Strange Hum on Sustainor

[dreamevil]

Hi.My sustainor has a strange hum problem that i couldn't figure out how to fix it. It makes it more when i use dist. (but it happens when its on clean too) When i first bought it, i replaced every elec caps and controlled every solders, cleaned the pcb etc.
I uploaded a video to show you how. After that strange noise came out i opened it again and found that when i touch that component(red circle on the photo) it happens.
Need your help!
Thanks.

VIDEO LINK
https://streamable.com/1luer

[Fireful0]

Sounds like maybe the red component thing you circled is coming unsoldered?

[dreamevil]

Thanks for the hint. I checked it, and solder looked ok. I don't know how and if it was broken.

[Fireful0]

Hmmm...
I wish I knew.

[GuitarBuilder]

What is the component number? I might find it on the schematic for you.

[dreamevil]

I just know the model 2N4338 but which one still don't. Q1,Q2 or Q7...

[GuitarBuilder]

Looks like Q1. Are you sure it's a 2N4338, not 2N4339?

[GuitarBuilder]

Also, did the hum exist before you replaced the caps?

[dreamevil]

There has been always a noise in my sustainor but this is different. When i touched that 2N4338 directly(when its pcb open) or even hit from upside of the sustainor box, hum occures.

[dreamevil]

Thank you so much. I'll try these steps as soon as possible. But on the other hand, i'm trying to find a 2N4338 Jfet replacement anyway.