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Post subject: BIASING a Hot Rod Deluxe Question
Posted: Thu Jan 11, 2018 4:15 pm
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Aspiring Musician
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Where do you set the volume and tone controls when doing a BIAS adjustment on a Hot Rod Deluxe? I have done this years ago but forgot the particulars on that one question. I just watched some video's on the subject, and have a good idea how to do the rest of the job.

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Post subject: Re: BIASING a Hot Rod Deluxe Question
Posted: Thu Jan 11, 2018 4:31 pm
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No need to adjust vol and tone.
Bias must be done at 0 signal, no sound , nothing at the input.

By the book, volumes should be at 0.

But I never see any difference if volume is set at low / normal volume. It could be another story with a noisy 500 watts amp with volume at 10 :lol:


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Post subject: Re: BIASING a Hot Rod Deluxe Question
Posted: Thu Jan 11, 2018 4:45 pm
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Location: Province de Québec, Canada
HRD schematic show a B+ of 431 volts
6L6GC bias test point show 68 mv for both tubes

AB class amp work fine at 70 % tubes dissipation
Bias should be set close to 97 mv as show by Weber bias calculator .

Many Fender amps sound very good with colder bias , you must do your own test.
68mv look cold to me

http://www.tedweber.com/webervst/tubes1/calcbias.htm

You need to read B+ when adjusting bias. colder bias = higher B+
Hot bias= lower B+
Danger, lethal voltage Don't do this if you are not qualified

At 97 mv , B+ may go down to 410 volts ? And need new calculation


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Post subject: Re: BIASING a Hot Rod Deluxe Question
Posted: Thu Jan 11, 2018 5:00 pm
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Aspiring Musician
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Joined: Tue Nov 27, 2012 9:07 pm
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Thanks all for the good replies. I just called Eurotubes and they hipped me to the whole process. Once I was reminded of it I remembered but it is always good to check up on it before attempting to do so. I like the amp set for the cleanest headroom, so I will start at 72 MV which is where I usually set it before. I think the amp tech I just had it to, set it at 90+MV. I am changing the tubes myself as I think the ones in it are worn out.

Volumes to zero. And off we go into tonal bliss (I hope)

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