1. Dave, I definitely have a A146C. Look at the
circular hole. The marking on the backboard which says "A.C. Mains Receiver Type
A146C". The presence of PEN 45s and a UU6
valve. And the aforementioned two-core
mains plug sans earth.
I am not sure what you mean by "negative pin", as the circuit is A.C. it has a live wire which alternates charge, and a neutral wire. I assume you mean neutral?
2. Music-Centre/Steve, unusual as in bad? Don't worry that plug has been completely disconnected (mains wire attached for now), so as I never forget the dodgy wiring and try to plug it in.
3. Trevor, plug gone. The lead for the plug is PVC (everything else in the set is crumbling rubber) so it doesn't inherently NEED replacing. However, I suspect it to be a replacement piece already and it has barely any reach once fed through the set, so I plan to replace it with a new mains lead regardless.
The grommets will be replaced. Luckily, it seems to me that Murphy were relatively forward thinking with the 146C and no wires appear to actually go inside components. It is simply solder galore at different contact points. Also re:heat shrink wrapping, I believe I see some over some random points of the rubber wiring. I think this was probably a quick fix repair job in the past. I hope they didn't do any damage.
Thank you for your advice on multimeters.
4. Dave again, I have already started ID'ing components. I have given the set a quick clean to remove dust etc, and am using micro-porous medical tape to write small labels to put beside components. And over wires so I can trace what goes to where.
I will definitely look in to that biography! As someone with two literature degrees it will be good to read some non-fiction for once. Thank you.