Marshall MG100HCFX

[ahseng]

Hello all,

I have this Marshall MG100HCFX Head version in for repairs. I was told it has a cracking volume. Tested it with headphone and confirm. Sprayed it then try to test with headphone and a speaker from another amp. No positive result. I just noticed a fan inside facing downward. I did not see this prior. My questions are.

Is the fan suppose to spin from start up?

Is it safe to power up without speaker load?

Can I connect only one 8 ohm load at one of the speaker out? Or must I use two?

With some schematics it could be comprehending to be sure where the signal path are for me to scope around since I opened the amp.

Thank you kind folks.

[vintagekiki]

doesn't promise much but ...

https://music-electronics-forum.com/forum/schematic-requests/50366-request-marshall-mg100hcfx-schematic

contact doctor (pm)

[alexradium]

Hello all,

I have this Marshall MG100HCFX Head version in for repairs. I was told it has a cracking volume. Tested it with headphone and confirm. Sprayed it then try to test with headphone and a speaker from another amp. No positive result. I just noticed a fan inside facing downward. I did not see this prior. My questions are.

Is the fan suppose to spin from start up?

Is it safe to power up without speaker load?

Can I connect only one 8 ohm load at one of the speaker out? Or must I use two?

With some schematics it could be comprehending to be sure where the signal path are for me to scope around since I opened the amp.

Thank you kind folks.

fan should spin when the temperature gets very hot on the power amp,at idle in normal condition it never starts.
yes ,transistor amps don't need a load.
this amp is a real pain,because of all the programming features they added,ruining both sound and reliability.

[J M Fahey]

I bet fan/heatsink designer "other job" is designing motherboards.