[Milsurplus] - SRR-11/12/13

[John Hutchins]

Kenneth -
Looked over the schematic - PDF file, for my SRR-13A , interesting the 
MOD for the ballast resistor is not shown on my version,  But I see 
where it could be implemented.  I have change 1 version in the PDF file.

Interesting that you brought up adding the screen dropping resistor 
modification, do you recall if the mod was done on the tube board or in 
a different location.  Do you know if there was modification, change 
order order?

Thanks
Hutch


On 1/27/2016 6:32 PM, Kenneth G. Gordon wrote:
> On 27 Jan 2016 at 13:57, w8au at sssnet.com wrote:
>
>> The RBA/B/C series remained in the fleet through the 1960's and even later
>> for auxiliary type ships.  This was, in part, because of the high-maintenance
>> required for the "replacement" SRR-11/12/13 types. (modular pencil tube
>> versions)
> One of the biggest problems with the SRR-11/12/13 series was that the
> designers set all the pentodes and tetrodes so that the screen voltages were
> identical to the plate voltages.
>
> The receivers ran incredibly hot with this setup.
>
> Back in the 1970s, I worked with a researcher who used a bunch of the
> SRR-11s running 24/7.
>
> I added a properly bypassed 56 K resistor in the screen voltage feed of each
> pentode and tetrode, which dropped the heat produced a lot, and they ran
> without problems from then on.  The reduced screen voltage did not seem to
> impair the receivers in any way.
>
> I got so I liked them...except for those damned pot-metal cranks on the
> band-switch mechanism which were always breaking.
>
> As long as one kept the receiver on one band, they didn't matter.
>
> Someone on Josh Rovero's page designed a cheap and effective fix for
> those things, though.
>
> BTW, the filament voltage regulator that RCA came up with to replace the
> ballast tube was sheer genius: a pair of back-to-back zeners and two
> resistors. Snazzy! :-)
>
> http://www.w7ekb.com/glowbugs/Military/SRR_Radios/Ballast%20Tube%20
> Replacement_files/Ballast%20Tube%20Replacement.htm
>
> Ken W7EKB
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