On the ON indicator light lamp sockets for a lot of the equipment I am working on. They are rated at about 6.3v since they are connected to the heater voltages. I want to replace these lamps with LEDs. I calculated the resistor that I would need to reduce the voltage to about 3.5v for the led bulb was about 150 ohms. However after I connected the resistor and inserted the led in to socket I am reading 5v across the led terminals. I don't want to burn the led out, is there something that I missed?

 

The 6.3V filament voltage might be AC. But an LED uses DC. The max reverse voltage for most LEDs is only 5V but the peak of 6.3VAC is higher at 8.9V.

If you use a diode in series with the LED then it might be seen flickering at the mains frequency. If you use a full-wave bridge rectifier then its flickering is at double the mains frequency which might not be objectionable.

 

Is the 6.3 AC or DC? If AC use a diode in series [ 1N4002 etc ] anode to cathode, with 110 ohm resistor & LED, any order. You can also parallel LED with diode, anodes to cathodes, using 150 ohm resistor.

 

Yeah silly me it is AC. I try the diode approach out. Thanks for the tips.