Hi, not sure if this is the right place to ask, but here goes.. I have an old 1960's radio that uses two 6 volt incandescent lamps for the dial. Would it be possible to substitute these for NE-2 neon bulbs? The side contact on the bulbs connect to the chassis of the radio which acts as earth.
Yes! However you would need to disconnect the 6 volt supply and then provide suitable dropper resistors from the HT for the neons.
I can't for the life of me understand why you should want to do this. The 6v bulbs are available and cheap enough.
--
Best Regards:
Baron.
I want long life bulbs in the radio as it's hard opening the radio to replace the bulbs. I could go with LED's if that's easier.
I forgot to mention that this is a transistor radio, the only high voltage is at the transformer. Perhaps LED's are the easy way. Some bright orange ones would do. What resistors would I need for them?
** Use 9 or 12 volt bulbs - you goose.
Last for a decade, or more.
NE-2s will never produce enough light.
...... Phil
I thought of that, however as the existing pilot lamps are hidden behind the dial and reflect off the clear faceplate, they aren't bright enough now, so 12 volt bulbs would be ineffective. I'm thinking of going with bright LED's and bringing them around the front of the dial for more light.
** LOL - wot a wacker.
** Vintage ones.
...... Phil
In which case I would definitely stay with the incandescent bulbs!
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Best Regards:
Baron.
Hi, The1930s. A bit of a problem here -- older transistor radios used the low voltage AC secondary for the lamps, not DC. That means you'll have to drive your LEDs with a series diode, too.
I'm assuming you've got a 6.3VAC secondary which is driving the lamps. Orange LEDs require around 2V forward voltage drop when on. If you add a 1N4001 diode in series, you might want to start with a
220 ohm, 1/4 watt resistor. The end product will be the resistor and the diode in series with the LED.Good luck Chris
The radio does work without the lamps. I think I will go with LED's. I've found a "sunset red" red LED at the Dick Smith Electronics web site, but I can't check the voltage because the site keeps crashing.
Especially since the bulbs are there to luminate the dial, and neon bulbs aren't likely to supply the same amount of light. Their place in things is usually indicators of voltage rather than to supply light.
Michael
I've been thinking about that, I will check the specs when the stupid site lets me. The LED is advertised as super bright, I don't won't a dim one, there's no point in that.
I have some 1N4002 and 1N4007 diodes. Would they work?
Yes. These diodes will all work for the low voltage of the 6V lamp socket. A 1N4002 blocks to 100V, a 1N4007 to 1000V. Save the 1N4007s for higher voltage if you've got both.
I should mention that some radios have the incandescent bulbs in series, which would mean a 12V secondary. Try pulling one bulb, and seeing if the other goes out. If so, you may have a 12VAC secondary.
As above, a 220 ohm, 1/4W resistor in series with the LED and the
1N400X diode should work fine if there's a 6VAC secondary. If it's a 12VAC secondary with the bulbs in series, then make sure to replace both incandescents with LEDs, or it won't work. Also be sure all the LEDs and diodes are lined up so the anodes are toward the more positive side, or it'll be a frustrating experience.When you're at the website, look for the "viewing angle" to see if the LED light is tightly focused. You probably want a wide angle LED here.
Good luck Chris
Not without some tinkering with circuitry. A 6 volt incandescent requires 6.3 volts nominal at something like 100-200 milliamps to light.
A NE2 or similar small neon requires about 60-80 volts or so to ionize the gas and then the current has to be limited to a few milliamps with a resistor.
You might substitute an LED with suitable dropping resistor and a rectifier since most OLD toob type radios used AC for the pilot lamps
- they even make replacement LED lamps with bayonet and screw bases with built in resistors - for DC.
If you are dead set on neon for esthetic reasons it can be done, but requires more arm waving and head scratching.
One thing - does the radio work without the lamp bulbs in place? Some of the old AC/DC radios put the lamps in series with the filament string of the tubes the lamps would initially come on very bright then quickly dim to normal as the tubes heated - without the lamps the radio wouldn't play at all or be very distorted and weak sounding.
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I' going to have to stay with the existing lamps. I inspecting the radio and there's no way the LED's will fit between the faceplate and the dial, without filing a hole in the faceplate, and I don't want to do that. Thanks for all your help.
You can simply run two LEDs back-to back. If you have enough voltage, you can run two strings of two diodes (4 total) back to back with a smaller resistor, and get more light for the same power. LEDs are current-sensitive devices - the resistor is there to limit the current, but the voltage dropped by the LED may vary a bit - ideally, you might want to measure the actual voltage dropped by the specific part in hand when adjusted to the correct specified current - use a potentiometer and a milliammeter, and start with a high resistance on the pot (too little current is fine, too much current is a one-time magic-smoke-releasing event. Then stuff in a resistor just a bit larger (for a safety factor) than the reading on the pot when you have the pot adjusted for the rated current. If you have 6 volts, you should certainly be able to run 2 red or yellow LEDs in series.
You might get a better color using a red and a yellow or green. Depends what color you want...
The ones I presently have in stock list a typical forward voltage at
20mA of 2V and 2.2V, with maximums of 2.5V and 2.6 V - so if you have 6.3V available, pick a resistor to drop ~2V at 20 mA and it should work to drive 2 in series. ie, 100 ohms, for that example. Your parts may vary - typical circuits are designed to underdrive the LEDs to keep them safe with part variations (ie, 270 ohms from 5 volts in series with a single LED.) 6.3VAC~-------- | \\ / \\ 100, 110, 120 Ohms (progressively dimmer and safer) / | ------- | | \\/ -- Back-to-back LEDs -- /\\ | | |------| (connection here keeps reverse voltage low) | | \\/ -- -- /\\ Back-to-back LEDs | | ------- | --- --- Cats, coffee, chocolate...vices to live by
Red LEDs require about 1.8 - 2.3 volts to light and most standard size - 20 milliamps so would require a dropping resistor to limit current, as well as rectifier - many leds only withstand a 5 volt reverse voltage before they self destruct.
But check the specs.
When they specify light intensity in millicandellas or mcd that is the light output in a specific area of the target - the beam width and intensity have to be considered. The light of an LED is directional - something to consider when replacing incandescent's with leds.
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Well - there's all kinds of leds today. I have a few in my MC tail lamp that are rated in lumens, dissipate a watt each, and have a 120 degree beam spread.
Overkill for a pilot lamp.
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