Tubes Asylum: RE: selecting out and testing 8417 by ivan_terrible Questions about tubes and gear that glows. FAQ

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Posted by ivan_terrible (P ) on December 14, 2018 at 06:26:56

In Reply to: RE: selecting out and testing 8417 posted by 6bq5 on December 12, 2018 at 14:18:41:

I took a little more time to select out the other pair after yesterday.

This shouldn't really happen, but there is nothing wrong with these.
After 2h they are dull red plating, both of them equally.
I check and they are at 42m/a quiescent.

That is 27W at 630V which is dead in the window for Ab1, and shows the 8417 is really struggling as a book 35W OPV.

The spread of such valves is such that they will glow in one place, not all over at the same time (unlike some of the best TV horizontal scans).
They must have been a right PIG to make.

I don't like to see that, so I selected a pair which are more in the 32-36m/a window, and as a result those don't glow.

The others go away until I have such time to rip the bias circuits to bits (in the MO200 which is coming), and do it all properly.

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