Line 6 Spider II 212 problem

[RWP]

I just bought a Line 6 212 combo amp with known problems.  Only paid $60 with the intent of using its case and Celestion speakers as a 2x12 cab for a small tube amp.  However, I want to be sure there's not an obvious, fixable issue with the amp before trashing it.  I now have the speakers plugged into a jack mounted on the inside of the cabinet....immediately reversible as needed.

The seller accurately described the problem and I verified yesterday.  When powered up, the amp goes through what appears to be its normal startup selftest. All the LEDs work when knobs are turned, and all appears to be normal.  From what I understand this is the most frequent issue with these amps.  However, when a plug is inserted into the guitar input the amp begins a loud buzz/hum that is not affected by volume controls.  Stops immediately when plug is pulled.  I have not removed the amp from the cabinet and will look for anything obvious when I do (like a shorted plug socket).  Is there any typical malady that causes this problem? 

From past posts on this amp, it appears that the computer side of the amp is what fails, so someone may want the amp section to do some parts swapping.

I'm not inclined to put more money in this since the cost of a session with a tech will put this amp at its market value pretty quickly, but I'd be foolish not to check it out.  In any case, getting a nice open back 2x12 cab with Celestions for sixty bucks is a very good deal.

Thanks for any comments.

[J M Fahey]

I think the whole preamp is bad.
You don´t hear it all the time because it probably has some mute, activated with some pin of the input jack, so : no guitar-no buzz-no nthing.
Just in case, first resolder everything around the input jack, *maybe* some track or solder is cracked close to it, it´s very common for somebody to step on the guitar cable and break something, but if not, find the actual input pads for the power amp, which seems to be working well, and turn that amp into a loud, very good powered cabinet.
You can use it to reamp any small 15W practice amp to loud stage levels.
Many 15W beginner amps from good factories (Fender/Mrshall/Crate/Laney/Peavey) are very good, but lack power and speakers.

[RWP]

Good suggestion on a course of action.  I'm happy with the speakers since I have a small tube amp, but I'm not inclined to throw away something that could be salvaged.  Thanks.