HV tracking across flexible PCB strips

Jules Richardson jules.richardson99 at gmail.com
Mon May 11 18:58:08 CDT 2015

On 05/11/2015 03:17 PM, tony duell wrote:
>> Hmm, while regular electrical tape is only rated for 600V, Scotch-brand
>> "splice tape" is rated for close to 22kV. Of course that's *through the
>> tape* though, so although it would insulate the conductors from the outside
>> world, it's not clear how effective it would be at insulating the two
>> conductors that are only a couple of mm apart; the tape doesn't really play
>> a part in that scenario, only the glue.
> Given that flashovers don't seem to do any damage, I would be inclinded to just
> try the tape first and see if it will stand up to the voltage. If it is only 3kV, I suspect
> it will. I would not start cutting the flexiprint unless you have to.

Well, the tape proved to be a no-go; it was still tracking along the glue. 
So, I bit the bullet and removed the flexible strip, replacing the three 
conductors with wires.

Thankfully the CRT didn't break, and it's cured all the arcing problems. 
However, whatever the connection point closest to the CRT front is for, 
there's essentially nothing to solder to; unlike the other two connections, 
it only protrudes from the glass by a fraction of a mm.

I'm really not happy with it as a "fix" because I doubt the joint has any 
mechanical strength worth speaking about, and it's likely only the tape 
which I then wrapped around everything which is holding things together 
(and of course over time the tape may stretch and the connection may fail).

I suppose that at least for the moment it'll do, and allow me to test out 
the XYZ inputs and perhaps think of a way of repairing the flexible strip 
(of course that solder problem will remain, but it would be much easier for 
tape to hold a big flat strip in place than it is for three round wires)



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