Joerg wrote:

joseph2k wrote:

Joerg wrote:


wrote:


and here we have a fine group i shall dub "the mu men" or "the
mu-see-ums" ;-))

solid, easy to get along with and sensible, no foolishness with p-layer
punch thru or bonding failures!

and tubes may actually be repaired too, nothing like those flimsy
silicon flakes!

:-))


Tubes are for real men. When they fail, they often do so in a rather
spectacular manner. Molten glass splattering about and all that.



And just what tubes were those? Of the about about 1000 failed tubes
that i have seen well over 95% were just filament / heater failures; and
not one broken envelope except for two mechanical shock victims.


PL509. Those are European color TV tubes used to drive the flyback
transformer. Similar to the 6KD6, probably. Just taller. There used to
be an odd rule for ham operator that had the highest license class in
Germany. This rule didn't limit max RF out but it placed a cap of 150W
on plate or collector dissipation as per data sheet. The PL509 was rated
30W so you were allowed to have up to five in there. Of course, everyone
knew that 30W was conservative and they were rated for continuous duty.
In SSB you could easily peak to 80W or more. How much more? That was the
white knuckle question. So, in the heat of the game there was the
occasional tube melt-down. Plates creaking, getting red, then bright
red, followed by orange, a wee spot of whitish glow ... KAPOOF!

I have seen PL509 tubes where the glass barely held on but was deformed,
basically sucked snugly onto the plate. They looked like a dog's chew toy.

OK, but even the text of post shows that that the tubes were being
intentionally operated well beyond their ratings. My dad talked about
pushing 6L6s like that, but never seemed to have a meltdown.
--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.Â*Â*
--Schiller