Question about Marshall Amplification Marshall MA100H and MA412 Half Stack

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My Marshall MA100H is blowing fuses

Every time i turn it on it blows a fuse idk what to dod

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Posted on Jan 02, 2017

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  • 5603 Answers

SOURCE: My Marshall 4502E Amp switches on fine. However

I would first check the filter electrolytic caps for shorts...

This is the WAY you work on this problem. Replace the fuse and put a 60 or 100 Watt incandescent lamp in series with the HOT power wire. This acts as a current limiter/automatic resetting fuse and you can search out where the current is going. Old trick we have used for more than 50 years. Also using a Variac to control the voltage can be useful, but the lamp should get you through the problem...

Posted on Feb 10, 2011

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SOURCE: I have the old 3520

Here is a link to your schematic:

http://elektrotanya.com/marshall_bass_200w_3520.pdf/download.html

Scroll way down and click on "Get Manual" link. They will only let you download two a day unless you are registered.

Suggestion is to troubleshoot and repair the unit.

You will likely find one of the following:

Shorted transistors in output TR5 through TR10

Shorted rectifier diode(s)

Shorted fillter capacitor

Shorted power transformer (not very likely)

Posted on Mar 21, 2011

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1 Answer

I have a Marshall ma100h that when boost is engaged hums incredibly loud. I've tried everything I can think of. The only thing to fix it is to turn the gain to zero.


I assume you've also made sure you're using a well sheilded intrument cable? If you're using a single coil pickup guitar like a Strat, you need to be sure you get the pickup cavity shielded. Past that it may be a bad tube in that gain stage.

Feb 06, 2015 | Marshall Amplification Marshall MA100H and...

1 Answer

Where is the fuse located in a marshall ma100 h amp head


The fuse should be located on the back panel near the power cord. However, there are also internal fuses as well....If the amp is vacuum tube you will also have a HT fuse as wall as a power fuse. If it is a solid state unit then it will have a power fuse.. Hope this helps.....If you need more info let me know....

Jan 16, 2014 | Marshall Amplification Marshall MA100H and...

1 Answer

Why my Marshall amplifier immediately blows fuses?


It could be a failed power supply capacitor, it could be a shorted speaker, it could be a shorted cable. It might also be a conductive piece of trash in just the wrong spot on the circuit. They would be the big ones of about 5000 microfarad give or take a few hundred microfarads.

Though a little less likely, there could be a short of failed component in the output stage.of the amp.

Sep 25, 2012 | Marshall MG100HDFX 100-Watt Amplifier Head

1 Answer

I got a Marshall MG100HDFX for free from a friend stating it was blown. I asked how this happened and he said that one of his friends plugged in another speaker or amp into the second speaker input in the...


The power amp section has blown parts. You will likely find they use a chip like the TDA7293 as the power amp output and it will be blown, shorted causing the fuse to blow. These cost $6 from Digikey.com. Find a competent tech to replace it and use heat sink compound. Verify the part before ordering one. They come with leads bent either way so make sure you get the one with a matching suffix letter. When firing up after repair, put a 60 watt light bulb in series with the hot power lead to act as a current limiter... saves blowing fuses if there is another problem.

Jun 21, 2011 | Marshall MG100HDFX 100-Watt Amplifier Head

1 Answer

My Marshall 4502E Amp switches on fine. However when you flick the STANDBY switch on it blows the 1.3A Fuse every time. Any solutions, baring in mind I have checked all the diodes, resisitors, rectifiers...


I would first check the filter electrolytic caps for shorts...

This is the WAY you work on this problem. Replace the fuse and put a 60 or 100 Watt incandescent lamp in series with the HOT power wire. This acts as a current limiter/automatic resetting fuse and you can search out where the current is going. Old trick we have used for more than 50 years. Also using a Variac to control the voltage can be useful, but the lamp should get you through the problem...

Feb 10, 2011 | Marshall Amplification Marshall MG250DFX...

1 Answer

Have marshall mg100 hdfx head -power it up and blows fuses right away!


This is either a shorted component in the power supply section or in the power amp electronics itself. Continuing to replace a fuse MAY damage additional components. Take unit in for servicing.

Nov 29, 2010 | Marshall MG100HDFX 100-Watt Amplifier Head

1 Answer

Marshall mg100dfx, internal fuse blowing every time you switch on the unit. What could be the problem


The way you troubleshoot this is to put a 150 watt lamp in series with the input power cord. The lamp acts as a resetable fuse and will limit the current while you look for the bad component. Start with the capacitors and rectifiers connected to the power transformer.

Sep 30, 2010 | Marshall Mg100dfx 100-Watt Combo Guitar...

1 Answer

Blown fuse


Continued replacement of fuses without fixing the reason for them blowing MAY be doing additional damage to components in the unit.

It needs to go to a repair shop. It is likely there is damage in the power supply section or that of the power amplifier section.

Feb 28, 2010 | Marshall MG100HDFX 100-Watt Amplifier Head

2 Answers

Hi im in Argentina and i accidentally pluged in my amp without an adapter now it doesnt work what needs to be fixd?


The power supply is blown. Argentina is 220V I believe. I have never seen a power supply schematic for this however being that it is low power it is a linear supply not switching. Either the rectifier diodes are blown out or possibly the output capacitors are blow due to approx double voltage. If you try this yourself be careful otherwise get a new amp. Good Luck

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