Repairing dim display on car stereo

[sandydoull]

Hi,

I have recently bought a car and the backlighting on the stereos display is pretty dim and virtually unreadable in direct sunlight, I am trying to figure out if there is a way to replace/repair the LEDs that would appear to produce the lighting in the display, this is how far I have gotten.

- I have taken the faceplate apart and measured the resitance on all of the bulbs and all are showing a resistance of 26ohms so this would indicate that no individual bulb is defective as such. Below are some pictures of the unit, I could just install a new stereo but i would prefer keeping the car's original unit

This picture is just to show the type of display in quesiton and is not my actual stereo on my unit the right hand side in pareticular is fading:

This is how the bulbs sitt in relation to the LCD which would suggest that they are acting as backlights?


This is a picture of the rear of one of the bulbs, they seem to be incased in rubber:


Anyone give any general advice on how I can troubleshoot this further and/or how to source new bulbs
Thanks in advance
Sandy

PS is there any simple way i could apply power to this board to test the bulbs with the unit dissmantled?

 

[Tha fios agaibh]

You can test them like a regular diode using you dvm, or could rig up a few batteries and probe say 3v leads across each led (observing polarity). As far as finding replacement leds, try digikey or similar online electronics site.

 

[Gryd3]

How bright do you want em? You could put replacement LED's in there, but if the circuit is designed to provide less than ideal current, you'll have new dim LEDs.
If you have a multimeter handy and a 12V source (Car battery, bench power supply, old computer PSU... etc) you can power up the head unit mostly assembled and see if you can read what wires provide power to that board and what voltage is supplied. You mimic this and your golden.
Once you power up the board you can measure how much current is supplied to the LEDs to find a replacement. You may also bypass the built-in LED circuit and provide your own supply to use any LEDs you desire. (Red Green Blue Pink ... etc.)

 

[sandydoull]

I'm not sure how I would go about powering it up partially assembled as the unit has a detachable faceplate, possibly be able to rig it up mounted in the car (dont have removal tool for the actual headunit).

A little update...on inspecting the LEDs I noticed that some had what looked like rust around the solder, so i went through each connection with my soldering iron and "re-soldered" the old solder, this had no affect whatsover, same dull display.

Does anyone know of an equivalent of Digikey that serves europe (Sweden)?

 

[Gryd3]

Check this list out: https://www.electronicspoint.com/resources/component-suppliers.34/

Can you supply pictures of the front and back of that board? We may be able to figure out where power comes in which will get you closer to powering it up.

 

[sandydoull]

Hi, I've gotten a bit further... was able to power it up in the car, and only two out of 5 bulbs were working no wonder everything was so dark! I rigged it up to where i could measure the voltage across a bulb where i noticed that the voltage is 12V with the engine off and 14v with the car running, i.e. dirent voltage from the cars battery?? I was not able to find the correct voltage bulb but tried a 3.2v 20mA for shits and giggles and of course it blew , so I need som "12v" rated bulbs right? Do these exist our local go to place doesnt stock a wide range, the bulb format is clear t1 3mm with straight wires which are inserted into rubber "condoms". Oh yeah, after blowing the bulb i somehow managed to short something when removing the dud and now none of my bulbs work (this didnt happen immediately think i might have touched a resistor with the soldering iron. The stereo still operates as normal. Sorry for the long post here's the pics HELP ME PLEASE!

 

[Gryd3]

Good job getting the voltage reading. I'm a little curious what had popped.
What's more is these seem to be 12V incandescent bulbs. Some of us assumed LED's.
When you desoldered one of the duds, did you accidentally cause a short with some solder?
Take a look at the components as well. Unless you held the soldering iron on a component for any more than a few seconds, it is probably fine. Make sure you didn't accidentally loosed it though.
(When you were removing the dud, was power applied?)

Also, can you upload a picture of the area of the board where you had removed the dud?
The bulbs appear to all be connected in parallel, and it almost seems like the + and - for them are provided on the second left pin, and right pin on the header from : http://i158.photobucket.com/albums/t85/sandydoull/DSC_000001-1.jpg?413

You can confirm this by using your multimeter and measuring from one side of the bulb, to those pins. If you have 0Ω, then it's connected (or accidentally shorted).

 

[sandydoull]

Answers in red below...

Good job getting the voltage reading. I'm a little curious what had popped. Initially it was only the new LED that burned (literally, smelled bad and smoked a little)
What's more is these seem to be 12V incandescent bulbs. Some of us assumed LED's. Would seem so, are these difficult to source
When you desoldered one of the duds, did you accidentally cause a short with some solder? I seemed to remember a drop of solder landing on a resistor but could have shorted something, didnt have the right equipment for removing solder
Take a look at the components as well. Unless you held the soldering iron on a component for any more than a few seconds, it is probably fine. Make sure you didn't accidentally loosed it though.
(When you were removing the dud, was power applied?) No, no power applied

Also, can you upload a picture of the area of the board where you had removed the dud? Get that for ya later
The bulbs appear to all be connected in parallel, and it almost seems like the + and - for them are provided on the second left pin, and right pin on the header from : http://i158.photobucket.com/albums/t85/sandydoull/DSC_000001-1.jpg?413 BTW does polarity matter when moutning new bulbs, for either type of bulb was pretty hard to tell which was +ve on the LED i tried.

You can confirm this by using your multimeter and measuring from one side of the bulb, to those pins. If you have 0Ω, then it's connected (or accidentally shorted). Uh you kinda lost me there, gonna read this again tomorrow when i remove the stereo again

What about replacement bulbs of the incandescent type, are these hard to source? I don't have any working bulbs at present so dont have anything to measure, before "shorting the bulbs" I only had one bulb left that was working, i borke another trying to remove it (glass broke)

Good job getting the voltage reading. I'm a little curious what had popped.
What's more is these seem to be 12V incandescent bulbs. Some of us assumed LED's.
When you desoldered one of the duds, did you accidentally cause a short with some solder?
Take a look at the components as well. Unless you held the soldering iron on a component for any more than a few seconds, it is probably fine. Make sure you didn't accidentally loosed it though.
(When you were removing the dud, was power applied?)

Also, can you upload a picture of the area of the board where you had removed the dud?
The bulbs appear to all be connected in parallel, and it almost seems like the + and - for them are provided on the second left pin, and right pin on the header from : http://i158.photobucket.com/albums/t85/sandydoull/DSC_000001-1.jpg?413

You can confirm this by using your multimeter and measuring from one side of the bulb, to those pins. If you have 0Ω, then it's connected (or accidentally shorted).

 

[Gryd3]

Let me dig some more later to make sure this is what you need.
There are many electronic e-retailers that will have these : http://www.digikey.ca/product-detail/en/8111/289-1222-ND/1552860

Polarity will not matter with incandescent, but it makes a huge difference for LEDs.

As far as probing the connecter on the faceplate to determine what pins are connected to the bulbs, I'll draw up a pic later as well.

Also do yourself a favor if you plan to do this thing more than once a year and buy a desolder pump, bulb or braid at radio shack or the source. This will let you suck up or soak up solder

 

[sandydoull]

Yeah I had a "solder removal pad" in my hand at the store but i cheaped out Thanks for all your help so far you've been a great help!

 

[sandydoull]

I ended up ordering some of these , had difficulty finding 14v rated bulbs close to me so i ordered these that are rated at 12v/60mA, how sensitive do you think these are with regards to voltage:- http://in.rsdelivers.com/product/rs/s1w050/t1-3mm-wire-terminal-filament-lamp-12v/3607913.aspx

 

[Gryd3]

I usually call things fine if there are within 10%. Using 12V bulbs with a source that could fluctuate up to 14.4 is a little much for me to be comfortable with personally.
If it works, it works. Perhaps someone else with more experience with incandescents can offer some insight into their tolerances.

 

[sandydoull]

Yeah I figured I'll give them a shot otherwise I need to wait a week or so for overseas delivery, I also ordered a desoldering pump

 

[Gryd3]

These are the two pins I'm thinking about.
You could use your multi-meter set to measure resistance.
Measure from one of the wires on the bulbs to the pins. One of the wires from the bulbs should have a 0Ω (Or very very close to) resistance to the right hand pin.
The other wire on the bulbs may be connected to the second pin from the left. I'm guessing based on the size of the wire trace. Most of the other pins seem too small, but it is impossible for me to trace, as the other side of the board is covered. When you ID the pins for the bulbs, you can also determine if you nuked something on the little board in the face-plate, or if you popped something within the DIN mounted stereo in the dash. (Hopefully not)
You could also potentially confirm the voltage and polarity on the pins by measuring voltage from the DIN unit in the car. This is only 'potentially' because power for the bulbs could be switched on when the faceplate is recognised, or could be damaged from the experiment earlier that caused the lights to stay out.
You already know what voltage those bulbs are expecting, so you could apply 12V to the pins once they are IDd to test the lights once you have new ones in.
Only do this after you have determined the correct pins, and polarity! Guessing with applying voltage can lead to releasing magic smoke from components that will never wake again.

 

[sandydoull]

Here's the picture of the area where i removed the blown bulb, the resistor directly above the bulb has a little dot of solder on it in the bottom right hand corner, could this affect things? Perhaps I managed to temporarily short across the bulbs poles while soldering but this shouldnt have blown the bulbs? Anyhow, I think i'll wait to get my desoldering pump and bulbs before jacking with this any further. I am afraid of breaking the stereo entirely, at least it still works at present (and we only have like two radio stations where i live so it's not that big of a deal tbh more of an asthetical issue

 

[Gryd3]

It's very difficult for me to see the dot of solder on the resistor. When you take pics, try to do it with the flash off. It gives a much more even lit photo without a hotspot.
Solder on the resistor will be no big deal. You just need to make sure it does not accidentally bridge any of the traces on the board, or accidentally short out any components.

 

[sandydoull]

[SOLVED] I got everything working now the 12V/60mA bulbs seemed to be working so far, had the car idling for about five minutes and nothing blew, dunno what happened when the other bulb blew I do actually remember dropping the board when i was removing the blown bulb so maybe that broke the other bulb. Again thanks for all your help here is a pic of my renewed retro stereo:

 

[Gryd3]

[SOLVED] I got everything working now the 12V/60mA bulbs seemed to be working so far, had the car idling for about five minutes and nothing blew,

Looks much better. Congrats.
Here's hoping they last a while for you, but if one of them goes again, you know it's easy enough to get in to fix em!