Suggest a Simple Circuit

[Yankee Dog]

I want to change one of my receivers over to led's. I have tested the look (with the blue white color that the white led's provide) and am good with it.

My issue is the power that supplies the old bulbs is 10 volts AC. I do not need DC to run the led's. I just need to get the 10 volt ac supply down to 3 volts to supply 8 led's I have 2 wires from the transformer that go to the circuit board strip that holds the lights.

I thought about a LM317 and a standard regulated circuit to get the 3 volts, but that would mean another little circuit board with a rectifier to change that to DC. I don't need the dc and would rather not get into that.

Just want to cut the power down at the wires that connect to the circuit board strip to 3 volts. My next thought was a resistor that would handle the 8 leds. I was thinking a wirewound in about a 3 watt range at 300 ohms.

Will the wire wound work with such a low amp draw? The leds are 20-25ma each. Any other simple ways to cut the ac from 10 volt to 3 volt? I suppose I could use individual resistors at each led bulb, but that would be my last resort. Not sure on how that would look and the circuit board itself is pretty narrow. I'm looking to reduce the power at the 2 wires that are soldered on the board. Thanks YD

[Stevesmullen]

I dont know if you need it but there is a program on the web that can calculate all of your LEDs and give you exactly what resistors you will need to make them work properly.
Im not sure what the web site is but if you need it and cant find it shoot me a email and I can find out.

[avionic]

LED voltage dropping resistor calc.
http://led.linear1.org/1led.wiz

[EchoWars]

...My issue is the power that supplies the old bulbs is 10 volts AC. I do not need DC to run the led's. I just need to get the 10 volt ac supply down to 3 volts to supply 8 led's I have 2 wires from the transformer that go to the circuit board strip that holds the lights.3 volts leaves you virtually nothing left to run the LED's. They are current devices, not voltage devices. The voltage is used to overcome the P-N junction depletion layer...after that is accomplished, they behave like a short.

http://www.audiokarma.org/forums/showthread.php?t=146544

Post #7

[PakProtector]

hey-Hey!!!,
You'll still need a series diode to keep from reverse biasing them. It will flicker at 120 cps, but you'll not see that.
cheers,
Douglas

[Chazb11]

I also have an old receiver with 10vac to the lamps. I temporarily hooked up an LED from rat shack intended to run on 12vdc. (it has a little resistor inline) It lit up just fine. I didn't leave it in, it was just a "what will happen" sort of thing.
My question is would leaving this type of LED in my receiver damage the receiver in any way?

[James7506]

I used two surface mount LEDs to replace a power indicator in a tuner. Wired them parallel, inverse polarity with a series resistor. Would wire every two LEDs that way if I were to do over an entire piece. Jim

[Yankee Dog]

OK, so it looks like a lm317, a diode bridge, and a few resistors. I have used that led website before:

http://led.linear1.org/led.wiz

I have installed the leds using the 10 volts and a 470 ohm resistor at each individual LED. While this works, it's not a very "clean install".

Picture a long strip of circuit board about 1 1/2 inches wide by about 12 inches long. In that strip it has holes drilled in it for individual plastic sockets to be inserted with regular light bulbs in the socket. Half of the strip carries 10 volts ac on each side of the strip.

I was hoping to make the entire strip 3 volts on each side so I could just solder the led's to it (at the holes). I can still do it with the lm317 circuit instead of individual resistors at each led. I thought I could use one main resistor where the 10 volts of power coming from the transformer connects at the strip.

The flicker did not bother me. It was hardly noticeable. Kind of like the new led x-mas lights. You look at it, and something looks different, but your not sure what.

The white leds have a hint of blue to them and with this Nikko, it really enhances the tuner dial display. It is like the Marantz blue, but a little more intense.

I will try to post a pic later on. Thanks for the replies. YD