Marshall JCM2000 TSL100 Noise Issue

[jar0ahr]

My Marshall tsl100 has a noise at idle that sounds like wind blowing across a michrophone wind screen. It was not noticable when playing. It seems to be getting worse now. When the amp sits idle and has a guitar plugged in is when it happens. Also, it seems to be almost non existant when the amp is on the clean channel. Most prominent in the two crunch modes and when a cord is in the input jack. Lately is starts to get louder and sounds like a short. It is beginning to affect output level and tone quality. It will settle down and stop at times. Should I start looking for a bad solder joint or a hot or loose connection somewhere? I will try to narrow it down to either the pre-amp or the output section, but I am open for any suggestions. The tubes are all new and biased correctly. It happened with the last set of tubes as well.


Thanks,

[Twist]

Look first for cold solder joints on 1/4" jacks, pots and sockets. I'm assuming you have ruled out noisy pre amp tubes also. Have you tried whacking the amp with your fist while it's making the noise? If it quits then it's most likely a bad solder joint or a dirty return jack on the effects loop. Another possibility is a bad plate resistor on one of the pre amp tubes and finally devices like OpAmps and small signal transistors can produce noise like you described.