JCM 800 2205 Problem

[Jet Bycraft]

Hello everyone,

I'm having a problem with my JCM 800 2205. The amp does work, and it sounds good, however, when I switch it on, it produces a lo-fi rumbling/crackling sound. If I immediately turn it on standby, wait about thirty seconds, and then turn standby off, the rumbling/crackling sound disappears, and does not return until I turn it on the next day. Does anyone here know what causes this problem? Any help would be greatly appreciated. Thank you in advance.

 

[Jon Snell]

I would look for a noisy valve. As the heaters warm up, odd noises may emminate from a faulty valve.
Start with the output valves and work towards the pre amps.
Be carefull.
Dangerous voltages lurk within. Those angry pixies are itching to get out and do you some damage!

 

[Jet Bycraft]

Thank you for the information. I will check the valves.

 

[Crikey]

Un plug amp, clean all input/output jacks
Tighten footswitch jack on rear of amp
This is what was needed on mine

 

[XTRXTR]

Start simple eliminate the section of the amp its coming from. IMO easier to pull one small preamp tube at a time. You do not need to power off for preamp valve pulls, just keep MV off. Looking at the back of the amp left to right. If you pulled all of the preamp tubes and you still hear it, it is likely the Power valves or in the output section.

I have also had V2 issues with what sounds like a rumble or a low frequency white noise. It was microphonic. Clean the contacts of all the tube pin sockets with deoxit. Work a tube in and out a couple times.

Amp off, pull both the Power tubes, clean sockets same tubes back in, power on.

If still having issues come back and report what you did.