[Amps] Al-811 Troubleshooting

[Harold B. Mandel]

Dear Chris,

                The tube that's smokey is indicative of a vacuum leak.
The silvery deposit inside tubes is called "getter."  This deposit
attracts
stray oxygen molecules inside the vacuum tube. It "gets" the o2 to stick
to
its surface.

                 When there's a vacuum leak too much oxygen renders the
getter
into an oxide, hence the smokey, filmy appearance.

                  Chances are the seal around one of the leads became
leaky
because too much amperage made the lead hot. It expanded, then cooled and
contracted and left the glass expanded, such expansion and slower
contraction
yielding a vacuum leak.

                   My thought would be to examine the leads to all the
tubes to 
see if there was some component that changed value drastically, allowing
an increase of amperage in the tube lead.

                   Just swapping tubes may very well yield a similar
failure, and
that would be money down the drain and a waste of a precious commodity.

Hal Mandel
KA1XO/4