....briefly. Did I do something wrong? When I turn off the switch, and the pilot goes off, the radio continues playing strong for several seconds and then slowly fades away. I've never experienced this before.

http://www.nostalgiaair.org/Resources/377/M0017377.htm

As long as there is a minimum level of B+ voltage and cathode emission, the tubes will keep working. I suspect that many tube radios are like this, but we never notice because the on/off switch is on the volume control.---ie the radio is always shut off when it is not producing any sound.

It would be interesting to know what sets the time: B+ decrease (discharging of the filter caps), or emission decrease (cooling of the filament/cathode)

Philco intentionally did this on some clock- radios in the late 50s and early 60s . They marketed it as "lullaway". The fading out has to do with the filaments loosing power and the b- connection still seeing the input. Double check your work. Chances are you have a miswire or solder blob. Trace the power switch path to rectifier, rectifier out and switched filament path.

I don't know nothin' bout that, but I wouldn't count on getting the voltage readings as indicated in the schematic!

If the on-off switch is part of your volume control it shouldn't continue playing. The volume control will be at min when the radio is turned off. Maybe your volume control has a bad spot at the end?

Radios with a toggle on - off switch or part of the tone control may continue operating a couple seconds after turned off for reasons others mentioned.

The volume control is a separate pot. The second click of the on/off is the bass/tone position.

Entirely normal. The heaters are still hot, and there's still some B+ left in the power supply until the heaters cool and the B+ charge diminishes. It's the sign of a healthy power supply. You'd find the same in a radio with the switch on the volume control by pulling the plug with volume normal.

These days it's not unusual to have a handful of 330uF, 160 volt electrolytics handy. They're quite popular in switching power supplies and photoflashes, so there's lots of them around. Some of the ones from cheap disposable cameras have no markings on them at all, and they're easiy confused with 22uF 160V caps as they're about the same size.

If you recap a radio with those, it will play fine, but it will "run on" for a few seconds due to the excess capacitance.

The solution is to recap it with values more in line with the originals-- not more than 47uF per.

to test this theory leave your radio at half volume and unplug it from the wall

I was using my Bogen 30 watt public-address amplifier at a fairly low volume for speeches at a meeting. Someone knocked the plug out of the outlet, and the amplifier continued working during the 5 to 10 seconds it took to plug it back in. Push-pull amplifiers don't draw much current at the usual speech volume, I've checked with a kill-a-watt meter.
Don

The one 30 mfd is a 30, the one 16 mfd is a 22 and the other 16 is a 30 (slight error by me). I skipped the 25 mfd/25 volt. I'm doing it now. And I'll see what unplugging it does.

OK, I did that last 25 mfd. If I unplug the set, the audio stops immediately. If I turn off with the switch, it's still a slow fade away.

Wow, that's interesting! This radio uses a bridge type voltage doubler. Here's a "clarified" drawing of it:

I can't account for the behaviour you describe though. You don't have a ground wire attached, or used a 3-wire line cord with the ground to chassis by any chance, do you? No, on second thought that would probably blow a fuse. I dunno!
Do you get the same thing if you reverse the line plug?

edit, here's a thought: The antenna circuit is probably making use of the line to complete its circuit from antenna, throught antenna coil to chassis, then through the power supply to the line and to ground. When you yank the plug, the antenna circuit loses its path to ground and the signal greatly loses its strength, even though there is enough "residual power" from the caps to keep the radio going. Maybe?

This set is unique though, Although a doubler is used, the 150 Volt line is half wave, and the 265 Volt
is full wave.

If that's the case you likely have a wiring issue and the rectifier is still seeing line voltage, radio continues to play till the tube cathodes cool enough to stop conducting.... I'll bet there is a wire connected to the wrong lug on the switch, if you haven't changed anything it could be a factory flub...


Tom