Most lamps are wired in such a way that B+ current also flows through them. Your radio doesn't draw B+ current until tubes heat.
Radios are wired this way to save lamps. The response of a lamp filament is much different than a tube. If a lamp was wired directly in series with tube filaments it would burn out on radio turn on.
Norm
: Can anyone answer this question? I just replaced all of the capacitors in a 1941-era 5-tube Emerson AM radio. The set works fine with no hum across the band. My problem is, the panel bulb that is wired into the rectifier burns very dim at first when the set is energized. When the tubes warm up, the bulb brightens to normal bright intensity. Can anyone tell me why the bulb starts off dim? Is this abnormal? Does it point to any condition that I need to look at? Thanks if anyone can help.
I had never tried to run the 5 tube unit when I first got it, until I had replaced all of the capacitors and the 50L6 final (open filament), so I didn't know if I had done something out of the ordinary to cause it to behave this way.
Thanks very much for the help Norm;
Nelson
I should have mentioned this only happens on AC/DC radios. These are radios with tube filaments wired in series across the AC line.
Lamps won't act this way in a radio with a power transformer. Your Emerson probably has a power transformer. In this case the lamp will get voltage directly from a filament winding.
Norm
: Thank you Norm;
: I wasn't sure if it was normal or not. I have another 7 tube 2 band unit Emerson with two dial lamps; these lamps do not dim during unit warm-up, so I wasn't sure if something might be wrong with my 5 tube unit.
: I had never tried to run the 5 tube unit when I first got it, until I had replaced all of the capacitors and the 50L6 final (open filament), so I didn't know if I had done something out of the ordinary to cause it to behave this way.
: Thanks very much for the help Norm;
: Nelson