Fender Bassman 300 Troubleshooting and How to Bias Tubes

Here's another repair blog episode.
GWAR is in the studio working on a new record and this bass amplifier popped it's mains fuse during tracking so I wanted to get this amp working again fast so it could get back to work. Luckily it only needed new output tubes and to verify the problem was indeed the tubes I put them in a tester to look for any obvious faults.
To bias these amps they must be set to 80mV (some models may require 100mV) and you take the readings from a convenient test point located in the back of the amp. Once you have set your bias you then must balance the two sides. A very simple procedure and it is very nice feature to be able to do this without pulling the chassis from the headbox.
This is the same amplifier as the Sunn 300T.
I really dig the way this amp sounds. Hope you enjoy.

[@carsonburmester3179]

All hail the next Lemmy🤘🤘

[@charliepresley]

Had the same thing happen to my Bassman 300pro. New tubes and it was good to go!

[@jackgraham5037]

Sounds so good. Ripper playing.

[@russiangoose7053]

Shoulda plugged a guitar into it haha

[@jupitermoongauge4055]

As a tube amp nerd I'm loving this channel. but dude, I have to ask, are you Jim Morrisons grandson ?

[@joeldiresta8109]

Sunn it Doom

[@1badass1985]

Siiick

[@shag377]

I still wonder when you manage to sleep between everything you have going on ...

[@andrewbrewer3050]

Fuck yes!!

[@robertocantu792]

I have 2 Sunn 300T's and on one of them the red green led doesn't light red when the amp is turned on. It will light green when i flip the stand by switch. The other 300t works just fine. What could be ny problem? YOU TUBE has nothing on this. Any suggestions would be greatly appreciated.

[@xfredoux]

Hey quick question! Wondering why we absolutely want a matched set of tubes and want it even means

[@purgasound]

The short answer is that you want them to all function equally to get the best response from the amp. Every tube draws a different amount of current and while slight mismatches are not noticeable, large mismatches can attribute to poor sound quality and uneven wear of the tubes.

[@xfredoux]

@@purgasound Thank you very helpfull! Keep up the good work

[@dmcalister4505]

🤘🏼🎸🎶🎼🎵

[@zbaby82]

Don't mix power tubes people.