Bias a Fender HRDX

[SchecMan]

I'm about to pull the stock speaker out of my Fender HRDX and replace with a Jensen C12N. My question is should I bias the tubes after the replacement?

Thanks

[marvar]

Re: Bias a Fender HRDX

you do not need to rebias your amp after a speaker replacement.
as a side note- be sure you get a speaker with the correct impedance-not sure what your amp calls for though. 8ohms I suppose, but I don't use Fenders, so I'm not sure.

[SchecMan]

Re: Bias a Fender HRDX

I read that you should pull the power tubes before changing speakers. I guess this is done to keep the tubes from being accidently broken. I guess my question is should the tubes be rebiased if they have been removed and then put back in? Yes, mavar, you are right the speaker is 8 ohms.

[kmcguitars]

Re: Bias a Fender HRDX

Your gonna have to remove the whole chassis to change the speaker in a HRD. ( Most certainly 8 ohms) So while ya got her open might as well check the bias once you get it back together. It's pretty simple to do in a HRD if you have a DMM and some aligator clips. Need more help? Google J.Holton's
Unofficial Hot Rod Deluxe site.

[Gearjoneser]

Re: Bias a Fender HRDX

You don't need to touch the bias, if you're just pulling out tubes or changing speakers. It's a good idea to put power tubes back in the same way they were, although I'm not sure THAT'S even a big deal.

Do Hot Rod Devilles even have a bias pot? For some reason, I thought they were fixed bias.

[kmcguitars]

Re: Bias a Fender HRDX

Do Hot Rod Devilles even have a bias pot? For some reason, I thought they were fixed bias.

YUP! HRD and Deville's Have a Bias trim pot, And a very covenant Bias access point. Set Your meter to DCV, Use a alligator clip to put the + probe of your meter on the bias point, Ground the negative to the chassis.TAKE PRECAUTIONS NOT TO ELECTROCUTE YOUR SELF!!! Remember your reading two tubes so 68mV is a good reference point.
http://studentweb.eku.edu/justin_holton/bias.html