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6v pilot lamp

Trying to locate replacement bulbs for an old Wards / Airline transistor radio, they are 6.3V but only 20mA rated. Higher rated current lamps are out there, but in this design they dim the bulb when you tune a station, so looks like they must be that rating, which also saves battery power.

I thought an 1175 lamp would do but the current is wrong. It has to be a T5 screw type socket. Could not locate a bulb number for it...any ideas?

This is a pic.

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The front bulb is what came out of the radio 6.3v 20mA. The back one is a type 47, 6-8v 100mA way to big.

Reply to
UFO
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Closest thing I could find.

Lamp # 342 6V AC/6V DC 0.2W 0.04A T1 3/4 blub

from mcmaster.com/products/miniature-screw-base-light-bulbs/voltage~6v-ac/

Reply to
jim whitby

I replaced two of those fm stereo tuning lamps with two red leds. Still working after 20 years.........

Reply to
Sjouke Burry

Might be time to consider replacing the bulb with an LED and series current limiting resistor. The mechanical part - mounting the LED - might be a little challenging, but determining the resistor size is straight forward. If you're not sure of that, we can help you here.

Ed

Reply to
ehsjr

Been hearing that a lot for responses. Since the LED needs I guess 1.5V to be on, and can burn out with too much voltage, it did not seem to be a suitable option.

Reply to
UFO

That is why series resistors are always used. R = (Vin - Vled) / Iled

Arie

Reply to
Arie de Muijnck

Used to be a common part for analog meter illumination, so keep looking. Was once a radio shack number.

RL

Reply to
legg

Yes, Radio shack # 272-1140

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No longer availabe.

Reply to
UFO

Here's a diagram:

+6V ---resistor---LED---ground

Assuming a red LED you need roughly 1.5 volts applied to it. That means the resistor has to drop about 4.5 volts. We want the current to be 20 mA or less, so we'll choose 10 mA. The formula to determine the resistance is R=E/I where E is the voltage to be dropped and I is the current through the LED. So R = 4.5/.010 That equals 450 ohms, and the closest standard value is 470 ohms, which will work just fine. A 1/8 watt resistor is the smallest trough hole size and may be easier to fit in than a 1/4 watt. It depends on what you have on hand that will physically fit - the resistor will use only about .05 watt

The current through the LED does not have to be exact - anything from say 2ma (often much lower, depending on the LED) to 20mA will light it up nicely. If you want to use a white LED you can. A white LED needs roughly 3.2 volts so the resistor value changes to roughly 280 ohms, which means using a 270 or 330 ohm standard size. I'd use 330.

Ed

Reply to
ehsjr

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