I have a Nady amp model xa-900 im working on. I need a schematic or service manual. I found it uses 4 each of kts301 thermostats. I found 1 open on each channel. I've replaced them but have both channels in protect mode. The +70 volt and -70 volts b+ is good in all collectors of output transistors. i have the +12 volts and +20 volt dc also. The pcb is labled +90 & -90 vdcom the rails reading +70 & -70. I would gladly pay for the schematic and cant find one anywhere. if anyone has it please contact me. Thanks Craig