Cool ...


I was doing Engineering Production support on the
Panavia Nose mounted RADAR for the Tornado Aircraft
on the LRU 2 GMR (Ground Mapping RADAR) transmitter
back in it's early production run at TI -

- this unit's electronics for the power supply (-30,000
some odd volts for the *large* TWT amplifier's cathode
supply) which was bathed in Silicone Oil.

One of the test sets (for that *large* TWT) had an
access cover comprised of a 1" thick clear Plexiglass
cover over what was called the 'floating deck' board
(holding the grid control circuitry - this was a
grided TWT!) WHICH sat at that -30,000 some odd volt
potential ... this poor little board contained the
usual 5V TTL logic (popular at the time!) plus some
other odds and ends such as BITE (Built In Test
Equipment) circuits and the grid supply and control
circuity - oh, and the filament supply (after all,
this was a vacuum tube!).

Every so often if the techs didn't process the oil
(it had a propensity for absorbing atmospheric
moisture as the test set was not sealed!) an arc
would occur and take out several components.

One particular part was a 2 Watt carbon comp resistor
(don't now remember it's purpose) whose only remains
would be to bent leads (no body) aching into the board!
The sound when this occured was a muffled WHUMP! from
within the oil - and not much of a flash ...

"RF" Jim

    "Our ability to manufacture fraud has exceeded
     our  ability to detect it."

     - Al Pacino as Viktor Taransky in the movie 'Simone'



----- Original Message -----
From: "Brendan Moran" <bmoran@MILLENNIUM.CA>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, August 23, 2002 5:48 PM
Subject: Re: [EE]: The joys of electronics


> > Yup.
>
> Well, then, here's my experience on the subject:  First there was the
> sroting it with the metal nose of a mechanical pencil, which produced a
> moderate snap, as I'm sure you can imagine.
>
> Then, for some reason, I got the bright idea of trying shorting it with
the
> pencil lead, expecting nothing to happen due to the higher resistance in
the
> carbon of the pencil lead.  Well, instead, it superheated, I guess,
because
> it went off like a fuse, and gave a bit of a flash, and quite a pop.
>
> Good luck,
>
> --Brendan
>

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