Popping JCM 2000

[D28boy]

Hi

I got my JCM2000 DSL 100 serviced at Bletchley in March and it has just started to make a popping noise whilst I'm using it... It's fairly loud and only seems to happen just once 10 or 20 mins into a session....like the sorting of pop you get when switching off sometimes...

Any techies got any ideas or is it back to Marshall do you think...

[Mats A]

Have you tried changing valves? Most often a valve is the problem. My older JCM 2000 DSL had bad power valves and made many strange noises.

[D28boy]

all the valves were replaced at service

[sikter]

all the valves were replaced at service

It doeasn't mean they're all good. Some lasts many years, some lasts couple of hours ( or minutes)

[D28boy]

Would be a bit disappointed if Marshall installed valves failed in four months ! But hear what you're saying. However I would have expected to hear a change if were the case?

However have just phoned Marshall who said it could be an issue with house electrics and to try in another location to see if it happens there..so will try that first.

[Mats A]

Do so. But even Marshall can't tell if a valve is good or bad from the start.

[D28boy]

Thanx Mats...are you saying that the valves can function ok but still be "bad" ? Not sure I understand...or do you just mean that any valve could fail quickly because of a manufacturing fault for example.

[Mats A]

My amp worked but had lots of weird noises and pops. A valve can go bad quickly nobody knows before hand. But changing valves you need a bias check so take it to a tech or someone who knows. The DSL can quite easily be biased taking the metal back off without open up the chassi.

[Anitoli]

If the tube goes microphonic this is what happens. They start to make hissing or popping noises at random.
The only remedy is to replace the tubes, Or isolate the microphonic tube and replace that one. But that could be the cause of your problem.

[D28boy]

Thanx to all...I isolated the amp to a socket on its own (previously shared with another amp on an extenesion lead) and also now have my Boss ME-80 going into a different double wall socket which it now shares with my Bose I player docking station that I jam with. Played an hour and a half last night and no pops though as I said it only seem to happen the once a little way into my session.

[Mats A]

Great to hear. Rock on!