The Elmer's Shack
DIY Hams
Replacing burnt out incandescent meter lamps with LEDs
Here is a guide to replacing burnt out meter lamps in
ham rigs, CBs, SWR meters, and linear amplifiers meters.
1. Use “flat top” LEDs as seen in the picture.
“Flat tops” have a wide angle of light dispersion, upwards of 140-180 degrees. DO NOT use typical “rounded top” LEDs, as they have a low angle 15-45 degrees of light dispersion, which creates a spot or beam effect.
“Flat tops” have a wide angle of light dispersion, upwards of 140-180 degrees. DO NOT use typical “rounded top” LEDs, as they have a low angle 15-45 degrees of light dispersion, which creates a spot or beam effect.
2. Use LEDs with several thousand “mcd” in intensity. Many of these "flat top" LEDs are available on ebay and other sources, for very low cost.
3. What are the advantages of LEDs over incandescent bulbs? The LEDs will likely never burn out and will outlast the rig, or even outlast you. In some transceivers, they also do not dim when keying up.
Installing LED based on a 13.8 VDC source:
1. A 560 ohm drop resistor must be soldered to the anode (longer lead) of the LED, then solder the resistor to the positive lead of the voltage source. The 560 ohm resistor value is a generic value that should cover all the LED color ranges.
2. Connect the cathode (shorter lead), to the negative side of the voltage source (shrink tubing may be needed for both leads).
Installing LEDs based on voltage source other than 13.8 VDC:
If you have a voltage source other than 13.8 VDC, you can use this LED Calculator to calculate the resistor that is needed for your voltage source.
You will need the LED “Typical Forward Voltage” and “Typical Forward Current”.
For “Typical Forward Current”, you can just use 20mA.
For “Typical Forward Voltage”, it varies by LED color.
Basic values for these “Flat Top” LEDs are the flowing:
Some LED color forward voltages, may vary slightly from above, but are usually available from the vendor where you purchase them from.
Voltage source should be measured at the leads that connect to the LED.
Hints:
As mentioned above, a 560 ohm resistor is a common value and good generic value for 13.8 VDC source. If you do not have a 560 ohm, you can use higher values, like a 1K ohm, at a slightly reduced intensity. Don’t lose sleep trying to find a 560 ohm, if you do not have one. The reduced intensity might not be noticeable.
Many people love the different color LEDs, because they look cool on the meter.
Some SWR meters have very small lamps. The LEDs mentioned above are based on the very common 5mm LED. If you have a meter that has a very small lamp and a 5mm will not fit, you can get the same “flat top” in a 3mm size.
Vinnie Sallustio, N4NYY
3. What are the advantages of LEDs over incandescent bulbs? The LEDs will likely never burn out and will outlast the rig, or even outlast you. In some transceivers, they also do not dim when keying up.
Installing LED based on a 13.8 VDC source:
1. A 560 ohm drop resistor must be soldered to the anode (longer lead) of the LED, then solder the resistor to the positive lead of the voltage source. The 560 ohm resistor value is a generic value that should cover all the LED color ranges.
2. Connect the cathode (shorter lead), to the negative side of the voltage source (shrink tubing may be needed for both leads).
Installing LEDs based on voltage source other than 13.8 VDC:
If you have a voltage source other than 13.8 VDC, you can use this LED Calculator to calculate the resistor that is needed for your voltage source.
You will need the LED “Typical Forward Voltage” and “Typical Forward Current”.
For “Typical Forward Current”, you can just use 20mA.
For “Typical Forward Voltage”, it varies by LED color.
Basic values for these “Flat Top” LEDs are the flowing:
- Red, yellow, orange, amber = 3.0 VDC
- Blue, green, clear white, warm white = 3.4 VDC
- Pink, Purple = 3.2 VDC
Some LED color forward voltages, may vary slightly from above, but are usually available from the vendor where you purchase them from.
Voltage source should be measured at the leads that connect to the LED.
Hints:
As mentioned above, a 560 ohm resistor is a common value and good generic value for 13.8 VDC source. If you do not have a 560 ohm, you can use higher values, like a 1K ohm, at a slightly reduced intensity. Don’t lose sleep trying to find a 560 ohm, if you do not have one. The reduced intensity might not be noticeable.
Many people love the different color LEDs, because they look cool on the meter.
- Blue seems to be especially popular.
- Ice white seems to best bring out the colors of the meter.
- Do not use clear white. You will not like it.
- Warm white is best if you are a purist and use vintage rigs. Warm white LEDs are as close to replicating the “incandescent” color of typical light bulbs, as you can get. They also look much better in vintage equipment.
Some SWR meters have very small lamps. The LEDs mentioned above are based on the very common 5mm LED. If you have a meter that has a very small lamp and a 5mm will not fit, you can get the same “flat top” in a 3mm size.
Vinnie Sallustio, N4NYY