Magnavox Dial Lamp

4/28/2000 8:43:30 PMBrian

I'm working on a Magnavox am/fm table radio model #Fm017,
looks like from the late '50s. There is an #1847 lamp
in the set, but it glows dimly, suggesting it is the wrong
lamp. I tried a couple different lamps I had, but no
luck, still dim or dark...however, if the lamp is removed,
I lose audio, as it looks like the lamp is wired with one
leads to the rectified dc on the electro-cap and the other
side to one of 5 leads coming out of the audio out transformer
primary side. Also, there is a 12k 0hm-3watt resistor between the
2 leads of the lamp in the circuit. Short of getting the
schematic, any ideas out there? Otherwise, it plays great.
Never seen this type lamp circuit before, looks like original
wiring. (Could need a 3 volt lamp, which I don't have)

4/29/2000 1:35:54 AMNorm Leal

Hi Brian

The 1847 lamp is rated at 6.3 volts @ .15 amps. It seems like your lamp is wired in series with the B+ of the radio. A lamp rated at lower current would be brighter.

If the circuit is correct, over time tubes will draw less current making the light dimmer. Changing electrolytic filter caps may help. Voltage will be higher and with higher voltage tubes draw more current.

What rectifier do you have in this radio? If 35W4 tube the lamp should be wired differently but if it is a selenium rectifier Magnavox had to find a different way to get voltage for a lamp.

The schematic for your radio is in Sam's Photofact #943. You may be able to get this through your local library.

Norm

: I'm working on a Magnavox am/fm table radio model #Fm017,
: looks like from the late '50s. There is an #1847 lamp
: in the set, but it glows dimly, suggesting it is the wrong
: lamp. I tried a couple different lamps I had, but no
: luck, still dim or dark...however, if the lamp is removed,
: I lose audio, as it looks like the lamp is wired with one
: leads to the rectified dc on the electro-cap and the other
: side to one of 5 leads coming out of the audio out transformer
: primary side. Also, there is a 12k 0hm-3watt resistor between the
: 2 leads of the lamp in the circuit. Short of getting the
: schematic, any ideas out there? Otherwise, it plays great.
: Never seen this type lamp circuit before, looks like original
: wiring. (Could need a 3 volt lamp, which I don't have)

4/29/2000 1:47:46 PMBrian

: Hi Brian

: The 1847 lamp is rated at 6.3 volts @ .15 amps. It seems like your lamp is wired in series with the B+ of the radio. A lamp rated at lower current would be brighter.

: If the circuit is correct, over time tubes will draw less current making the light dimmer. Changing electrolytic filter caps may help. Voltage will be higher and with higher voltage tubes draw more current.

: What rectifier do you have in this radio? If 35W4 tube the lamp should be wired differently but if it is a selenium rectifier Magnavox had to find a different way to get voltage for a lamp.

: The schematic for your radio is in Sam's Photofact #943. You may be able to get this through your local library.

: Norm

: Thanks Norm,

The radio has a 'regular' diode for dc, and caps

are strong. I'll try to find a lower current bulb.

Didn't know you can get Sam's thru library, how

does that work?

4/29/2000 2:01:07 PMNorm Leal

Your library may not have Sam's Photofact but they can request it from a main library. When I request the information it usually takes a few days.

Norm
:
: : Hi Brian

: : The 1847 lamp is rated at 6.3 volts @ .15 amps. It seems like your lamp is wired in series with the B+ of the radio. A lamp rated at lower current would be brighter.

: : If the circuit is correct, over time tubes will draw less current making the light dimmer. Changing electrolytic filter caps may help. Voltage will be higher and with higher voltage tubes draw more current.

: : What rectifier do you have in this radio? If 35W4 tube the lamp should be wired differently but if it is a selenium rectifier Magnavox had to find a different way to get voltage for a lamp.

: : The schematic for your radio is in Sam's Photofact #943. You may be able to get this through your local library.

: : Norm

: :

: : Thanks Norm,

: The radio has a 'regular' diode for dc, and caps

: are strong. I'll try to find a lower current bulb.

: Didn't know you can get Sam's thru library, how

: does that work?