Amplifiers contain voltages high enough to Kill you even after the amp has been powered Off !!! If you don't have enough electronic experience to identify and discharge the Filter Capacitors which contain these Deadly voltages, take your amp to a Qualified tech. If you don't know a qualified tech in your area, post a request in the alt.guitar.amps newsgroup, the folks there will be happy to help you.
1. Replace the 250 pf disc cap in the preamp section with a Mica cap of the same value.
2. Replace the .047 ceramic cap in the preamp section with a .022 Polypropylene cap.
3. Replace the .1 ceramic cap in the preamp section with a .022 Polypropylene cap.