Urgent problem! Marshall Valve content.

[girlafraid]

I've got a Marshall JCM 600 2x12 combo and it isnt making any noise!
I recently replaced all the valves, which needed doing. I used it for one band rehearsal and left it at the space, which a couple of other bands we know use too. After a couple of weeks holiday, I return and find it doesnt work, which seemed to be because of a blown fuse. I replaced all the fuses, with the right components. However, the fuse just blew again. Its the one right under the power valves, behind the capacitors.
The really scary thing is that none of the valves are lighting up or getting warm... I have no idea who has used the amp, or how, but at the moment I'd be imensly greatful if anyone could tell me what appears to have happened, and more importantly, what I can do to fix it! thanks.

 

[STRATDELUXER97]

Re: Urgent problem! Marshall Valve content.

Does it have both an HT fuse and a mains fuse like older Marshalls? Can you get the chassis out and look inside for signs of discoloration,charring around a component,tubes,etc? Best to peak inside and look for the obvious rather than putting new tubes and fuses into your amp....

Does the pilot light come on and you say the heaters for the tubes don't light now right? That's a mains PT problem maybe?

Check your mains fuse first and get inside that amp and look and smell inside there for obvious signs of something gone wrong...Make sure the amp is unplugged and don't touch any of the components inside of your amp so you don't get shocked....

If you do see something,maybe you can post a picture here on the forums for further guidance?

 

[girlafraid]

Re: Urgent problem! Marshall Valve content.

thanks very much for your prompt reply!

ON EDIT.
the mains fuse is fine. there are two other fuses inside, one of which keeps blowing. One of them blew before when one of my power amp tubes was cracked.

I havn't actually had the amp biased yet, and as such havn't really used it since putting the new tubes in, so do you think that it could all be down to this? I'm beggining to think it was used in my absence, whioch Im not all too happy about right now.

Im afraid Im a bit of a newcomer to this sort of thing, I know a little about the basics and how to keep safe though! thanks.

 

[STRATDELUXER97]

Re: Urgent problem! Marshall Valve content.

thanks very much for your prompt reply!

ON EDIT.
the mains fuse is fine. there are two other fuses inside, one of which keeps blowing. One of them blew before when one of my power amp tubes was cracked.

I havn't actually had the amp biased yet, and as such havn't really used it since putting the new tubes in, so do you think that it could all be down to this? I'm beggining to think it was used in my absence, whioch Im not all too happy about right now.

Im afraid Im a bit of a newcomer to this sort of thing, I know a little about the basics and how to keep safe though! thanks.

Might be best to get it to a local "competent" tech? That's your safest bet..

 

[girlafraid]

Re: Urgent problem! Marshall Valve content.

Thanks for your help. At least its prompted me to do a bit more research into these sort of things. One day I'd like to be able to service all my gear myself... may be some time....

 

[Inferno]

Re: Urgent problem! Marshall Valve content.

Hey, I have a JCM 600 head and a while back the same thing happened to me. The amp powered up, but there was no glow coming from any of the tubes and I was getting no sound. I took the amp apart and spotted a blown fuse. Once I replaced it, the amp worked fine.

Now, if your amp is blowing fuses often, let that be a warning that something much more serious is wrong.... :reporter: