"robb" wrote in message
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"Arfa Daily" wrote in message
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"robb" wrote in message
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I changed the CRT HV anode wire on TEK o'scope by ...
- removing the silicon glued cover/cap
- desolder old anode lead
- clean silicon
- solder new anode lead
- re-silicon the lead cover/cap

An AM radio nearby can give a good indication of corona
discharge. You get a
sort of a 'whining' noise. Breathing on the area with a good
"HAAAAA" will
also show up any tendency for corona, which takes place more
readily when
the air surrounding any potential discharge site, is made
moist.

Hello Arfa,

Thanks for reply.

Breathing with a HAAAAA ? is this going to be one of those the
HAAHAHA, the jokes on me kinda of suggestions ? where my ears
buzz, i see flashes of light and my eyebrow twitches for the rest
of the day.

Sounds suspiciously like one of those suggestions the Senior
engineers give to the new rookies to amuse themselves and the
other senior engineers.


No, it's quite genuine. You need to "HAAAA" like a giant sigh, rather than
blow like putting out a candle. This shifts a large volume of slow-moving
and moist air into the area. Any spikes on the soldering or poor insulation
on the HV, will discharge much more readily into moist air, than dry air. It
represents no danger to you, as nothing is going to jump that distance,
unless your 'scope tube has a PDA with about a 100kV on it ...



With the AM
radio on, wave a screwdriver around the area. Again, this will
provoke any
potential sites, and you should hear it.


as long as it does not provoke a zap on me then i will give it a
try.

The metal shaft of a screwdriver with a plastic handle, held in your hand,
will draw a good arc from a high voltage supply, without you feeling a
thing. In the good old days of valve (tube) only TV sets, it was a standard
test to pull an arc from the top caps of the boost rectifier and HOP valves.
Also, from the cap of a DY87 or the wires of an EY86 HV rectifier valve. You
couldn't do it in later sets, because of those new-fangled transistor
things, that would just expire if did anything like that within about 2
yards of them ! Anyway, the point is that if there is anywhere that has a
predisposition to corona discharge, a metal screwdriver blade waved in the
vicinity, will likely help it along. I'm not talking a big long spark
jumping out at you, just some ozone, or maybe a discharge that you can hear.


Trust me ! No dangerous suggestions from this quarter, ever ...


Thanks for the help Arfa,
robb



Arfa