[R-390] 6802 - and heat dissipation...+ standby

Mon, 7 Jan 2002 17:16:06 -0800 (PST)

Quite right, the HT is 185v, that is a lot of watts.... My understanding of "not using standby" is
the "poisoning" of the cathode, with filament current and no HT to "pull away" the electrons.

Note also how bright the "regulator" tubes glow when in standby, NOT GOOD !

The Hallicrafters SX-101A has the VFO tube fillament "ON" AND a "heater resistor" under the
circuit at all time even when the "power" switch is in the OFF position, they use a series
resistor in the filament to drop the heater current.

Is there a message for us, in this circuit design ????

Rodney
VK2KTZ

--- Bill Smith <[email protected]> wrote:
> Isn't the B+ in the R390 (non-a) 180 volts?   That means the tubes are
> working even harder.  350 - 180 = 170 volts.   170 X 0.3A = 51 watts!
> 
> That would take a very big heat sink, with fan.
> 
> BTW, for the millionth time, what is the story on the R390 (non-a) standby
> mode?  I haven't found any reason not to use that switch position.  Manual
> says don't leave it in for extended periods, but wonder if that is to avoid
> a poor practice of never turning the receiver off, and using standby as the
> on-off switch.
> 
> 73 de Bill, AB6MT
> [email protected]
> 
> 
> ----- Original Message -----
> From: "Rodney Bunt" <[email protected]>
> To: "Barry Hauser" <[email protected]>; "Richard Loken"
> <[email protected]>
> Cc: <[email protected]>; "blw" <[email protected]>;
> <[email protected]>
> Sent: Monday, January 07, 2002 4:08 PM
> Subject: Re: [R-390] 6802 - and heat dissipation...
> 
> 
> > The reason that the 6082's are HOT is that they are dropping the input
> voltage to 285v x the
> > current consumed by the R-390.
> >
> > Therefore power dissipated is (325 - 285) * .3A = 12Watts.
> >
> > This amount of heat would have to be dissipated in the "solid state
> regulator" anyway.
> >
> > I agree that the heat from 4 filaments would not be introduced into the
> receiver with a solid
> > state regulator.
> >
> > Remember that when the R-390 is in "standby" there is no current being
> drawn from the HT, so the
> > input voltage would rise to approx 360v+, that is 75v across the
> "collector - emitter" a big ask
> > for a Transistor, then again Power MOSFET could be used ....
> >
> > PS: Just think of the ZENER chain to get 285v for the "series regulator"
> !!! Then again you could
> > use tubes for that!
> >
> > Rodney Bunt
> > VK2KTZ
> >
> >
> > --- Barry Hauser <[email protected]> wrote:
> > > Richard wrote:
> > > > 6082's on the other hand...  I would not mind finding at least two of
> > > those
> > > > under a table some place.  It would be worth while to design a solid
> state
> > > > regulator for the R390 and put those hot and uncommon 6082's on a
> shelf.
> > >
> > > Check out Issue #52 of the Hollow State Newsletter -- reversable SS mod
> for
> > > 6082's in the non-A.
> > >
> > > Barry
> > >
> > > _______________________________________________
> > > R-390 mailing list
> > > [email protected]
> > > http://mailman.qth.net/mailman/listinfo/r-390
> >
> >
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> 
> 

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