Steve and the group
It was always said that a picture is worth 1 k words
richl
http://www.svetlana.com/docs/TechBulletins/technoteNo54.html
Steve Thompson wrote:
>
> I have a pair showing odd behaviour. I'm interested in your comments. These
> were bought at very modest price, reflecting their 87/8 date codes and
> untested state (all I could do was check heater continuity and electrode
> shorts - both were ok). I trust the source, who said they were pulled from
> working equipment. They sat for a long time while their project didn't
> happen, then I got a chance to test them in a friend's 6m PA. One was just
> fine, the other did nothing at all and showed an o/c heater when checked.
> They went back on the shelf for a year.
>
> Recently I wanted to find the good one, but hadn't marked which it was. The
> DVM said BOTH had good heaters! After much fiddling, I found that they were
> both intermittant - the 'right' way up, and a tap with a finger made both
> ok. Other positions and harder tapping would make them go open, one more
> readily than the other. Having got connection, I ran the heaters up very
> slowly, then at full voltage for 24 hours. Both had stabilised as good with
> normal handling. A few weeks on, and the worse one has gone open again.
>
> Some aspects of this are blindingly obvious, but I can't find a picture of a
> heater/cathode assembly anywhere to satisfy my curiosity and let me puzzle
> whether they might prove useable if they were settled in a stable
> environment. Maybe I'd need to build in a solenoid tapper as part of the
> turn-on sequence :-)
>
> Steve
>
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