I love this series! I have several of them, but this book is a good beginning!

Want to know about tube amps and how to modify them? I have this book and it is excellent! There is tons of information on tube amp circuitry, this is a must-have if you want to learn about tube amps.

My Fender Bassman was showing zero current at idle on one of the two 6L6GC tubes. I knew it was isolated to the socket because swapping the tubes showed the same zero current on the same socket. To make a long story short, the screen resistor (470 ohm) was fried. This is a 1 watt 470 ohm resistor that goes across pins 4 and 6 on the output tubes. The real culprit was a bad tube that would draw too much current.
Replaced the screen resistor and tube and all is good.

The symptoms of the bad tube/burnt screen resistor was low output volume and extremely low/none current across the 1 ohm cathode resistor.

Here’s an old article I wrote for beginners to understand tubes a little more – coming from a stompbox perspective:
Tubes for dummies

Looking to repair your old Fender amp?
This site has a ton of schematics and layouts and they are cleaned up.
Nice site!

Vintage Fender Amp Repair

Very interesting use of foam to help prevent “beaming” of speakers.

Check it out.

as used in Tube Amps. Check it out.

A great Music Electronics Forum thread on power supply capacitors for your amp. I used the balancing resistors on my 64′ Fender amp and it has worked great!