Mods
If your amp is not doing what you'd like it to, sometimes it's best to modify your amp ownership rather than hacking into your amp. Unmodified amps are usually worth more, so you may want to undertake only the mods that can be completely removed.

Fender amps

• silverface vs blackface phase inverters
• Princeton Reverb: split load to long-tailled pair phase inverter
• Princeton: increase the headroom of the phase inverter (Stokes mod)
• Princeton: DC bias for phase inverter (Paul C mod)
• removing the pull-boost switch on some silverfaces

Master volumes

Power reduction

• triode converters
• pulling 2 of 4 power tubes
• power scaling
  • power scaling cascode

DC for heaters

Bias

• convert to cathode bias
• adjustable cathode bias
• convert to fixed bias
• bias switching
• dual bias supply

Maintenance

Bias
When you change power tubes, it's a good idea to check the bias. (You don't have to do this for preamp tubes.) Bias affects the tone of your amp.

• measuring bias
• calculating bias
• make a bias probe

Recapping an amp
Tweaking a SF deluxe Reverb
Layout of Fender Super Champ footswitch
Bassman 10
Replacing plastic jacks on Fenders

Where I get parts

Amp sites
The Fender amp field guide
Ampage
Blue guitar-Steve Ahola
Marshall Amp Schematics
Aiken amplification-Randall Aiken
Summit amps
Traynor amp schematic archive
Musicman schematics
Duncan's amps-Duncan Munro
Deltabluesman
Torres Engineering-Dan Torres