[R-390] 6080 in place of 6802 - RMS ???

Tue, 8 Jan 2002 17:09:56 -0800 (PST)

Two 6080 tubes with series fillament would require 12.6v at 2.5A. If they were connected to a 25v
source with a single diode in series, then they would receive every posative (or negative as the
cas may be) half of the AC wave form. That is 25v for half the time or 12.5v Average

To obtain the RMS voltage one multiplies the Peak Voltage by 0.707 to arrive at the RMS voltage.

When talking about the AC voltages out of a transformer we ARE talking about the RMS voltages! NOT
the Peak Voltages. So ther is no RMS conversion necessary.

Rule of thumb is, if you apply the voltage for half the cycle, then you get half the current over
a full cycle (AVERAGE). So a pair of 6080's wired in series with a single diode, work on a 25v AC
supply and draw 2.5A for half a cycle or 1.25 amps AVERAGE over a full cycle, the R-390 (non-A)
25v heater circuit can take the extra 0.6A current.

Rodney
VK2KTZ

--- "Barry L. Ornitz" <[email protected]> wrote:
> Rodney Bunt <[email protected]> wrote:
> > 6080's can be used in place of 6082's in the R-390 
> > (NON A), if you series the filament for both tubes....
> > OR you could put a single Diode in series with the 
> > filaments if you have no aversion to "sand state" devices 
> > in your R-390 (NON A).
> 
> The 6080's filament is rated for 6.3 volts at 2.5 amps 
> while the 6082 filament is rated at 26.5 volts at 0.6 
> amps.  Two 6080 tubes with the filaments connected in 
> series would require 12.6 volts to run the filaments - not 
> 24 to 28.
> 
> Adding a single diode in series with the filaments will not 
> do the trick either.  For the umpteenth time, the RMS 
> voltage of half-wave rectified AC is 0.707 times the RMS of 
> the original waveform.  The misconception that adding a 
> diode in series will allow a 6 volt tube to run on 12 volts 
> appeared in several early tomes on the R-390 receivers and 
> sadly it still persists today.  
> 
> In the case Rodney suggests, the 6080 tubes would have over 
> 9.3 volts RMS on the filament of each tube leading to very 
> short life.
> 
>            Dr. Barry L. Ornitz     WA4VZQ     [email protected]
> 
> 

__________________________________________________
Do You Yahoo!?
Send FREE video emails in Yahoo! Mail!
http://promo.yahoo.com/videomail/