View Full Version : neon stereo indicator bulb

05-30-2011, 07:23 PM
Anyone familiar with NE-2 Neon Bulb used for stereo indicator? I just want to find out the average hours (Lifespan) this bulb will last .....I have one in my Knight Tuner, and eithor flickers, or won't come on, on Strong Signal....Thanks for your help, as always

05-30-2011, 07:30 PM
Like this one? (

05-30-2011, 07:33 PM I have installed has about 1000 hours , since being replaced.....multiplex is fine, just the bulb......

05-30-2011, 07:42 PM
That link claims 25K rated hours.

05-30-2011, 07:46 PM
Hmmmmmm thanks, guess must be something the 50 year old tuner.....maybe time for alignment again, or a weak tube, or weak something.....I just spent over $1000 on the thing.....

05-30-2011, 08:42 PM
While your tuner may have some issues, it is not unusual for the elements in a neon lamp to degrade, raising the voltage needed to fire the lamp.

I then functions as a relaxation oscillator, causing the flickering that you see.

Depending on the lamp, it may need something over 65VDC to fire. You can measure the voltage to the lamp on both sides of the series resistor.

One odd thing about neon lamps...If they are flickering and you shine a bright light on them, they may stop flickering and stay on.

The lamp is the first thing I would check by measuring the voltage going to it when the tuner is tuned to a strong stereo station. If that is low then you will need some tuner repair.

05-31-2011, 07:05 AM
Thanks, I will check voltage first, and or replace the bulb...even when the bulb does not light, I still get stereo seperation....guess for a radio that is 50 years old, I can't complain....that stereo indicator never worked well since it built the tuner, otherwise it is a workhorse...just keeps on going

05-31-2011, 11:59 AM
check the resistor in the bulb circuit. If that drifts high in value, it will get less voltage than it ought to have.

05-31-2011, 01:28 PM
Thanks , I will just change resistor, and the bulb....and see if that takes care of the on going problem.....stay tuned folks

05-31-2011, 02:14 PM
It is possible that the driver circuitry for you neon lamp is just on the ragged edge of supplying enough voltage. You might be able to lower the value of the series resistor by a small amount and then the voltage after the lamp fires might be enough to keep the lamp lit. You would just be reducing the voltage drop across the resistor.

Of course this assumes that all is well with the tuner and the circuit driving the neon lamp.

06-02-2011, 02:26 PM
thanks.....I will try that and see what happens ....I appreciate your help

06-02-2011, 02:32 PM
Slightly off topic, but is there an easy way to replace neon lights with LEDs?

I mean, is there a simple resistor/diode circuit? With some specific values?

06-02-2011, 06:45 PM
I would be interested replacing the Neon with a LED as, if anyone has any comments, please do so....the Voltage on my Neon Bulb is 36 v

06-03-2011, 02:55 PM
Hey Guys.....I got lucky.....someone recently replaced the resistor in that circuit, so, just replaced the Neon Bulb....and when fired up, came on bright, and steady.....thanks for all your help.....:)

06-03-2011, 02:58 PM
That is great:thmbsp:...

It is always nice when a repair is simple.

And gear sounds better when all the lights work:D

06-03-2011, 06:49 PM
Yeah, for a 50 year old Am/Fm Stereo tuner (Knight Kit) it sure does sound is better than any newer tuner I have.....although not as much stereo seperation as the newer tuners...only 30db.....but, I can live with that, just as long as it sounds good, and all the lights/tuning eyes work....

06-03-2011, 07:59 PM
Slightly off topic, but is there an easy way to replace neon lights with LEDs?

I mean, is there a simple resistor/diode circuit? With some specific values?

As a first cut, assuming a 120VAC line application, I would go with a 12K 2W resistor and a reverse diode across the LED to protect against reverse breakdown. That yields about 14mA on peaks, which should give plenty of brightness for most jobs, but it's low enough to maximize LED life for the most common 20mA types. You could use a series protection diode instead, which cuts resistor power in half, but I wonder about reverse leakage in cheap power rectifiers hurting the LED.