question about power tube bios

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question about power tube bios

Post by drsakky » Sat Jul 09, 2011 11:05 pm

This is probably a silly question, It looks pretty simple to bios the rm100 I saw a video on it on youtube.
What I want to know is when biosing the amp can you do it with the amp on just standby or do you have to plug into a speaker box and have the amp fully on ?
The video does not show this.

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Post by BigBrewtus » Sat Jul 09, 2011 11:27 pm

Yes your amp needs to be plugged into a cabinet and standby on play. Be sure your master is completely off.
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Post by GuitarGod87 » Sun Jul 10, 2011 12:51 pm

I made the mistake of not flicking the the standby switch to on the first time I tried to bias my head. I bought the amp used off of ebay and when I saw no voltage on my volt meter, I saw red thinking someone ripped me off a few hundred bux, lmao. But yea, both switches have to be on and make sure you have the head plugged into the cab.

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Post by drsakky » Mon Jul 11, 2011 4:15 am

Thanks for replies, I asked because on the video the guy hasnt got a speaker lead plugged in.

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RM100 Bias

Post by Exoticwood » Wed Jun 04, 2014 2:29 pm

what do you guys like to Bias your power tubes to, and why?
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Re: RM100 Bias

Post by webrthomson » Wed Jun 04, 2014 3:48 pm

Exoticwood wrote:what do you guys like to Bias your power tubes to, and why?
Hey - it depends on the type of tube in question (actually the tubes watts dissipation rating) and the plate voltage of the amp - for the technical stuff see the eurotubes generic bias link here: ... rshall.htm

Randall / egnaters suggested bias's are as follows (for the RM100/RM50/Mod100/Mod50):

6L6/5881 28mV to 35mV
EL34/6CA7 30mV to 38mV
E34Ls 35mV to 45mV
6550 35mV to 45mV
6V6 (JJ Only) 18mV to 22mV

(KT88's are bias'ed as 6550's)

From the RM100 manual here: ... manual.pdf

And the Mod50 manual here: ... (3-07).pdf

Hope that helps - any questions let us know

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