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Post subject: Blackface Bassman Mod
Posted: Sun Jan 20, 2013 4:45 pm
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Hobbyist
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Joined: Fri Dec 23, 2011 11:24 am
Posts: 36
Hello again.

Is it possible to revert the blackface bassman back to the 6g6b?

Thanks


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Post subject: Re: Blackface Bassman Mod
Posted: Sun Jan 20, 2013 5:51 pm
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Professional Musician
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Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Yeah Rem, it's doable. But I would advise against the project. It would be quite an undertaking!!! And this is from a guy that stripped a 165 and reverted it to the 864 Bassman circuit. The main reason I got into it, was because the amp had previous bogus mods( someone tried to turn it into a Marshall. Don't think I'd try the project again!!! On the other-hand, you will certainly get a hands-on education, on how the amp works!!! Art

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Post subject: Re: Blackface Bassman Mod
Posted: Mon Jan 21, 2013 8:13 am
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Rock Star
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Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Yeah, I agree. The 6G6-B run 5881. This would mean changes to the PS rail and to the bias circuit of your BF Bassman, as the idle bias of the 5881 is below the 6L6GC.

The 6G6-B runs a 12AX7 (7025) in the PI, whereas the BF uses a 12AT7. So, this setup would need to change. Pretty big difference in idle bias between the two tube types.

Trannies seem to be all different.

And the gain stage (esp input) is run much "cooler" with the brownface amp (plave volts and idle bias).

Not to say this can't be done. BUT, if you should decide that you don't like the tone --- going back to BF standards will not be an easy thing. Of course, if you happen to have TWO Bassman BF amps.... :D


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

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


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Post subject: Re: Blackface Bassman Mod
Posted: Mon Jan 21, 2013 6:46 pm
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Joined: Fri Dec 23, 2011 11:24 am
Posts: 36
Thanks Guys, I was just wondering because I have a line on a 64'Bandmaster or a later bassman. I think I'll pick up the bandmaster and post pics along with the 69' pro reverb! :D


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