@shuffy not knowing what has happened to your amp leaves a few possibilities. Blown power transformer bad screen resistor, blown diodes, blown preamp etc. you will have to do some checking and post images of what and where you check. Use [guide|21499|this guide] for that. It will allow us to see what you see. Let us know if your tubes glow orange or if they get bright red,. That would indicate a thermal runaway caused by a loss of the bias voltage. Power down with the amp in play mode (standby on ) and let it discharge for at least 15 minutes. Then use an ohmmeter and connect it from pin 4 of tube V4 to pin 4 of tube V5. You should get around 700ohm's resistance. If so your screen resistors are okay. Here is the schematic for your amp for you to check. [document|3192]