Discussion in 'Amateur Radio Amplifiers' started by W8JX, May 15, 2015.
Pump is most important. A lot crap out around 28 or 29 inches of vacuum.
Well I guess it depends how hard you are pushing them. I don't normally get any glowing on SSB.
But if you run at full power on CW and are sending slowly (like I often do for DX on 160) it can mean a long over with long characters . . .
As Carl said, these valves are massively under-rated in these amps, so the anodes are bound to get pretty hot when used like that.
I guess it's also subjective - what you describe as a glow may be what I call red ! (and I've never seen them go orange)
The SB-1000 is a cost reduced AL-80A and was designed by Ameritron. Before that was the AL-80 and before that the L-75.
Can someone tell me what pulling a vacuum externally to a vaccum tube does. I'd really like to know. Never tried it, but I'm trying to figure how that helps.
If a vacuum tube has a leak that let air in, pulling an external vacuum may help evacuate the tube, but the leak remains. Kind of like pumping up a flat tire...might work for a short while, but if you didn't fix the leak, it will just go flat again.
Guess I'm not getting how it helps.
Come on Steve. Everyone knows the way to fix leaky valves is with Bar's Leaks....
That or two cups of oatmeal!
Yeah, I guess. Pretty temporary. A bit like touching up the X-rays because you can't afford the operation...
Pulling a vacuum and heating the envelope might fix a 6146 I have.
I'd love to hear how that helps.
It wouldn't, but it's nice to think it would. It developed a short between the control grid and the screen grid, causing the plate to overheat and the envelope to partially collapse. I caught it before it had a chance to collapse far enough to implode.
You have to seal the leak as soon as you remove the tube from the Vacuum chamber.
Hard As Nails nail polish works good, and it will dry as it gets sucked onto the leak, and seals it.
I use clear Hard-as-nails, Guess you could use colored to see where the leaks were easier. Not sure if the dye/color would cause Ark over, I have never use it. The Clear works fine.
Have Fun, Save Tubes.