Discussion in 'Amplitude Modulation' started by KA4KOE, Jun 7, 2017.
Update, Friday evening.
They're wired backwards
Bob Henry quote worth remembering vis-a-vis 833 tubes:
I just love those 833A's ... "They're Glass Soldiers on the front line - poised and ready for service!"
833A's...more like a skinned rabbit.
But prettier than a bunch of bully-tube bomb 6146's.
You couldn't tell looking at mine, too much nicotine!
The Operator I got it from smoked like a train.
Well, you gotta' love any glass tube with a 350W. plate....
Notice that RCA mounted them upside down. Just as they did 849s, 204As and 851s. In fact, the old RCA transmitting tube manuals said they were supposed to mount that way.
For all the types named, or just the 833A ?
Had to be something about the tube's construction, because the tube manual wouldn't address practical mounting considerations. Wonder if you ever heard why?
Physical orientation can be important because of the innards. Many of the 807 type tubes, various manufacturers, suffered inter-electrode shorts when the tube was operated horizontally. The fortified 807W and military 5933 were recommended for such applications.
Yep, the 250-Watt base triodes like those mentioned even had the printing on the bases (there were two) oriented to show filament & grid on top.
The rectifiers, like the 869B were fil down.
I just love old tube lore....
But I have seen plenty of vintage photos of late 20s and early 30s transmitters that had them mounted base-down with the plate on top. I have often wondered if like Paul said there was something about the tube's construction that they recommended mounting them plate-down, and that operating them plate-up could somehow shorten tube life.
Those tubes, also the 833-A, can be safely operated in a sideways position provided the filament/plate structure is oriented in a vertical plane so that filament sag doesn't cause a filament to grid short. I always store transmitting tubes for any length of time vertically, since filament sag could occur even with a cold tube stored horizontally for an extended period.