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Old 25th Jun 2016, 15:30
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Loose rivets
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Join Date: Jun 2001
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The main, and almost all, dangerous stored voltages are in the tube. More precisely, between the outer conductive coating of the glass and a similar coating on the inner surface. The voltage on a colour TV are much greater than on the old black and white tubes - and they were capable of giving a good sting.

Colour EHT is much more dangerous, as even without the capacitance of the tube, the voltage, 30kv or so, will sustain while trying to make you jump about with your eyes crossed. Add to this the storage of the tube's capacitance and you'll find Darwin's law comes into play about the time you stick a screwdriver under the rubber connector to see what that's all about.

However, while the voltages on the tube's base are not to be sneezed at* it should be possible to tease at the little PCB and its components with a trusty knitting needle. A well-positioned mirror, or a semi-skilled friend, should be placed to monitor all progress. It might help if the friend was also a nurse skilled in resuscitation procedures.

One's trust in knitting needles should only extend to ones made of plastic.


*The C&G course on telly-mending repeatedly stressed the inadvisability of sneezing - either metaphorically or literally - upon all things electrical.


My lecturer at PYE Cambridge told me of a time he'd awoken in hospital to be told he'd had an electric shock. That didn't surprise him that much, but what did leave him aghast was his rubber heel marks tracking across his lab's ceiling. A mere 9kv, but EHT from a hard-wound transformer.
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