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Hot Rod Deluxe "Mod"

11/30/2004 11:04 AM
Al Lang
Hot Rod Deluxe "Mod"
Hello, A band mate has a Fender, single 12", Hot rod Deluxe, it's new. The problem is it's too loud for laid back giging. I was thinking of changing the 6L6s to 6V6s to get less Volume and earlier breakup. Does this mod sound worth the time...? Do I have to lower the B+ trail along with biasing the 6V6's, anything else? What B+ am I looking for at the first filter stage? Al
11/30/2004 6:35 PM
Don Symes

The HRDeluxe shows a B+ of 430V, compared to the AB763 BFDeluxe's 410V. With a high-quality pair of tubes, I think you'll (probably) be OK - gotta rebias, though.  
Crank the bias pot all the way negative before you power up with the 6V6s, and gradually raise the voltage 'til you get where you want - and a 1-Ohm Rk is right there (R166) for the pair.  
Hope I'm not wrong.
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12/2/2004 2:13 AM
Steve L.

I'd be really hesitant to put 6v6's on that much B+. Even that 410v rating is well out of the suggested range. Blackfaces run hot notoriously, and some tubes just don't work with that much overage. Putting even more strain on the tubes just sounds like asking for trouble.
12/2/2004 11:51 AM
Al Lang

What method should I use to lower the B+ to around 390v? Al
12/13/2004 12:57 PM
This amp doesn't have a center tap so the zener method won't work. What I would do is put a resistor value of maybe 47 to 150 ohms in series with will be able to still ajust the bias by reading across just the 1 ohm R66. This will reduce the effective plate voltage the output tubes see. Also the Electro Harmonix 6v6 don't seem to mind high plate voltage as much.
12/13/2004 3:50 PM
Bruce /Mission Amps

"This amp doesn't have a center tap so the zener method won't work."
Doesn't matter... you just use the zener in the grounded lead of the FWB.  
Or you can split the B+ lead that goes to the center tap of the OT and use the zener there.  
As long as the diode's cathode is always pointing back to ground through the FWB, it will drop it's rated voltage.  
Or don't do anything and use JJ6V6s which I have run at 22-24ma and 460vdc for hours and hours and hours!!  
12/13/2004 5:50 PM
My bad. Have not tried the JJ6V6's yet. I guess you like them Bruce? I've been using EH's with good results, but in older amps I've had to mod them somewhat to have them run the EH's cool enough.  
Gonna have to order a matched quad tommorrow and check them out.
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