While I ponder the K networks and search for a tube socket, I'm moving onto the chassis underside. One electrolytic and a bunch of power resistors were replaced at some point.
One corner is finished so far. I've been using over spec resistors e.g. 2W for 1W and 3W for 2W.
I found one cap held in place by this nifty strap and was able to reuse it.
Very handy

Anyone know where I can get more ?