AU-D5 Power Meter Illumination - How to make side emitting LEDS

[skippy124]

Hi,

I recently repaired a AU-D5, and part of the repair included replacing the Power Meter lamps with LEDS. The Power meters are "side illuminated" via two 8V 150ma bulbs, and one fo these was out, it was the weekend, I wanted to get it finished and rather than wait until I could get hold of a couple of replacment bulbs I decided to convert to LEDs. In kow that side emitting LEDS are available, but I wanted to get this done straight away, so I did a mod on the LEDS I had to convert them to side emitting.

The power meters with one lamp out

A standard white T5 high brightness led

The LED with the top filed off

Next step is to get a small "box cutter", mark the centre of the led, and then rotate. The object is to gouge out a cone shaped hole in the LED, being careful not to slip

Keep "gouging" until you get a cone that is almost the diameter of the LED (adjust the angle of the cone as you go so that you don't go too deep and hit the LED die)

This is what a standard LED looks like on

and this is what the modded LED looks like on (it is had to get a true comparison as the camera adjusts to the light output from each LED)

And with a flash on so you can see the "illuminated cone"

I added a little bit of liquid paper the the surface of the cone and that improved the light output a little

Mounted in the light panel

A simple mod where the lamp wires connect to the 8V AC output on the PSU PCA (half wave rectified, smoothing cap and current limit resistor (one resistor in each LED lead pair)

And the final result

Pretty happy with the result, and I was able to get the amp repair finished without waiting for parts to arrive.

Cheers

John

 

[markn2wae]

Awesome!

******* awesome! :tresbon:

I have always wanted to make "side firing" LEDs that would work where standard lamps "use light from the side" to illuminate things.:yes:

If you needed light in only one direction, perhaps you could just grind a "flat" spot on one side of a fresh LED and do it at a 45 degree angle?:scratch2:

There is a tip, get an ultra violet led, grind or shape it to how you need and paint the surface with "glow in the dark" black light paints in the COLOR YOU NEED!:thmbsp:

I haven't tried this yet, but I think this is how they make "white" LEDS.

They are just ultra violet emitters, and the manufacture puts a dye inside that's florescent "white" when powered up (kind of like a "solid state" florescent standard tube).

Cool stuff!

Mark T.

 

[Alienz]

This should be a sticky! :tresbon:

 

[LBPete]

Or you could buy these and plug and play.

- Pete

 

[skippy124]

Or you could buy these and plug and play.

- Pete

Nice link, they would do the job very well, but as I said I was after something that didn't have to be ordered in as I wanted to get the amp finished as soon as possible.

 

[ghazzer]

Nice work John, and great documentation. Wonder if you could just use a drill bit, twirling it with your fingers. Might not be the same angle, but certainly easier.

.

 

[LBPete]

There is no simple easy answer to your question. LEDs are diodes. They are not resistive like light bulbs. An LED will fail in short order if you wire it into a circuit without a current limiting resistor. The value of that resistor is dependent on the voltage which is 8V as you stated, and the current draw and voltage requirement of the specific LED(s). Here's a link to one of many LED resistance calculators available on the web. The resistor doesn't need to be exact. A higher value will decrease the brightness of the LED. In most cases, a 1/4w resistor is fine.

The spec sheet for the LED will give you a brightness specification along with the other data you need for the calculator. As a rule, white and "warm white" LEDs are pretty bright. You may have to experiment a little to get the brightness you need to match the original bulb.

The "smoothing" cap he used is a nice touch but is probably not necessary. LEDs work fine with no noticeable dimming on the typical AC power supply used in most lighting circuits.

Hope this helps.

- Pete

 

[LBPete]

Another way to get a "side firing" LED is to bend the leads 90 degrees if you have enough room. It works for some of the G models that side light the acrylic dial lens. Because of the nature of the acrylic lens, the LED doesn't necessarily need to be placed in the original position but if you move it, you may need several to illuminate the lens evenly

- Pete

 

[LBPete]

AC or DC, it makes no difference. The resistance calculation is the same. Use a 1/4w resistor.

- Pete

 

[Josnor]

Hi, i know this is a old thread but i have the same amp with the same problem and i am unable to find a replacement bulb, can someone point me i the right direction of where to find the correct type of led that i will be able to install, and what wiring modifications i need to make, thanks