16-04-2015, 03:40 PM
(15-04-2015, 05:12 PM)Radio Fixer Wrote: You don't do it like me. I replace (actually re-stuff) all the wax caps and stuff the electros with new (forget all the reforming stuff just more work later) and change any across or down mains caps for X or Y. Then test all the valves and go to stores as needed. Get rid of all old rubber covered cable, and line cable, and look for dodgy (over heated resistors) and measure and change as needed. If its a set I'm going to keep I actually measure everyone even if it means disconnecting (most don't).I find the service manual help me a lot. I don't have the exact manual as it's not listed but I do have a very closely related model by Ultra of the same era and appearance. And I'm familiar with the All American Fives. I think I may start my way from the power supply and outwards as I try and fix up dodgy wires and semi melted wax caps.
Check the mains on off switch for low Ohms and insulation. Check all pots with an audio genie and a pair of headphones.
Then power it up, don't need the Variac.
Each to there own way of doing it. First thing when powered up is to measure HT (have a meter hanging on there from the moment I go "click") is to measure cathode volts, O/P valve is vital. And I have a plug in cheapo mains meter measuring current and watts, one eye on that. They may be cheapo but actually have DSP and measure RMS.
Gotta go: dinner bell Gary
These were pretty clever designs of the time. Live mains supply directed via rectifier valve to supply H.T. plus DC and then the non rectified live branching off to heat the heater valves filaments in series. Eliminates any need for a transformer,
The scale lamp layout always had me a bit confused as I think the design varied a bit. On my Ultra the scale lamp runs through neutral I think and many sets used a shunt resistor.
In the following pic you can see above a sooty brown cap that's even worse. I will definitely not be powering this up again till it's vastly safer.
