Ibanez FL-9 (original) noise issue

[qb]

Hi,

I am trying to fix my vintage (I bought in 80') Ibanez FL-9 which has annoying white noise either when is on or off. The noise only comes when I use 9v DC supply. With a battery, it doesn't. I replaced 9v 2.1mm DC power plug but it doesn't change. 

Is there anybody who can suggest what I should do to fix this please?

Thank you in advance

[aron]

Isolate it with a new power supply. Make sure that the new power supply is 9V regulated.

[qb]

Thank you for the reply. Mine is on the board with regulated 9v power supply unit. I taken it out of my board and use the 9v supply it still has the noise but with battery it doesn't. So, isolating is not the solution? I do not have a clue at this moment....

Regards

[duckpow]

What about cheking the Voltage of the battery?
If it only hums when a power supply is giving 9 volts, and not with a battery that maybe only supplying 7.5-8.5 volts...

[qb]

Thank you. I will check it later. But another funny  symptom is it does not have white noise when I use a clean channel of my Marshall but it has strong white noise with dirt channel (although the output volume I hear is the same level to my ear).....   

[aron]

Did you try another power supply? When run with the battery you mean it has no white noise at all - overdrive channel or not?

[qb]

I tried a different power supply but the issue is the same. With battery, there is a noise but far less.
The noise is a kind of white noise but there is a slight signal like tone included. It is amplified when distortion channel is used although the guitar sound is almost equat in a clean channel. I suspect power is leaking into sound signal or earth/grounding issue???

Regards