How to fix an LED backlight
 

I have a car stereo front panel (model: Panasonic CQ-DFX572N mp3 player)
in which the display suddenly stopped working the other day.

I'm not much of an electronics buff, but on opening it carefully, I can
see that there is a large plastic backlight (presumably an LED?) the
size height and width of the whole front panel that sits behind an LCD
'mask' which then lets through the blue light to display the text,
giving a blue text on black background effect. The blue backlight also
liights up some front panel buttons and the area around the volume knob.
The only front panel light the currently works is a red one, and
therefore must have its own LED/backlight.

I plugged the naked circuit board into the car stereo head unit and saw
that the LCD screen still works, it's just the backlight that is broken.

I can see what I'm sure are the the two solder points on the back of the
PCB that correpsond to the backlight. They look OK, although by that I
mean the solder points don't seem to be loose or dirty.

So all that's broken is the backlight.

Questions:

Are these types of backlights just LEDS?

Do they normally have fuses, is this what might have blown?

Is this easily fixable, is there anything I can try given that a new
front panel is almost the same cost as a completely new stereo?

yes typically these are standard incandescent lamps, what a bummer, if they
had been leds you would not probably be changing them, they are 12volt
mini lamps avail at radio shack, get some, desolder the dead one, solder
the new one in its place, and get the color cap off the old bulb and put
it on the new one. good as new or at least for a few more years! id change
the good one also chances are you will put it all back together and 2 days
later it will be dead

Mothra wrote:

I have a car stereo front panel (model: Panasonic CQ-DFX572N mp3 player)
in which the display suddenly stopped working the other day.

I'm not much of an electronics buff, but on opening it carefully, I can
see that there is a large plastic backlight (presumably an LED?) the
size height and width of the whole front panel that sits behind an LCD
'mask' which then lets through the blue light to display the text,
giving a blue text on black background effect. The blue backlight also
liights up some front panel buttons and the area around the volume knob.
The only front panel light the currently works is a red one, and
therefore must have its own LED/backlight.

I plugged the naked circuit board into the car stereo head unit and saw
that the LCD screen still works, it's just the backlight that is broken.

I can see what I'm sure are the the two solder points on the back of the
PCB that correpsond to the backlight. They look OK, although by that I
mean the solder points don't seem to be loose or dirty.

So all that's broken is the backlight.

Questions:

Are these types of backlights just LEDS?

Do they normally have fuses, is this what might have blown?

Is this easily fixable, is there anything I can try given that a new
front panel is almost the same cost as a completely new stereo?

You probably have a EL display. No, there NOT leds. They take a higher
voltage to make them work. Typically 40 to 100 volts.
If there is a higher voltage at the terminals and its dead, the display is
bad. If not, the power inverter the supplies the display is bad.

Bob



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"AshTray700" writes:

yes typically these are standard incandescent lamps, what a bummer, if they
had been leds you would not probably be changing them, they are 12volt
mini lamps avail at radio shack, get some, desolder the dead one, solder
the new one in its place, and get the color cap off the old bulb and put
it on the new one. good as new or at least for a few more years! id change
the good one also chances are you will put it all back together and 2 days
later it will be dead

Or do what I usually do - replace them with high brightness LEDs and
a suiltable current limiting resistor.

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that usually works great for me also, i went through my oldsmobile and
changed them, its strange that they still use typical bulbs in these
devices when led lamps will outlast the device and use much less current
(they do it for cell phone displays), i guess that is just the "built to
die" principle that manufacturers use these days. if just one stereo
manufacturer would really build consumer level electronics and design them
well it seems to me that they would take over the consumer electronics
market anyways im rambling , if you want to use led lamps you can go to a
hoopers parts supplier if one is nearby and the led package should give
you the resistance you should use in a 12v system. the cheapest way i
found to get a good bright white led is to get one of those keychain
lights for about $4 or go to http://www.superbrightleds.com/ and you can
order them

You probably have a EL display. No, there NOT leds. They take a higher
voltage to make them work. Typically 40 to 100 volts.
If there is a higher voltage at the terminals and its dead, the display is
bad. If not, the power inverter the supplies the display is bad.



I've never seen an EL panel used in a car stereo, might be some that use it,
but most just use small incandescent bulbs, why I have no idea since LED's
have been quite mature and inexpensive for a while now.

yeah, the only types of displays used in the car stereos that i have seen
are lcd with backlight bulb (most common),lcd with indiglo type display
(rare cause its not very bright, ive only seen a few like it), and the
sealed glass with flourescent priniting in it display (on many factory car
stereos but not that many aftermarket ones) and of course there is that
led display block but thats almost a thing of the past now (we have
washing machines that now have plasma screen displays with animations, god
talk about overkill!)