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is anyone here an electronics super hero?


dazzer-b

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hi,

 

recenlty changed all the led's in my interior to white ones (which looks awesome) ok my soldering skills arent amazing but majority of them work great, only ones giving me grief are the ones in the oil pressure gauge in the center pod, they start up fine but after maybe 20 or 30 mins of driving all the leds in that pod go out even the red one i didnt change which lights up the needle, could this be because they run in series and if one end isnt correctly soldered they all go out or do you think something has a thermal cut out which is why they only go out after a certian time. if i turn the ignition off and back on again it will still be out, its usually the next day i notice they are back up running ok

 

cheers

 

dazzer

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You’ll have to bear with me as its years since I did electronics seriously.

 

Sounds like you have a "dry" solder joint to me

A led usually takes a current of approx 20mA (0.02A). If you connect say 3 in series then the same current will run through each of them.

So if you have a soldered “dry†joint (ie solder not fully adhered to the wire producing a high resistance) then its likely to go high resistance if moved and turn off all leds. By the way you did connect a suitable resistor in series with the led’s to limit the current ?

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You’ll have to bear with me as its years since I did electronics seriously.

 

Sounds like you have a "dry" solder joint to me

A led usually takes a current of approx 20mA (0.02A). If you connect say 3 in series then the same current will run through each of them.

So if you have a soldered “dry†joint (ie solder not fully adhered to the wire producing a high resistance) then its likely to go high resistance if moved and turn off all leds. By the way you did connect a suitable resistor in series with the led’s to limit the current ?

 

LEDs are already in place. It's PCB mounted stuff as far as I know. I'd hope you'd replace like for like and change the colour.....

 

 

I think I'd be removing the board and at least removing then resoldering the new LEDs. I'd then be bench testing it to see if the problem still exists.

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no i didnt, the guide i was going by gave me exact led part numbers that work and said only change the resistors if you require a higher light output, now you have said that i do recall when i was unsoldering the existing ones i did take out one of the legs that id need to solder back onto by accident, but i assumed the solder would creep into the circuit board and make a good enough contact. would that nmake them all go out though

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no i didnt, the guide i was going by gave me exact led part numbers that work and said only change the resistors if you require a higher light output, now you have said that i do recall when i was unsoldering the existing ones i did take out one of the legs that id need to solder back onto by accident, but i assumed the solder would creep into the circuit board and make a good enough contact. would that nmake them all go out though

 

yes

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If any part of the series connections results in a dry joint then all led's will be affected. Don’t understand your description “where as the existing were 1+ and 3-,â€

Leds usually have only two connecting wires (your not talking about surface mount stuff are you) one slightly longer lead (+).

As rtbiscuit says dry joints are hard to spot. I would suggest reheating all the joints you’ve touched and run a little more solder onto them.

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yeah on the main circuit board! under each existing led wads 4 solder points apparently 3 were - and 1 was +, so i had to move the led's up slightly so that i wound only connect onto 1+ and 1- if that helps.but where there were 4 little metal squares to solder to i think when i removed an old led i scrapped the more accidently and took the matal square ( sort of like foil) straight off the board but thought that it will connect via a pin of somekind onto the circuit board, just wierd that they work alot of the time thats all.

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yeah on the main circuit board! under each existing led wads 4 solder points apparently 3 were - and 1 was +, so i had to move the led's up slightly so that i wound only connect onto 1+ and 1- if that helps.but where there were 4 little metal squares to solder to i think when i removed an old led i scrapped the more accidently and took the matal square ( sort of like foil) straight off the board but thought that it will connect via a pin of somekind onto the circuit board, just wierd that they work alot of the time thats all.

 

If you have a dry joint and it seems likely that you have, then the led operation will be intermittent. As the joint flexes its resistance changes (usually goes higher) and will reduce the voltage to the led’s (brightness will vary) If it goes high enough (and it would) then all the voltage is dropped across the joint leaving nothing to light up the leds.

I very much doubt the prob has anything to do with temperature.

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Liked your idea about changing the colour of the panel lights so been doing a bit of research and found you can get Tri colour led’s (you may have already known that. I didnt) which have three leads coming out from them. Internally there is one red and one green led. If both are on together then it appears yellow. So your led;s may be tri colour. The longest lead is common (cathode) and the other two the respective led anodes.

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To be honest trying to solder onto all 4 of them terminals would put me off big time tbh, I struggled just onto 2 pins, they are literally 1mm apart and trying not to get the solder a cross 2 pins would be so hard. Apart from that it was ok doing the job, ordered new dials from the USA and the LEDs were dirt cheap might of cost about £150 max and a days worth of soldering. Didn't need to do the stereo though.

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