BZZZZZT!!
I'll be waiting for your results on this one of course.
Wonder how many of the ones I have may be like that...?!
I ordered a pack of six, only about US$10 from local agent, as I have a feeling they will be useful for minimising signal noise as well. Will probably just chop up the BNC ends of one and splice it directly into the GND connection, and leave it inside the TV. Like this:
https://www.aliexpress.com/item/1005003772673736.html?spm=a2g0o.placeorder.0.0.ba49321eXLixwF&mp=1Even so, I think the hot chassis issue in TVs with SMPS (switch mode power supplies) is rare.
When looking at this TVs innards, at first I thought I must be crazy because the SMPS ground is shared with the main ground. Not by accident either, the PCB is printed that way. I was like "that is an SMPS - so why not HOT/COLD sides?". I scratched my head looking hard for an optocoupler, which normally sits across the HOT/COLD sides and shuts down power if things go wild, but there isn't one. I know that older TVs had HOT chassis but thought that went out with SMPSs.
Anyway, I eventually googled "hot chassis tv" it and found, on some 15-20 year old forums, that some early UK TVs (like National) with SMPS still had shared grounds until around 1980.
I don't have a schematic so have been working this all out by looking over the PCB
However, it has also been an opportunity go go over all the parts and testing where I can, redoing a lot of cold solder joins (power transistors literally loose in the pads). Surprising all the parts come out pretty good, even the old capacitors (they all test OK on the ESR meter). The Horizontal output transistor still works but is a bit suspect (relatively low ohms from collector to emitter), so I ordered a few of those too.