I did a repair event in North London this week, and we had two auto-changer record players from the 1950's come in, both single valve amplifier, and one of them used an EL84. (Actually, we had three, but we didn't get time to look at the last one.)
The owner had already done his research on the internet and found the likely problem was the electrolytic capacitor had dried out. It was a single can with 3 capacitors inside, and he had bought replacement capacitors. He had removed the old capacitor (together with half the nearby PCB tracks;-) but then got cold feet about going any further. I soldered in the new capacitors (had to be on flying leads and tie-wrapped to the output transformer). Initially, it didn't work, at which point I had to mentally trace out the circuit on the board (very simple). There was no heater voltage at the valve, and I then realised the old capacitor which had 3 earth tags on the case was actually relying on two of them being connected by the old capacitor case (or by a track which was now gone). Having fixed that, it all sprung into life. The look on the guy's face was one of unbeliveable surprise - he clearly had never expected the gramaphone was ever going to work again!
The other gramaphone was not so easily repaired, sadly. At some point it had been stored in the damp. Most of it was not damaged at all, but the shaded pole deck motor laminations had rusted so they were forced apart. Initially I thought that wouldn't matter, but I had to remove the motor because it was siezed. Thought this would be one of the bearings, but having removed them, it was actually the rotor was jammed in the stator laminations by the rust. It wouldn't budge. Ran out of time at that point. The single valve in this one was a PCL, i.e. a triode pentode dual-stage amp.
I was a bit surprised finding a P... value in a single valve appliance - they were 300mA heater valves designed to be used in TVs and other appliances with many valves, so the heaters all ran as a single 300mA series chain, direct from mains via a dropper resistor if they didn't all add up to mains voltage. Conversely, the E... valves such as the EL84 above (single pentode) run on a
6.3V heater supply, which was provided by the mains transformer.