Marshal MG 100HDFX

[Grimaldo]

Sad story but Bought this half stack that works but when i push the clean/crunch button on the amp,it starts cutting out. Can anybody give me sum good advise what could b wrong. checked all the cords, an nothing looks burnt in side the amp and no severd resistors.

[Jazz P Bass]

So which section works correctly?
The Clean or the Crunch.
It sounds like you are saying that the clean works but when you push crunch the amp cuts out.

[acorkos]

i would start by spraying some deoxit on the switch and cycle it 10 times

[Grimaldo]

U no thats what it was doin at the time, but now it seems like the clean has half the volume wen i press the button from crunch 2 clean.. Another time before that it would almost seem it was the button it self, but the crunch would just fade out with no volume. Thank you so much 4 responding an i will get back 2 u when i can get a more precise issue with this thing.

[acorkos]

and spray clean the effects loop jacks, too

[mattball826]

inspect main board connections. marhshall ss amps notorious for bad ones. look specific at voltage regulators.
sometime i wiggle them and watch pad where they are soldered. look for breaks. you can confirm problem this way, but it can also be easier just to hit those connections with fresh solder. any 1-2 w or higher resistors, voltg reg's, electrolytic caps. speaking of ele caps. do the same to those. move them around and inspect leads are making good contact. if the move, there is part of another problem. add new solder to those.

check all signal circuit jacks too (not worry about speaker op jack). most of these are shorting type jacks. check resistance or continuity of each leg (gnd side and signal sides). make sure you read close to zero ohms. any higher reading means oxidized or dirty or open and that leads to many problems too. check all of them to be sure.

[Grimaldo]

Wait so check this out. found a broken sodr wire in the dfx side of foot switch. You think this might make a difference. i will solder an get back 2 you guys, evrybodys 2 sence very much apreciated!

[Grimaldo]

INput jack 4 the guitar also had bad solder point ,so i resodrd that as well an WALLA! the damn thing workn normally. ThankU Everybody an fortunetly This thing wasnt all that bad!!