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Yamaha Yzf R125 Speedometer Led Mod


Guest Remas

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Guest Remas

Hello there everyone.

I got my R125 about a month ago and I decided I'd like to modify the backlight of the speedometer after I saw one modified in a video right here (0:18 - 0:21).
https://www.youtube.com/watch?v=lPDX0Rde7JE

I bought SMD 3528 Blue LEDs off ebay and I swapped the original ones with the lovely blue LEDs.

I noticed something very weird happening and this is the reason for me creating this thread. I swapped all LEDs related to the backlight of the screen and tachometer. It turned out that all of them were glowing but very dimly. I decided to start again and swap one LED at a time. I numbered the LEDs on the picture right here
[img height=900 width=1200]
When I replaced LED 1, everything was great. It was very bright and everything seemed to be okay. Then as I was very impatient I swapped LED 2,3 and 4. Here is the result
[img height=900 width=1200]
[img height=900 width=1200]
As you can see LED 1 and 4 are very dim. LED 2 and 3 are good. LED 5 and 6 are okay (they haven't been swapped) but as you can see on the picture they are dimmer than LED 7 and 8.

I decided to take the voltage readings and here they are:
LED 1 = 2.46 V
LED 2 = 2.90 V
LED 3 = 2.90 V
LED 5 = 1.78 V
LED 8 = 1.87 V

My question is what can I do to make all LEDs glow bright? Is the resistors beside LED 1, 4, 5 and 6 that need to be replaced/removed? (There are no resistors at LED 2 and 3 and the voltage is high and consistant) Maybe it's something else?

I tried to contact the guy that made the video but i had no response, that's why I'm posting here.

(I know the soldering isn't perfect and that i didn't clean the flux off.)

Thank you for checking this thread out.

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Let's get this straight: you're replacing red LEDs with blue ones right?

If so, it's no surprise it'll be dimmer: the human eye is less sensitive to blue light (although this is somewhat negated by the fact blue LEDs are very bright) and the higher voltage drop means less current will flow, given the same series resistor. You can increase the brightness by reducing the series resistor but check the LED datasheet to be sure you're not exceeding the current rating.

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Guest Remas

Thank you for your reply.

In this case this has nothing to do with how the eyes see it. As you can see on the picture as well as if you look at the Voltage values below the picture you will see that LED 1 and 4 is dimmer because the voltage is lower. I will have a look at the resistors and see which ones I can replace them with.

Thanks for your help. I will write again once I try it out (gonna be a little while because I'm waiting for my new soldering station to arrive)

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