Question about Marshall Mg100dfx 100-Watt Combo Guitar Amplifier

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Marshall Mg 100DFX power on no sound it just cut out last time i played it.The fan has issues I wonder if there is a cooling sensor shutting down the amp output.I thought solid state amps were bullet proof.

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If you put in headphones in the amp headphone output, and there's a sound, it's probably the output amp (IC1 - TDA7293V) that's bad from the fan failure, if not cooled proberly failure is doomed to happen. Replace fan and output part, and you should have an amp up and running again.

Posted on Nov 17, 2011

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Something has probably failed or become a bad joint. If you turn up the gains and volume to max is there any hiss or hum from the speaker? If not there will be a problem in the power amp or power supply. Check fuses at back. The speaker may be open circuit too, that is easy to check with a multimeter. If you can't get far yourself, you'll need a repairman.

Solid state amps are not that reliable these days, there are so many things that can fail due to all the effects that people demand to be built in. Look at how many people are reporting problems with ss amps here.

Posted on Apr 02, 2011

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1 Answer

Only just bought amp ,but twice now its just cut out,lost sound ,if i switch off wait a minute it ciomes back on cannot be normal surely? rgds neil


Not normal... however verify your guitar cable and guitar to avoid embarassment if the problem might be with those items. ALSO if you are driving this too hard, it probably has thermal shutdown and will shut down the power amp if the circuits get too hot... This is a smaller amp so If you are playing louder than *********** could stand it in a 15 foot square room, you are overdriving this unit and you best get a bigger one.

Aug 07, 2011 | Marshall Amplification *new* Marshall...

1 Answer

My Marshall Haze 40 Amp started making a very loud humming noise after a couple hours of playing.I let it cool down,and turned it back on and the noise came back after a few minutes


may be one of the electrolytic capacitors in the power supply has become leaky...this is a common problem among amplifiers...so you let it cool down..then after a period of time the capacitor heats up and then causes the hum...the power supply caps filter out the 60 hertz ac line noise...which is probably the frequency of the sound it is making...this is a good indication of these caps going bad....another thing you can check is to see if the amp is properly grounded(eg: the ground pin on the plug is present) and that you dont have an open cord or input

Jul 10, 2011 | Marshall Amplification Marshall Haze 40...

1 Answer

Hi i am john... i have a 100dfx mg series... it is


There are MANY more likely components than the transformer that will cause the fuse to blow.

Most common are filter capacitors, rectifier diodes, and shorted components in the power amp section.

Transformer failure is very UN-likely. Have a competent electronic tech troubleshoot the unit.

When testing the unit, put a 150 watt light bulb in series with the power line... saves fuses during troubleshooting. This limits the current so one can analyze the real cause of the problem.

Jul 12, 2010 | Marshall Mg100dfx 100-Watt Combo Guitar...

1 Answer

I was playing my Marshal 100DFX for about half an hour and when I was done it smelled like burnt electronics. Then I noticed the fan wasn't working. It usually turns on right when I turn the power on. I...


Replace the fan with an IDENTICAL part. Do this before using the unit again.

There is a possibility that the fan is controlled by temperature and the failure is actually with that electronics rather than the fan itself.

May 19, 2010 | Marshall Mg100dfx 100-Watt Combo Guitar...

1 Answer

IS IT HARD TO REPLACE COOLING FAN .MG 100 HDFX?


Hardest thing is getting the chassis out past the Tolex covering. Sometimes it catches and you have to use a knife blade to hold it out of the way.

Make sure to use an identical fan with identical ratings. Some of these are throttled depending on sensed heat. For those, an exact model fan should be used.

May 09, 2010 | Marshall MG100HDFX 100-Watt Amplifier Head

3 Answers

Buzzing fan on a Marshall mg 100 head


Try to remove the fan and look for the sticker on the back side where the wires come out.

Remove the sticker, underneath it there will be a small aluminium cap (sometimes there is no cap and the axis is readily visible when you remove the sticker).

Take the cap off with a sharp tool (it shouldn't require a lot of force to do it), now you should be able to see the fan axis being held in place by a small clamp - put a drop or two of machine oil in there, move the fan blades a little to make the oil flow past the axis into the bearing.

Reinstall the cap, put the sticker back in place, reinstall the fan and test it.

Sometimes this will make things better, but if it doesn't then it is only fair to replace the fan.

regards

Triarcuate

Sep 25, 2009 | Marshall Mg100dfx 100-Watt Combo Guitar...

2 Answers

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

Sep 09, 2009 | Marshall MG100HDFX 100-Watt Amplifier Head

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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