Rectifier Valve ? Many of the vintage amplifiers such as the Vox AC30 , Fender Twin Reverb  use a rectifier valve.  Other amps use modern silicon diodes. The rectifier valve  ( or diode) is a key part of your amplifier’s power supply. Its job is to “convert” or  rectify the AC voltage coming from the transformer into the high DC voltage needed by your valves in your amplifier. The output valves need the highest voltage […]
I thought this looked like a really useful table  on bias current for output valves. The top of the page allows the super  techie types to do an exact calculation based on measured voltages in your actual amp and the configuration of the circuit. The featured picture is actually all the tools ( apart  from the right screwdriver). It is simply a multi-meter and a special adapter. You plug the adapter into the output
What makes a valve fail in your amp Let’s have a light look at valves. Ever wondered why if you buy a nice new valve ( tube) amp that the amp has 2 years warranty and if you check the small print on the warranty carefully, you will see the valve warranty is a lot shorter – perhaps only 90 days! Valves are very old electronics technology. They were invented in 1910 and have been