Moving on a little from the frightening Y Lighting Adaptors, I used to have
a friend, presumably deceased now, back in the 1980's who had an homemade
contraption that used to rejuvenate TV tubes.
It was an OXO tin with a lightbulb inside plus other bits of electronics.
He used to connect a wire from the tin box to the back of the TV tube and
plug it into the mains. When the light glowed, he used to disconnect it, put
the TV back together and hey presto, one rejuvenated TV.
Now that was scary.
IIRC, this was done by overrunning the cathode heater for a short time.
Such a box would have been easy to make for the sets with 300mA series
heater chains in all their valves (valve part numbers starting with a 'P').
A 75W bulb would draw about 300mA, so connecting one in series with the
heater would run it normally. To overrun it, he probably used a 100W or
150W bulb instead.
That's not the way they worked. These 'crt reactivators' were commonly
made and used 20 to 30 years ago - I made and used several of them
myself in those days (and they could even be bought from spares'
suppliers). Essentially they worked by causing a heavy current to flow
between the cathode and the control grid of the crt. The heater was
'overrun' during the process, but the cleansing of the cathode - which
was responsible for the low-emission problem - was achieved by applying
a burst of high positive bias to the grid, while tying the cathode to
close to ground level.
That reminds me of the story about the atom who ran into an old atom
friend one day.
'Dear oh dear', he said to his friend, 'you're looking a bit fed up -
what on earth is wrong?'
'I've lost one of my electrons', said the friend plaintively.
'Are you sure?, said the first atom.
'Yes', said the friend, 'I'm positive'.
Ah well, I thought it was funny!
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