Marconiphone T89DA

[ppppenguin]

The question of isolating transformer versus RCD is not a simple one. I know there is an excellent summary by Mark Henessey somewhere here on GVR. Generally, unless I'm using testgear with a set I'll use an RCD. The lamp limiter is irrelevant once the set has started to work. You won't hurt the big capacitors even if you short circuit them though the spark and crack may be disconcerting. An insulated probe with a resistor will do the job more gently. Value very uncritical. 100R, 1K, 10K, whatever.

I also made the point about switching off verss isolating. Never, ever trust the switch on the set. I learned that lesson the hard way many years ago. When I was a teenager I was fixing a neighbour's TV. Checked that chassis was connected to neutral by using a neon screwdriver. Turned off set, touched chassis, got belt. Live side of mains switch was stuck in the on position. On my own bench I trust that the sockets have their switches in the live side. I still prefer to see a clear gap by pulling out the plug.

Just to show that experienced folk make mistakes I gave myself a belt off a charged smoothing capacitor quite recently. The set had been off for a few minutes, amply long enough (so I thought) for leakage and any odd paths through the circuitry to discharge it. I was wrong. It was only a small belt but I should have discharged it regardless.