I recently bought a used spider 3 120w amp and after a few months it started acting up. first it started switching channels on its own until it warmed up (10-15mins). after a while the modeling knob stopped working although it is does not appear to be broken. the led`s still light up when i switch the preset channels but the knob itself wont change them. i was told they are battery powered. is this true. it gradually got worse, going from a lag to not working at all

Hi, Sounds like you have a bad cable to your amp. Try swapping out the cable. If that is not the problem, The pickup maybe bad.
Hope that helps.

I have same problem. i have this map. please help me to find the problem. if you can point the area in this map that problem is from that.

I had the same issue with my AS100D. When I first bought it the treble knob on the top channel was very responsive. At 10 is was unbearably "trebley". I was getting plenty of "high" treble set at 2:00, even 1:00. Then after about 6-7 mo, I started to feel it the brightness was leaving the amp. I was now putting my treble knob all the way to 10 and keeping it there, and it still wasn't enough. I had it serviced twice, no solution. Marshall got into the act and after months of going back and forth, they finally replaced the whole amp with a new one. I just got it. The treble was incredibly bright at 10, just like the former unit. But now after just a couple of days, I can already see the treble knob is not as responsive. I can't believe it! Now what?

Bad soldering, especially around the jacks and plugs. Crack in the circuit board. Bad switch contacts on the headphone jack... all these are first things to check.
Here is your service manual for the unit:

http://elektrotanya.com/line6_spider_15w_ii3012_1508_sm.pdf/download.html

When it is working, wiggle the channel volume control WITHOUT rotating. If the sound cuts out, likely the soldering of the pot leads is broken where it attaches to the board. Try resoldering the connections.

SOMETIMES the control is damaged in which case it must be replaced.

Poor contacts at jacks can cause this... it results in the contacts acting like a small capacitor passing only the high frequencies at very low level.

Power amp inout jacks are notorious with switch contacts that pass the preamp signal to the power amp if the power amp input isn't used.

There are many other possibilities and only hands on troubleshooting will determine the cause.

Acoording to the manual hold the tap button for a few seconds and the tuner will come up in the LCD display. Here is manual in pdf form...

http://line6.com/data/l/0a060072ba114a95b315b526f/application/pdf/Spider%20IV%20Advanced%20Guide%20%28Rev%20A%29%20-%20English.pdf

If you have the manual try doing a factory reset. The info is here:http://line6.com/community/docs/DOC-4499 You might also be interested in joining this forum:http://line6.com/community/community/support/amplifiers/spider?view=discussions

The bypass switch in the headphone jack is likely broken. NEVER unplug the headphones while the amp is on.

There are certain small amps that have a possibilty of popping the power amp due to a feedback arrangement. Likewise, never use the headphone jack for ANYTHING other than headphones.

Sounds like your master volume is turned up too much. The channel volume will make the squealing go away(caused by high gain and humbuckers). The best thing to do is dial in your favorite presets and change the channel volume to the correct level with the master volume where you usually keep it. I use my Spider Valve at master volume at about noon and the channel volume between nine o'clock and noon. Let me know if this does not solve the problem......