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Post subject: EC Tremolux Tube change and re-biasing
Posted: Sat Jan 24, 2015 8:12 am
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I just purchased a EC Tremolux to go with my EC Twinolux and was thinking of changing some tubes. I was going to pull the GT6V6-R (4) tubes out and replace them with GT6V6-S (10) and put a Electro-Harmonix 12AY7 or a JJ5751 in V1
I see the Bias Pot ( the blue wheel ) but can anyone tell me where is the Bias point is for adjusting the Bias on the EC Tremolux and what is the factory default is?
Thanks
Leo


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sat Jan 24, 2015 5:07 pm
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You should do bias for the ( new ) tubes need not for Fender factory requirement witch is for the tubes Fender use .


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sat Jan 24, 2015 11:46 pm
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stratele52 wrote:
You should do bias for the ( new ) tubes need not for Fender factory requirement witch is for the tubes Fender use .


Yep, and I would be surprised if the bias from the factory was even set optimally for the tubes supplied, Fender amps are often biased cold from the factory and then completely opposite to this at the other end of the spectrum we see the Blues Junior has since it's introduction in the 90's been biased way hot out of spec, from the factory, something like 150% dissipation at idle.

To the OP, before changing the power tubes it would be worth making sure they are actually biased correctly, often that can improve the tone of an amp significantly. You don't seem to know how to check the bias, if you don't know anything about electricity and the potential to kill lurking in a tube amp, just take it to a decent tech.


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 2:56 am
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No457 Snowy wrote:
stratele52 wrote:
You should do bias for the ( new ) tubes need not for Fender factory requirement witch is for the tubes Fender use .


Yep, and I would be surprised if the bias from the factory was even set optimally for the tubes supplied, Fender amps are often biased cold from the factory and then completely opposite to this at the other end of the spectrum we see the Blues Junior has since it's introduction in the 90's been biased way hot out of spec, from the factory, something like 150% dissipation at idle.

To the OP, before changing the power tubes it would be worth making sure they are actually biased correctly, often that can improve the tone of an amp significantly. You don't seem to know how to check the bias, if you don't know anything about electricity and the potential to kill lurking in a tube amp, just take it to a decent tech.



+1


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 6:17 am
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I know how to bias amps, I have biased my Blues Deluxe Reissue and Hot Rod Deluxe but those have printed on the the board the bias set point and I know what Fender's recommended Bias is. There is no bias set point marked on the board for this amp and I have no clue what the recommended starting Bias is. Because the amp uses 6V6 power tubes I was thinking somewhere in the area of 20mA per tube.


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 6:33 am
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If you know how to bias;

1- Why are you looking for Fender bias setting ? You must look for the bias tubes ( you put in ) need not what Fender printed on the circuit .

2- You know that you need to read plate voltage before to know if tubes need 20 ma

That is what I call "know how to bias "

Use this
http://www.webervst.com/tubes1/calcbias.htm


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 7:11 am
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Maybe I did not have my coffee yet and am a little bit touchy but I thought the purpose of forums like these were to ask and share information, to help others with their questions not to be a snarky and condescending. If I needed that I could find much better places to go get abused.
Thanks for nothing.................


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 7:17 am
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Yesterday ,we give you all answer .

You say you come to the forum to get information.
If you want good information you must accept to tell you your mistakes.
I can not be honest with you without mentioning it


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 8:59 am
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Sorry leo, maybe Mr Shimm will know and post bias chk pts, he did for my Supersonic 22. I went in and sure enough they were cold from factory. But then again i have ALWAYS turned the wheel and biased by ear, dont care what the critics say, sounds good, no Great!

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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 1:38 pm
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Hey leo, i couldn't find where tp are, but i did find this viewtopic.php?f=13&t=82792

I would just bias by ear and feel the chassis in case its getting too hot worked for all mine


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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 3:34 pm
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The schematic shows 370 VDC going to the OT, this is approximately the Plate voltage, but it's best to check to be sure. The schematic shows no test point to check the Plate current or Cathode current, but it does list a factory bias setting of 27 mA for Plate current.

Assuming 370 VDC for the Plates, and using 6V6, 14 watt tubes, the Plate current should be set to the range of 19 mA to 27 mA. Personally, I would go for the middle of that range, around 23 mA. Using bias probes to check Cathode current is close enough, and leaves a little room for raising the current.

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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 6:28 pm
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leodgr81 wrote:
Maybe I did not have my coffee yet and am a little bit touchy ....


I must be lacking in coffee myself as I agree with you. I thought this was a forum for musicians not some thinly descised car forum where the default reply is attack, belittle and generaly be obnoxious.

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Post subject: Re: EC Tremolux Tube change and re-biasing
Posted: Sun Jan 25, 2015 7:56 pm
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John Sims wrote:
leodgr81 wrote:
Maybe I did not have my coffee yet and am a little bit touchy ....


I must be lacking in coffee myself as I agree with you. I thought this was a forum for musicians not some thinly descised car forum where the default reply is attack, belittle and generaly be obnoxious.


When dealing with voltage and current that could potentially KILL you, it's best to be brutally honest and call it like it is. I Certainly didn't read any of what you've described into the advise given, but maybe it's because I DID have my cup of coffee.... :wink:
All kidding aside, stratele's intentions are always with concern for safety and making sure no one is harmed.....including the amp. Everyone else has offered sound advise and links to informative web sites.
Best of luck to Leo and yourself.

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