F-1X input hum

[jakebass]

Input 1 on my F-1X has developed a contact hum so when I plug into it there is a big amplified noise through the cab or PA. Is that something that a total novice could sort out or would you guys recommend getting it serviced? I don't know much about electronics but I'm pretty good at working things out in general terms. Any tips would be gratefully received. I could take some pics if that were helpful to anyone.
Thanks in anticipation.
Jake

[edwin]

Hm (no pun intended), it sounds like a bad cable perhaps. Have you tried different cables?
 
Another possibility is a dirty contact in one of the switches. Plugging a cable in and out a bunch of times can fix this.
 
Another possibility might be a loose ground wire in the preamp. Not very likely in my opinion, but possible.
 
Maybe a tube gone bad? I've not heard of this symptom, but I guess it's possible.
 
Something like this might seem like it's the preamp, but it could be a bad cable from the bass or between the preamp and power amp or even between the preamp and PA. If it has just started out of the blue, those are the first places I would look.
 
Edwin

[mica]

First, check if the nut holding the Input #1 has come a little loose. If so:
 
1. unplug unit and wait 15 minutes for the capacitance to dissipate.  
 
2. Take off the lid
 
3. hold the input jack #1 from the inside of the unit while tightening the nut on the outside.
 
4. Replace lid and test
 
Let me know if that clears up the problem.

[jakebass]

Many thanks Mica... Problem solved.
Jake