[R-390] 6082's and regulators

Thu, 02 Jan 2003 16:05:45 -0500

Hello All,

I've always found the R-390 non-A / 6082 regulator topic to be very 
interesting.   Some have installed MOSFET pass elements to replace the 
6082's, saving filament heat production.  Some have advocated moving a solid 
state regulator outboard to remove even more heat.   Others have tossed the 
solid state idea overboard.   Subbing the easier to find 6080 for the 6082 
has been discussed, complete with schemes to reduce heater voltage to 6.3v 
to operate 6080.  Attendant has been a free-for-all in the spirit of the  
BallasTube  thread.

A few have run the R-390A on completely regulated B+ (from an external 
supply) and report a "different feel" when tuning.   Maybe the "different 
feel" was due to a different AGC effect with regulated B+ not varying with 
AGC-induced power supply loading changes.  Maybe it was a different soreness 
in the wrist caused by tuning drag variation with different heating of those 
gummed-up geartrain lubricants.

I wonder if anyone has found any real measurable differences when operating 
an R-390A from a regulated B+ supply.

Drew

>Subject: RE: [R-390] 6082 tubes...
>Date: Thu, 2 Jan 2003 10:24:06 -0800
>From: "David Wise" <[email protected]>
>To: <[email protected]>
>
>In the R-390, they took the brute-force approach and
>regulated all B+.  During the Cost Reduction project,
>they found that the only really sensitive spots are
>the conversion oscillator screen grids.  In the R-390A,
>that's all that is regulated.  It's feasible to regulate
>this small load current with a VR tube.  With proper
>selection of circuit constants, this was found to be
>Good Enough.  They didn't even have to regulate the BFO
>screen.

<snip>

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