HV tracking across flexible PCB strips

[Jules Richardson]

On 05/11/2015 11:22 AM, tony duell wrote:
> [...]
>
>> However, there's a flexible plastic strip running between the CRT face and
>> the chassis which carries three lines (it's a storage tube rather than a
>> conventional CRT) and I'm still getting periodic arcing across these lines
>> which of course upsets the display's operation. As far as I can tell,
>> there's no 'sandwich' (and hence glue) involved - it's just a single
>> plastic strip with conductive traces drawn onto it.
>
> What does this strip connect to? Is it part of the CRT (or connected to the CRT), does
> it connect to a coil around the CRT, or what?

The CRT end is soldered to three terminals which protrude from the front of 
the CRT - one is presumably the normal anode connection, one related to the 
storage mesh which I gather that such tubes have, and I'm not sure about 
the third (but possibly to do with erase functionality? I've not found an 
explanation of how that typically works)

> I am wondering if there is something else leaking or flashing over which is causing
> excessive voltage to appear here.

Hmm, yes it could be that the HV is just too high and so it arcs over 
periodically (and by "periodically", it actually spends more time arcing 
than not) - although there's no obvious sign (change in brightness etc.) in 
terms of the displayed image immediately prior to it flashing over.

cheers

Jules