[Milsurplus] Smart People: Multi-Set Current Corn-fusion

[Bruce Gentry]

With low B+, the tubes may not be fully conducting, even if they are 
performing well enough to give reasonable results.   The main problem 
with low B+ will be much higher intermodulation distortion, poor AGC 
action, and higher audio distortion.  If screen dropping, cathode, and 
plate circuit resistors have risen in value, operation may also appear 
satisfactory  but current draw will be below expected levels.  As an 
aside, were your receivers built in Schenectady or Syracuse?

         Bruce Gentry, KA2IVY

On 12/3/17 9:09 AM, David Stinson wrote:
> Dear People Smarter Than Me:
>
> I'm confused.  Bumped-up the RAX "burn-in" to 100V
> B+, which is provided to all three receivers from
> the same buss, using a current-limited supply so
> if any of the old parts decides to "shuffle off
> this mortal coil," the supply will shut that down.
> Did some current measurements with all sets in the
> same operating mode:
>
> All sets connected and off:  13 mA, within 1 mA of
> expected.
> LF set playing alone: 30 mA (has fewer stages than
> the others).
> LoHF set playing alone: 41 mA.
> HiHF set playing alone: 46 mA (about 10% "hot,"
> will check).
> but:
> All three playing normally at once: 83 mA.
>
> Ummm... shouldn't that be like 117 mA?
>
> Anybody got an idea?
>
> 73 OM DE Dave AB5S
>
>
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