[R-390] Ballast Tubes - Resistor

[Bob Camp]

Hi,

Looks like anything between 47 and about 56 ohms will work just fine. 
Ten watts or larger should last forever.

I finally posted the whole mess to the correct mailing list a few 
minutes ago. I'm not sure what the Teletype guys made of a big long 
string of stuff about R-390 resistors. Gotta watch the keyboard a bit 
more closely in the future ....

	Take Care

		Bob Camp
		KB8TQ


On Jul 3, 2004, at 2:05 PM, Rbethman wrote:

> Group,
>
>    I've pulled the resistor in my R-390A.
>
>    It is a Sprague "KOOLOHM", 50 ohm 10W.
>
>    It goes between pins 2 and 7.
>
>    Mr. Camp - what say you?
>
> Bob - N0DGN
>
> David C. Hallam wrote:
>
>> According to my RCA Tube Manual a 6BA6 is rated 6.3 V at 300 mA, so 2 
>> tubes
>> in series 12.6 V at 600 mA.  Supply voltage is 25.2 V so you want to 
>> drop
>> 12.6 V with 600 mA of current
>>
>> 12.6/0.6 = 21 ohms
>>
>> 21x0.36 = 7.6 watts
>>
>> A resistor ( 21 ohms at 10 watts would seem right
>>
>> David C. Hallam
>> KC2JD
>>
>>
>> _______________________________________________
>> R-390 mailing list
>> R-390 at mailman.qth.net
>> http://mailman.qth.net/mailman/listinfo/r-390
>>
>>
>
> -- 
> <                      Bob Bethman - N0DGN
> +-------------------------------+----------------------------------+
> | N0DGN AMRadio Manassas, VA    |    REAL Tube Radio and AM        |
> +-------------------------------+----------------------------------+
> |       Manassas Radio - Home of Homemade Kielbasa & Pirogi        |
> +-------------------------------+----------------------------------+
> | Bob Bethman                \\\|///     " The absence of a danger |
> | rbethman(at)comcast.net   \\ ~ ~ //      signal does *NOT* mean  |
> |                           (/ @ @ /)      that everything is OK " |
> +-------------------------oOOo-(_)-oOOo----------------------------+
> |               <http://home.comcast.net/~rbethman>                |
> | 1 BC-610I w/BC-614I,1 T-213/GRC-26 w/BC614I 1 '51 Collins R-390A |
> | 1 '67 EAC R-390A, Heathkit DX-60, Apache, Mohawk, SX-101, HT-32A |
> +------------------------------------------------------------------+
> |           Amateur Astronomer - Celestron Nexstar 8               |
> |             12" f5 Dob coming soon!  Being built                 |
> |                  Meade ETX-60 (Got it back!)                     |
> |               38 Deg 46.8' N - 77 Deg 28.5' W                    |
> +------------------------------------------------------------------+
> |   Opinions expressed are that of my own and do not necessarily   |
> |         coincide with or represent those of ANYONE else          |
> +------------------------------------------------------------------+
>  ALL E-mail received and sent scanned by AVG & Norton Anti-Virus>
>
>
>
>