WARNING: Never attempt to open up your tube amp chassis or repair/modify it in any way, as lethal voltages may still be present for extended periods after the amp has been turned off and unplugged from the AC wall socket. Instead, take your amp to a qualified technician for inspection or servicing.
PLEASE NOTE: The following links and resources are provided strictly as items of theoretical interest only. I have no control over, or responsibility for, any third-party websites or material referred to.
If you’re interested in tube amp theory and design considerations, then you might like to check out the “Amp Books” website. While it’s primarily a vehicle for promoting Richard Kuehnel’s books, it also features a swag of interactive goodies and analyses including: “[online circuit] Calculators, Tutorials, Technology, and Classic Vacuum Tube Designs for Guitar Amplifier Circuits.” What I like about this site is its clear, methodical, modular approach to classic circuit analysis.