marshall head trouble

[jeffinwv]

i have a jcm 900 dual master volume sl-x head


last night it starts breaking up when i strike a note..i kinda trys to come through....but it goes to static


i look at the tubes and all 4 el34 are lit and one small tube is lit...and the others have covers...



anyone have any ideas?

[izzybell2810]

Hi,

A tube that is lit doesn't mean that it's not faulty. The glow you can see is the heater filiments. Have you done the usual checks: patching effects loop send and return ect? The covers on the smaller pre amp tubes are removable. Just apply a little downward pressure and twist.

Dave.

[jeffinwv]

i put 4 new power tubes in it and swapped and tested the pre amp tubes and it didnt fix it....


i took my wooden chopstick and tapped everything in the chassis...there are no hot spots or spots that look bad...


it will play at a low volume and cracky then try to come in loud every once in a while but mostly its low and crackly