It's not a pull chain. It's just there to keep the HV box cover from getting lost.
What servicing has been done to the TV? It will need an overhaul to work properly. Replacing all the paper caps at the very least.
It will look something like this underneath the chassis. Those black plastic "bumble bee" caps need to go. The eletrolytics caps should be replaced too.
It's a solid design, but a whole lot of caps to replace.
