James,

Great story!  And what fun!!

Did you discover (the hard way of course) that CRTs can have a residual charge after you discharge them by jumper wire? 

My company has a product that still uses b/w CRTs. We custom modify them so have to take them apart. When reassembling we re-ground the anode terminal to the ground band (which is making the electrical connection to the conductive outer coating of the glass envelope.

I don't have a scientific explanation as to why there can be a charge left.   You'd think the arc created when you initially discharged the tube would dissipate the energy. 

This is a perfect question for my former physics professor and renowned tin whiskers expert Henning Leidecker at NASA Goddard SFC so I'm cc'ing him :-))

Bob 

Sent from my iPhone

On Aug 19, 2013, at 11:19 AM, James Head <[log in to unmask]> wrote:

> When I used to work for Toshiba at the TV plant in Plymouth we were meant to break the tube necks before disposing of CRTs but we thought it was more fun to put them in the crusher unbroken and watch the old crusher shudder.  We once had a high-end special 44 inch tube.  We wheeled it out and very carefully lifted it up to place it gently face down in the crusher on its own, pushed the green button and hurried away.  There was a low thumping bang and the whole cage around the crusher rattled.  Crushing flat panels was not as exciting.
> 
> We used two large screw drivers to discharge the tube before working on a set.  Holding both screw drivers like sheers so they touched each other, we touched one screw driver on the ground side of the tube and wriggled the other under the anode cap.  I had a few 35 kV shocks though when I forgot to only hold the screwdriver by the handle (doh!). Fortunately I remembered to hold them correctly the one time when I tried to discharge a tube where the TV was still switched on - although we used 1:1 isolation transformers I suspect that it still could have been very painful.
> 
> James
> 
> James Head BEng CID+ MIIE MIET
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