Fender Silverface Tube Bias 3 Steps Output Tube Match Tutorial

[@thesuncollective1475]

I used to rehearse at a youth club in Tottenham London with one of these..great amp..great warmth and clarity..Nice vid thx

[@ZacharyRyanMusic89]

im buying a 79 70 watt on friday. this was super helpful thanks for making these videos

[@LearnAudioEngineering]

Glad I could help, have fun!

[@taku319able]

great tutrial!

[@waynegram8907]

I still hear the 60hz hum even when you have adjusted the Bias trim pot and Hum balanced trim pot, any reasons why the 60hz hum is still there?

[@ryanreidy]

i had a single power tube break in my twin and I was fretting over having to buy a whole set. your manual excerpt said i *don't* need to buy a whole quad set?

[@thesongtowoody]

There is a pot accesible through a tiny hole on your chassis above the speakers if your looking at the unit from the backside with the back panel removed preferrably. it has a slotted screw pot. check this using small mirror and a flashlight. (this applies for my 73 twin reverb, it should apply to a 74.) This knob is NOT a "fine" bias, that is a mod that can be done as an addition to "stock" from fender. This knob (the first i was talking about) is to balance the 4 tubes as "one". So, the two left of each other to the two right of each other. Like a balanced scale of power. In a perfect world youd have a matched quad, if not two match pairs to use this "balance" pot.

[@velvetonecustomshop5026]

Hey.... 1974 Twin... no adjustments on the back panel besides the ground.... I also have 2 tubes (power) pulled... been this way for years, but I want to replace power tubes with 4 new ones... is this a fixed bias?

[@thesongtowoody]

There is a pot accesible through a tiny hole on your chassis above the speakers if your looking at the unit from the backside with the back panel removed preferrably. it has a slotted screw pot. check this using small mirror and a flashlight. (this applies for my 73 twin reverb, it should apply to a 74.) This knob is NOT a "fine" bias, that is a mod that can be done as an addition to "stock" from fender. This knob (the first i was talking about) is to balance the 4 tubes as "one". So, the two left of each other to the two right of each other. Like a balanced scale of power. In a perfect world youd have a matched quad, if not two match pairs to use this "balance" pot.

[@captainamerica9353]

Interesting, now could you show how to do this with an old Princeton or Princeton Reverb that doesn't have a bias adjustment?

[@shckltnebay]

They have a fixed bias but can be adjusted by replacing a resistor in bias supply

[@thesongtowoody]

anyone notice he uses two different pots to make adjustments? how can that make sense?

[@lehrgangswerk]

I have this amp for 36 years now. Only a few people know about the hidden push pull master volume knob. Try it !

[@LearnAudioEngineering]

I trying mine but it doesn't seem to have an effect :/ what am I missing?

[@lehrgangswerk]

@@LearnAudioEngineering did you pull the knob?

[@lehrgangswerk]

@@LearnAudioEngineering I can send you a photo.

[@shckltnebay]

That was on the Deluxe and the Princeton NOT the Pro

[@lehrgangswerk]

@@shckltnebay not right. I have it on my 70 pro reverb.