[R-390] Maintenance: mains voltage

[Charles A Taylor]

Crew,

I was on this reflector back in the early 90s, and had a loooong debate with
Gerald Johnson K0CQ about running an R-390A at less than 110 VAC
mains voltage.

I postulated running one at as low as 85 VAC, since I found that my own
Motorola would operate down that low.

He pointed out "thorium stripping" of the 26Z5 heaters and of the other
tube cathodes as a reason why this should not be done..

I have part of the debate still in my e-mail archives.

I believe that K0CQ acquiesced on running an R-390A at 100 VAC:
it would not be deleterious to the tube heaters.

Having settled that, I have operated my own set at 100 VAC, set via
a Variac.

I do NOT hit the set with a full 100 VAC at turn-on, but "ramp up" the
mains voltage over a period of about 60 seconds.

I acquired this set in 1984, and only last week replaced 1 of the two
26Z5s.

Unless you are down to the point of changing the air in your tires
and ACTUALLY cleaning out your attic, I would suggest not fretting
over the condition of the tubes.

Leave 'em alone, sez Ah. Jest mah too sints.

Charles

  Charles A Taylor, WD4INP
Greenville, North Carolina