If another reverb tank worked in your amp you do at least know that it's definitely the tank.
If the wires look connected you're as well just replacing it probably - either the drive coil is blown (not the return if it makes a noise when shaken) or there's a break in the fine wire or solder connection at the coil. I just repaired one exactly like that today, but it was a real pain - it would have been cheaper in hourly rate to just replace the tank probably, but I didn't have a spare one to hand and I did have the time, so I fixed it. Not recommended if you're not experienced at these things.
I'm not certain of the right spec for a JCM900 - it's a solid-state-driven reverb, so it may well be different from the usual tube-type ones. Simplest is probably just to call a Marshall service agent and see if they will get you one.
I just bought a Fender super champ tolex. Don't know what year yet still researching. I do need the input transducer on the reverb tank or a new tank. Please help
If another reverb tank worked in your amp you do at least know that it's definitely the tank.
If the wires look connected you're as well just replacing it probably - either the drive coil is blown (not the return if it makes a noise when shaken) or there's a break in the fine wire or solder connection at the coil. I just repaired one exactly like that today, but it was a real pain - it would have been cheaper in hourly rate to just replace the tank probably, but I didn't have a spare one to hand and I did have the time, so I fixed it. Not recommended if you're not experienced at these things.
I'm not certain of the right spec for a JCM900 - it's a solid-state-driven reverb, so it may well be different from the usual tube-type ones. Simplest is probably just to call a Marshall service agent and see if they will get you one.