#1
Hey,

I want to swap out my power tubes but I need to know what's the maximum power they can run on.

Also if I get a bias probe and I just read the settings and make sure P is about 50-70% of the maximum power it's all good right? U and I are the things measured with the bias probe right?
#2
It depends on the amp and what the plate voltage is on that amp.
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#3
Generally speaking, I'd say 60 to 70% for class AB.
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Yamaha SBG500
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#4
Quote by Robbgnarly
It depends on the amp and what the plate voltage is on that amp.


It is a bugera v22, where can I read the plate voltage?
#5
Pin 3 is the plate.


Edit. Hang on, aren't V22's EL84? pin 7
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Mar 19, 2014,
#6
^ yep, EL84s.
That's the second time you make the same mistake TS, check that out next time.
Name's Luca.

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Clue: amplifiers amplify so don't turn it on if you need quiet.
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#7
Quote by Cathbard
Pin 3 is the plate.


Edit. Hang on, aren't V22's EL84? pin 7

Yeah, sorry. So I need to attach my multimeter to pin 7 of the power tube and the chassis of the board (something metal on the chassis of the circuit board)?

Is there some kind of table of what plate voltage would give what maximum power of the tube?
#8
Theoretically more voltage = more power, though there are a shit ton of other variables you have to keep track of, and you wouldn't wanna raise the bias voltage too much not to risk ****in' the tubes up after three months.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#9
Quote by Spambot_2
Theoretically more voltage = more power, though there are a shit ton of other variables you have to keep track of, and you wouldn't wanna raise the bias voltage too much not to risk ****in' the tubes up after three months.

Shouldn't I bias it with P=U*I? So voltage *current. Than you know how much warmth is produced in the tube per second? If I get a U*I which gives an optimal operating power, then I'm set right?
#10
Yeah, you should set it to an "optimal" operating power, not "to get the maximum power of the tube" as you wrote in the other post.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.
#11
Measure the voltage between pin 7 and ground. Multiply that by the plate current you read on the probe. That result is the figure you are looking for. Most probes will have a test point for plate voltage as well.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#12
Quote by Cathbard
Measure the voltage between pin 7 and ground. Multiply that by the plate current you read on the probe. That result is the figure you are looking for. Most probes will have a test point for plate voltage as well.

It's really that easy? ****.... why did it take me so long to realize.

Only question is.. I can just put the amp on with just 1 power tube running right? Because I need to know the plate voltage in pin 7 (which is the most at the right, correct?)?
#13
Yeah, you can pull a tube to measure it. Doesn't your probe have a plate voltage probe point? It would be pretty remiss not to have one.
Looking at the top of the socket it counts counterclockwise from the gap.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#14
Quote by Cathbard
Yeah, you can pull a tube to measure it. Doesn't your probe have a plate voltage probe point? It would be pretty remiss not to have one.
Looking at the top of the socket it counts counterclockwise from the gap.

I still have to get a bias probe, hard to get in the Netherlands.