Problem with JCM900

[lateralus]

hey guys

i have a marshall 50watt JCM 900 stack, and lately its been having a few issues.

when i turn it on, the volume is about an eighth of what it should be, and after about half an hour it usually spontaneously kicks in to normal volume, blowing my head off in the process. Sometimes the volume never kicks in it all. I don't think its the tubes, because they were only replaced around 7 months ago, but im kinda hoping that it is, hopefully its not an expensive problem. Any ideas on whats wrong?

 

[ErikH]

Re: Problem with JCM900

Could be a bad pot, volume or the gain. Which model do you have? 4500, 2500 MkIII or 2500 SL-X?

It's best to let a tech check it out if you're no comfortable poking around inside the amp.

 

[lateralus]

Re: Problem with JCM900

its a 4500. I was thinking about taking it into a tech, but the guys round where i live charge like wounded bulls :laugh2:, but if i have to i will

 

[HolyDirt]

Re: Problem with JCM900

When the amp is on, what do the tubes looks like (color of glowing, brightness of glowing.. etc...)?

 

[lateralus]

Re: Problem with JCM900

light orange, they dont actually look any different than normal. Theyre sovtek 6L6's if that helps

 

[HolyDirt]

Re: Problem with JCM900

light orange, they dont actually look any different than normal. Theyre sovtek 6L6's if that helps

Sounds like it could be a number of bad things inside the amp... if you don't know how to work inside an amp, take it to a tech! Best to be safe.

 

[Jeff Seal]

Re: Problem with JCM900

Try this.... in the back of the amp there is an effects send and return. take a short cable and jumper them together. Also turn the control for effects level (next to the jacks) up and down about ten times and see if any of this solves the problem.

Jeff Seal