PARISICC

Just so everyone looking at this knows, replacing the main board solved my problem too. I took the $92.40 gamble from fullcompass.com (not really a gamble since you can return the board) but it worked out. Amp seems to be back in business. Thanks to everyone above for the indirect help. To recap, I have a Spider III 120 and the amp would make a horrible squealing sound any time something touched the input jack. I wouldn't even have to fully insert a cable. This is also assuming the amp was turned on. Volume, gain, tone controls, etc, did nothing to the sound or volume of this squeal. I read these posts and fixed my amp. Quick rundown of how to replace the board...and sorry I forgot to take pics Parts required: P/N 50-02-9308-1 from fullcompass.com Tools required: phillips head screwdriver 2ea thin blade screwdrivers 15mm (?...forget the exact size I used...I brought a bunch with me from the garage) socket, and wrench if you desire box cutter, exacto knife Process: disconnect speaker wires. if you have more than one speaker, note positions/colors of each wire. you may also want to lay the amp/cab down on its face. unscrew 2ea (1 per side) mounting screws on either side of the amplifier assembly. these screws go through the cabinet into each side of the amp tray. unscrew the 4 screws holding the amp tray to the top of the cabinet. lift the amp assembly out of the cab use the 15mm socket to loosen and remove the nut on the front of the input jack. this will enable the input jack to slide out through the back. use whatever knife or cutting device you found to gently break the seal of hot glue that holds the smaller of the two electrical harnesses into the main board. pull that harness out by hand. use two thin-blade screwdrivers to put pressure on either side of the large ribbon cable harness and remove that harness. remove the 4 (or 5...i forget) screws holding the main board onto the amp assembly install the new board and use the reverse of this procedure to button the amp back up *the new board i received had a breakable tab/green section of extra board. You can run the wires from the smaller harness underneath and to the side of this tab so you don't have to break it off. I followed this method in case the main board was not the problem...then I would be able to return the board in original condition. ...and no, I didn't try to return my old board for a refund! Good luck all.

Also, Bob, I was curious as to how you figured out the troubleshooting process. Or could you explain how to do this or what terminals to check for 5V?

Hey everyone, My Spider III 120 combo has been squealing and I am probably going to try to replace the board as a couple of guys here seemed to have success with. Did any of you take videos of this to document the sound? Just to confirm, my amp turns on fine, I can switch channels, etc. The second that anything is inserted into the input jack (or even just makes contact), that horrible squealing comes. So I can literally just take one end of a cable and touch it to the inside of the jack to produce the sound. If I bear with the sound and plug the guitar in too, it doesn't matter...and I can't hear the guitar. Volume knobs, channel switching...nothing changes the volume or pitch of the sound. It seems like fullcompass.com has a return policy so I guess it's worth the ~$100 gamble, since all I would have to do is pay for return shipping and a restocking fee. Anyone have anything to say or add? Line 6 Tech Support is lame and a local certified technician/store wanted $60 to just look at it and said all his Line 6 customers are unhappy because stuff breaks and it's hard to diagnose...and then sometimes parts aren't even available.

I have had this amp for years with zero issues. Probably the last time I played on it was almost a year ago. I moved and it was transported lovingly, so I don't suspect anything was damaged that way. Here are my recent experiences from trying to play through it for the first time in awhile. First time I plugged in my guitar, there was nothing. Zero sound. I ruled out the cable and guitar being the problem, ended up playing on another amp I have, then decided to try the Spider again. This time I could hear the guitar normally, except about every 3-6 seconds there was a really loud "POP" sound that seemed to be the same volume regardless of the actual amp output volume. I believe i continued to hear this even with the guitar unplugged. Called Line 6 Support and they said to try a few things, including a factory reset, trying the headphone jack and then possibly taking the "amp" out of the speaker box to examine the input jack. Today I started to try these things and instead of popping or anything else, there is just a horrible squealing sound that, again, is loud regardless of amp output volume. The squealing came through both the speakers and the headphones and even occurred without a guitar plugged in. I'm guessing there is a problem with the board or other "intelligent" part. Has anyone experienced this? I saw one guy post something similar about his 75W amp and someone suggested that replacing the board for $90-$100 fixed the issue. Any help is appreciated and thanks in advance.