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 Post subject: Fender Twin Reverb II
PostPosted: Sat Sep 29, 2012 9:10 am 
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I picked up the TRII a couple years ago and I finally have to replace my power tubes (a bandmate knocked it over while moving it and a couple shattered). As far as I know, there was no bias adjustment knob installed, there were sovtek 6L6's in there and I'd really like to upgrade the power tubes to JJ's, should I have any problems doing this? What would you reccomend?

Thanks in advance.


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sat Sep 29, 2012 10:17 am 
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Welcome, to the Jungle! (err... Board).

The Twin Reverb II seems to have a balance or hum pot and NO bias pot in the bias power supply. To be sure that you are running your new 6L6GC in the proper range, you'll need to have someone read the idle bias current and anode plate voltages.

Sorry.

http://www.webphix.com/schematic%20heav ... rev_II.pdf


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sat Sep 29, 2012 12:03 pm 
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so essentially I'll just have to take a stab at buying the tubes, then take measurements and hope they match up?


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sat Sep 29, 2012 5:44 pm 
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If that is the case you prolly should buy a matched quad of 6L6GC from a reputable dealer.

Remember, it's the idle wattage of each that is important. So, you'll nned to know the four anode plate voltages, as well as the idle cathode current. You'll be testing the amp "hot." So be careful! There is 400-500VDC under the hood.

Keep spekaers plugged in. Zero volume(s). Nothing connected to the input.

Good luck!


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sun Sep 30, 2012 2:19 am 
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jqmcandrew wrote:
I picked up the TRII a couple years ago and I finally have to replace my power tubes (a bandmate knocked it over while moving it and a couple shattered). As far as I know, there was no bias adjustment knob installed, there were sovtek 6L6's in there and I'd really like to upgrade the power tubes to JJ's, should I have any problems doing this? What would you reccomend?

Thanks in advance.


Bias adjustment is a must .

Not adjustment pot ? A tech could adjust bias with some resistor or installing bias pot.

But one thing is sure you can't install or find tubes without checking bias. Unless you are not worry about a poor sound or shorten tube's life.


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sun Sep 30, 2012 5:24 am 
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Bias adjustment is a must.

Absolutely. Or jqmcandrew, you'll will soon be back posting "What Happened?"

For the first amp, I'd find a good tech. He can also go over the filter caps and clean pots, sockets, and other connection points. If you decide later on to do some simple maintenace (and yes, output tube bias does drift with use) --- there a several Bias Adapters that can be bought and use with or without a DVM. I recommend a simple, but quality DVM, if you decide to do some mainentance on the amp.

Remember HIGH DC Voltage! You must respect it.


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 Post subject: Re: Fender Twin Reverb II
PostPosted: Sun Sep 30, 2012 10:59 am 
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BMW2002Ti wrote:
Bias adjustment is a must.

Absolutely. Or jqmcandrew, you'll will soon be back posting "What Happened?"

For the first amp, I'd find a good tech. He can also go over the filter caps and clean pots, sockets, and other connection points. If you decide later on to do some simple maintenace (and yes, output tube bias does drift with use) --- there a several Bias Adapters that can be bought and use with or without a DVM. I recommend a simple, but quality DVM, if you decide to do some mainentance on the amp.

Remember HIGH DC Voltage! You must respect it.


ABSO-TIVELY POSI-LUTELY!

+1000!

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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