Looking for Spectral DMC20 preamp schematic

I have a Spectral DMC20 preamp that needs repair. It is from the late 80's and has worked well, but when I turned it on recently it appears to have fried a couple capacitors. Spectral won't send the schematic and they want $500 just to look at it once I ship to California (from Ohio). I have an experienced technician who can work on it but he needs the schematic. Any ideas?