Brake light strip resistor identification

[GrahamMills]

Hi,

I'm trying to repair my car break light led strip.
The problem I have is the resistors are corroded as it leaked and filled up with water.

Can anyone help will identifying the value?

I've attached pictures but the colour is a bit hit and miss.
To the eye it looks like Orange, Green, Purple.

The are quite small and I can make out the direction as I can't see a tolerance band.

Any help is appreciated.

 

[kellys_eye]

Looks Brown, Blue, Black to me = 16 ohms.

Irrespective - if you figure out how the LEDs are wired (series, parallel or a combination of both) you can use a simple LED resistor calculator to determine what's required.

Show the whole board and, ideally, so we can see the tracks and how the LEDs are arranged.

 

[GrahamMills]

Hi, Thanks for the reply.
Looks like 4 banks of 3 in series.

 

[bertus]

Hello,

The leds look like the Vishay TLWR7600 or TLWR7900.
Those leds have a maximum current of 70 mA, where the usual leds only have 20 mA.
Looking at the board, it looks like 4 times 3 leds parallel in series:


Bertus

 

[kellys_eye]

Given the LED max current of 70mA it would be prudent to under-run them (for longevity) so a reduced current (say 50mA). At a nominal 12V supply (car battery) the series LEDs will need to drop around 2V to work properly.

Dropping 2V at 50mA means a resistance of 40 ohms. I suggested those resistors were 16 ohms and three in series would give 48 ohms - near enough what is required to run those LEDs safely.

You could put practically 'any' low value resistors in those positions (anything from 15 ohms to 33 ohms) and the LEDs would work. You'd be hard pressed to notice the difference in brilliance regardless of the resistor value used.

I'd suggest you get 18 ohm resistors (standard value) to reduce the overall current slightly. 0.25watt resistors will be fine. (16 ohm resistors are available but maybe not from your local parts store).

 

[GrahamMills]

Given the LED max current of 70mA it would be prudent to under-run them (for longevity) so a reduced current (say 50mA). At a nominal 12V supply (car battery) the series LEDs will need to drop around 2V to work properly.

Dropping 2V at 50mA means a resistance of 40 ohms. I suggested those resistors were 16 ohms and three in series would give 48 ohms - near enough what is required to run those LEDs safely.

You could put practically 'any' low value resistors in those positions (anything from 15 ohms to 33 ohms) and the LEDs would work. You'd be hard pressed to notice the difference in brilliance regardless of the resistor value used.

I'd suggest you get 18 ohm resistors (standard value) to reduce the overall current slightly. 0.25watt resistors will be fine. (16 ohm resistors are available but maybe not from your local parts store).

Thanks for the assistance, very appreciated. I'll have a rummage through my parts and see what resistors I can find.

 

[GrahamMills]

Just an update to say thanks and it worked. Popped in 3 x 18 ohm resistors and worked fine.

Graham