I feel your pain! I bought an AG300 last year and it's the best sounding amp I've ever had for my style of play. It worked for 3 weeks and then failed to power up. I tried to contact Carvin and learned that they had gone belly-up the PREVIOUS DAY! I finally managed to get a response from them through a Carvin Facebook post that mentioned the stress they were under and asked me to be patient, but I've not been able to get any further response from them. I have exhausted every search avenue I could come up with to find a schematic. I have been buying Carvin products for more than 30 years and this has been a HUGE disappointment! There must be more of these AG300s out there that have failed and somewhere on the planet there must be some spare circuit boards for them or at least a schematic. A friend of mine who is a guitar-amp repair genius let my AG300 sit on his bench for several weeks but was completely stumped by the switching power supply design and returned it to me untouched. I am in non-profit work and unable to replace this amp so I am now amp-less. I keep hoping that someone somewhere will come up with a way to correct the problem with these temporarily great-sounding amps that have become $500 doorstops!