Quote:
Originally Posted by radio nut
thank you! I really do not like posting new questions about the same set over and over, makes me feel like like a forum hog!.
tell you what though, this set has been a real teacher since with help from this forum i have had to figure out a multitude of issues!
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Radio nut,
If you had added this symptom to one of your previous posts, that might have informed the rest of the forum what general vintage set you were working on and what you had done previously.
As for Phil's tube substitution suggestion, yes, that is the thing most books suggest because it is the easiest thing to do. With that said, I've found that it usually is not the problem
if one has done the standard visual inspection of an improperly working set.
This would include visually inspecting the horizontal output
under reduced lighting for either a pink glow on the plates, or a purple glow shining out from inside the plates. If so, replace the tube.
If the problem seen was pink plates, immediately check the difference in the grid voltage and cathode voltage to determine why the old tube overheated from pulling too much current or you will fry the new one in short order.
(Tubes with a purple glow may be used as long as they work properly without causing a problem, when confirmed by substitution. Sometimes, if you catch the pink plate issue
quickly enough and the cause is a fixable under the chassis component, the overheating tube may be salvaged, too.)
It is very rare to find Barkhousen caused by a horizontal output tube that is not showing these symptoms.
The pink plate problem can happen to any tube, and should be the first thing you do at your first power up of the recapped set! It is as basic as smelling for overheated parts. The most common in 40's & 50's tubes suspected of having this problem, in order of probability, are Rectifier, Damper, Horizontal Output, and Audio Output.
James