Marshall amps-these corrode and your signal dies. If there is loud noise such as hissing and crackling with no guitar patch cord in the input jack- the input jack is likely at fault. They normally have switching contacts that ground part of the input circuit when the 1/4 inch male plug is disconnected. When this in is corroded or too weak to make normal contact, you can get these symptoms. If your amp is a solid state Marshall or Fender and there is a random buzzing sound with no guitar signal connected- hit the side of the amp and listen for the buzz to go away or become louder-if it does, this usually means that the connections are loose at the two large filter capacitors. In one or more Marshall amps, they use a filter circuit in the low voltage power supple for the preamp tubes. If you encounter a dead Marshall[the model escapes me now] remove the circuit board and resolder the four connections at the bottom of the bridge rectifier. If you have any other amplifier repair questions you can email me direct at

Nov 14, 2011 | Marshall Mg100dfx 100-Watt Combo Guitar...

1 Answer

I've had my Marshall MG250DFX for around 7yrs now at it has been gigged regularly throughout that time. It's been reliable up until recently. I'm now finding that getting volume on the clean...

Well without testing a bunch of parts. I would say some component in the clean preamp has changed. It may have happened over time and now you are noticeing it. without checking all the parts it would be hard to tell. Get it to a service center. Or you may send it in to Pro Line Music

Jul 15, 2011 | Marshall Amplification Marshall MG250DFX...

1 Answer

When turning my Marshal MG250 DFX on, there is a terrible buzzing sound. I have tried it on different speakers and the buzzing still occurs. It does not change in volume when i adjust the volume. Whats the...

This is likely a filter capacitor issue. The right tool to troubleshoot is an oscilloscope. This could also be a failed power amp that is driving high DC current with ripple into your speaker. This can permanently damage the speaker. Repair this before using it.

Jan 13, 2011 | Marshall Amplification Marshall MG250DFX...

1 Answer

Whats best settings for blues on clean and classic on overdrive channel for the mg250dfx marshall playing a g&l s500

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Nov 08, 2010 | Music

3 Answers

Problem with marshall dfx250 just recently the volume on my amp is dropping and increasing at random, love the amp but needs fixed any ideas??

If you have no experience with amp repairs you are better off having it serviced. This problem seems to be related to bad solder joints in the FDD circuit exacerbated by the cooling fan aging and wearing out. Namely R107 and R96.

Mar 02, 2010 | Marshall Amplification Marshall MG250DFX...

1 Answer

I have marshall 250 dfx when i turn it on cooling fan makes weird noise then plays 10 min. amp starts fading in & out

Try carefully cleaning your cooling fan with qtips for the blades and a vacuumn. See if that helps the fan. If not it will need to be replaced. If you are experienced with amp repairs have a look for loose parts on the circuit board. If you can safely disassemble it, look at the soldered side for bad solder joints. From another poster on here with the same problem I have learned that resoldering R107 and R96 helped. Make sure they aren't burned out or have changed in value.They are in the FDD circuit. Have a look at your owners manual and it will make sense. The schematic is available here: If it doesn't come up use the search function on that site. Do not attempt to service this yourself unless you are absolutely sure you won't hurt yourself or the amp.

Mar 02, 2010 | Marshall Amplification Marshall MG250DFX...

3 Answers

Marshall MG250dfx's sound fades out

I have read that the problem is in the FX send/return jacks which oxidize if not used much. All you have to do, apparently, is ram a jack plug in and out a bunch of times. This breaks up the oxidation, and allows the amp to work properly again.

Feb 26, 2010 | Marshall Amplification Marshall MG250DFX...

2 Answers

Marshall DSL 100 - volume fades away and gradually comes back on

IF this is a vacuum tube unit, these symptoms are that of a tube that the heater is intermittent, that is it cools off due to a break and then liights again.

Open the back and observe the heaters in the tubes. DO NOT be fooled by some that have TWO heaters in them. (use a mirror if necessary) A single one that comes and goes can cause the problem and the voiration can make it come and go. This behavior in a tube is NOT somthing readily spotted in a tube checker. The delay in fading and coming back would be the delay in warm up following a heater going out and cooling.

Feb 14, 2010 | Marshall Amplification Marshall MG250DFX...

1 Answer

Left input for loudspeaker is dead? speakers both work out the left but neither on the right. can I fix it myself? marshall mg250dfx thanks

It sounds like the speaker output jack is broken or it has come unsoldered from the circuit board. You can fix this if you have enough electronics experience but you have to be very careful as components in an amp can carry a lethal charge even after being unplugged. You can partially discharge the capacitors by unplugging your amp from the power source with the speaker plugged into the working jack and set at a low volume while turned on ( not on standby ). If you feel at all uncomfortable attempting the repair yourself you are far better off taking it to a repair shop preferably one with experience with Marshalls. The same is true for other brands as well. Please let me know if this helps.

Nov 18, 2009 | Marshall Amplification Marshall MG250DFX...

1 Answer

Sound fades after 15-20 minutes

There may be thermal sensor that protects the power amp that is sensing over temperature and turning off the power amplifier stage.

Try cooling with a fan and see if it lasts longer. If you are obstructing the cooling in any way, try to avoid that.

As a test, leave on for an hour and THEN try driving sound. If it works for a while, then driving is what is overheating it.

VERIFY that you are NOT running too low impedance speakers!!!

Most amps will drive down to 4 ohms. That is a single 4 ohm speaker or two 8 ohms in parallel MAX.

Sep 09, 2009 | Marshall Amplification Marshall MG250DFX...

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