I just had a a (Korg) Vox Cambridge 15 roll into the shop, but do not have a schematic or service manual for this specific unit. It has very low output and the clean channel is pretty distorted....unless the tremolo trim pots are tweaked, then the amp comes alive for a few minutes and then back to crud it goes. I'm leaning on the thought that the vactrol is shoddy, but would love a schematic/service manual or input.