Semiconductor Expert?

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MURICA
I am trying to troubleshoot and replace a few LEDs on a taillight of Honda.

Circuit board says: N27, as well as SA64845NZ27A and QPWG-N544 .

It's a RED LED, can it give any pointers on the type to get from mouser or similar place? Thank you (y)
 
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860
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Reno, NV
I think you will have a hard time trying to find out the original part number. If you can test one of the good LED's with a variable power supply and find out the number of mA and volts it takes to light it up, you should be able to find a replacement at Mouser.
 
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5,909
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San Francisco Bay Area
I'm guessing that you can replace the entire unit, but choose not to? I thought that one of the benefits of a large array of LEDs is that if one or two fails, it still works as intended. I see a lot of traffic lights with several dead LEDs. Any way to test it for voltage across the LEDs when it's working? I guess the biggest problem would be in getting ones that are of similar output. Not only that, but LEDs inherently degrade/dim with use. Incandescents do too, but not quite like LEDs. A new one might look way brighter than the existing ones.

I could find this which referenced one of the codes:


As a semiconductor guy myself, I wouldn't say this is really a question in need of a semiconductor expert. More a circuit board or bill of materials expert (of which I'm not).
 

maverickfhs

Thread starter
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Yes that was more of the export BOM on the Honda side, did see this reference while looking it up :)

New board is quite expensive, have already ordered a used one which as per seller is a working one, but want to see if existing one can be fixed.

If not, no big deal and will just swap it out with the 'used one'.
 
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11,563
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Illinois
Wonder if you would be better off with another unit that may also have SOME non-working LEDs and just harvest the same components from the one with the most failed to make one good unit.

That way, you have the same component and likely a source for additional LEDs when they fail in the future.

Have you confirmed the LEDs have failed and not the soldier joints?
 

maverickfhs

Thread starter
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Actually one of the LED is just plain missing from the circuit board but otherwise all test good and light up using multimeter diode function.

Does it mean solder joints are bad and needs to be cleaned or re-done?
 
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11,563
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Illinois
Without laying an M1A1 Eyeball on it, it's hard for us to say. It's just one of many possible failure modes.

Actually one of the LED is just plain missing from the circuit board but otherwise all test good and light up using multimeter diode function.

Does it mean solder joints are bad and needs to be cleaned or re-done?
 

maverickfhs

Thread starter
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2,721
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MURICA
So maybe a good idea to keep this LED board as a spare and re-use whenever any other LEDs go out.

Instead of spending time and energy on it. Thank you all (y)
 

MolaKule

Staff member
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Most LED's in cars are 'jumbo" 10mm LED's.

A single led requires about 3.1 volts across it (out of circuit of course) and about 20 mA of current. Longer lead is positive and shorter lead is negative.
 
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Most LED's in cars are 'jumbo" 10mm LED's.

A single led requires about 3.1 volts across it (out of circuit of course) and about 20 mA of current. Longer lead is positive and shorter lead is negative.

Depends on the LED, but the standard ones that have been around for 45 or so years are around that voltage. Newer surface mount LEDs (fairly common in replacement bulbs) are often less than that.

88-red.jpg


We used LEDs like these back in our breadboard projects. They would just plug right in, but often we would trim them do they didn't stick out so much. I tried driving it straight from a TTL output, but there were some buffers and TTL that was meant for driving LEDs. I forgot what those were called.
 

MolaKule

Staff member
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21,716
Location
Iowegia - USA
Depends on the LED, but the standard ones that have been around for 45 or so years are around that voltage. Newer surface mount LEDs (fairly common in replacement bulbs) are often less than that.

88-red.jpg


We used LEDs like these back in our breadboard projects. They would just plug right in, but often we would trim them do they didn't stick out so much. I tried driving it straight from a TTL output, but there were some buffers and TTL that was meant for driving LEDs. I forgot what those were called.

Right some are SMD (Surface Mount devices) and not seeing the LED board in question it sounded as if he could de-solder the LED, a "through hole" LED which means it has long leads as in your picture above.
 
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5,909
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Right some are SMD (Surface Mount devices) and not seeing the LED board in question it sounded as if he could de-solder the LED, a "through hole" LED which means it has long leads as in your picture above.
Surface mount is going to be a huge pain to desolder and resolder. They're usually baked in ovens to get the solder to flow. I recall when my company would pay to have someone do rework on a prototype board.

I have the feeling that these were designed just to be tossed if they no longer work.
 
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Under the hood
Those appear to be similar to 5mm square "pirhana" LEDs, but from the picture, may have an extra pin for a discrete high/low setup instead of using PWM inside a controller to vary the brightness. If that is the case, that will make them harder, if not impossible to source, as proprietary, non-standard components.

The pirhana LEDs were common building blocks for people who fabricated their own retrofits, so you may find more useful info from the forums where they are discussed, like hidplanet.
 
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