21-04-2015, 04:11 PM
(17-04-2015, 08:44 PM)Yorkie Wrote: When you say 'the burnt cap' do bear in mind that if it's the mains input filter, if it's across the mains, it must be a class X one, or if its from line and/or neutral it must be Class Y. If you don't have the correct cap, you can remove the filter cap completely - it has no bearing on the performance of the set. The other cap that must be changed is the audio coupling cap to the grid of the output valve. (It would help if you mentioned the model number).
Every success with the restoration!
I've had a heck of a day! Ever seen The Incredible Hulk seventies TV series with Bill Bixby? For example, the pilot episode when he's changing his tyre, bangs his head in the middle of a storm and then the clothes start to rip and he turns green?
Basically, the output transformer on the Ultra ACDC set is held into place by screws and nuts so small, it's a nightmare to fit them back. I was at it for well over an hour, clueless as to how to get my hand in the gap so as to somehow hold the microscopic nut one side of the chassis while trying to get the screw to thread into it from the other side. No room for my hands. I think it was the part where the miniscule nut dropped into the speaker diaphragm that nearly drove me up the wall. Horrendous! I also remain clueless as to why the designers used such small bolts when there is ample room to place a proper bolt and create access to it!!
Guess how it resolved? I had to use superglue to glue the miniature nut to the end of a cocktail stick and gently try and hold it steady and ready to take the screw at the other side as it was turned. Meantime the force of the speaker magnet was pulling the screwdriver and clamping it. Yes, I did try to magnetise the screwdriver bolts but that didn't work at all as the bolts were immune. I
The rest of today's work went well. I enclose a pic of the new capacitor that goes across the output transformer quite neatly. They are film caps so what I did was clamp the wires with needle nosed pliers to sink the heat. I replaced both speaker wires and am happy I managed to solder decent joints.
Just one thing has had me worried now. When I tested continuity across the 0.01 mFD cap across the O.T., I was actually getting an Ohms reading. Also, a crackle from the speaker. I figured I must have burned out the capacitor so I shunted a new one across the connection without soldering and tested from the top. It still crackled and showed Ohms but not when disconnected. So, it must be something to do with the windings and magnetism.
