My mg 100 hdfx halfstack was playing at half volume then lost its volume

Yes you can as long as the speaker impedance when paralleled doesn't go below the rating of the amp. Marshall seems to hide their design lowest output impedance. Possibly you can find that in your owner's manual. Then find the impedance of the JBL. If half the JBL impedance is equal to or greater than the lowest impedance the Marshall is rated, you are fine to use it. The speaker Watt rating should always be bigger than the amp rating which it is in this case.

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.

For a test in troubleshooting, see if level from the headphone jack fades or not when this happens and get back to us.

The fuse is inside the unit so as to force you to open it and look for damage.

The fuse is likely a 3 amp/250 volt type.

Replace the fuse and then put a 100 Watt light bulb in series with the hot side of the power input. If the lamp stays lit with no load on the unit, then there is damage that requires repair before use. If you just replace the fuse repeatedly you may damage further components.

In the future obey the minimum resistance load on your amps.

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.

Yes. You can get them from Mouser electronics at $3.42 in singles.

http://mouser.com/Search/Refine.aspx?Keyword=TDA7293

It unfortunately sounds like a blown speaker. Try getting at the speaker and gently moving the cone with your fingers. If you feel a rubbing sensation you will most likely have to consider a new speaker. Make sure you get one with the same impedance (ohms) and the same or better power handling.

Hello

This will help you

http://www.guitartrader.com/!OL10BXPVIk3X3pt0Y2E!BQ!/Marshall-MG100HDFX-100-Watt-Amp-Head

Thanks & Regards

it could be your guitar pickups. try using another guitar or getting your pickups waxed at your local music store. also if your playing in a small room kind of loud, or if your using single coil pickups (like fender statocaster pickups) you will definitely get a feedback noise. if that does not work let me know.

try cleaning the send and return sockets with switch cleaner or WD40