Re: Sharp Mini Stereo CD-DD4500 LCD on the 'blink'
- From: "Arfa Daily" <arfa.daily@xxxxxxxxxxxx>
- Date: Thu, 29 Sep 2005 00:25:15 GMT
"NUMAtrekkie" <NUMAtrekkie.1w3bln@xxxxxxxxxxxxxxxxxx> wrote in message
news:NUMAtrekkie.1w3bln@xxxxxxxxxxxxxxxxxxxxx
>
> Hey folks, first time poster here.
> I have a Sharp CD-DD4500. Its well cared for and somewhere about 5
> years old. Well suddenly, the LCD display has crapped out. I get
> nothing but an almost imperceptible glow. It makes it darned hard to
> tell what I'm doing with the stereo.
> It is housed in a entertainment center cabinet with a glass door. I do
> notice that it gets rather warm in there, and I've plans to install a
> vent fan. Could this heat have had something to do with the problem.
> I imagine simply removing the heat won't fix it, so...any suggestions?
>
> Thanks folks
>
> Aaron, NY
>
>
> +-------------------------------------------------------------------+
> |Filename: CD-DD4500.jpg |
> |Download: http://www.diybanter.com/attachment.php?attachmentid=120 |
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>
> --
> NUMAtrekkie
Is it really an LCD, or is it a VFD ? LCDs are either back or side
illuminated, usually by minature incandescent bulbs, but sometimes by LEDs.
It's very common for these to fail.
VFDs, on the other hand produce light, and are usually a green/ blue colour,
although they can be any colour. To produce light, they need a heater
supply - typically 1.5 to 3v AC, and a negative supply of -25 to -32v. This
supply often goes low. It is usually derived straight from the mains
transformer via a voltage multiplier, which employs electrolytic capacitors,
which work very hard, having large AC across them all the time. They dry out
and go low value, the negative voltage drops, and your display fades away.
Sometimes, the heater is also fed via a capacitor, and same thing happens.
Easy place to check the negative voltage, is from chassis to either of the
display heater pins ( these are a pair at either end of the main pin row of
the display panel, and are separated from the rest of the pins by an extra
pin position ). The negative voltage can be measured here, because the
heater is floated on it, to reduce internal voltage differential between
display elements.
Some Sharp CD players from a few years ago, also used an LCD which was
backlit by a piece of electro-luminescent material. This needs a couple
hundred volts to light it up, and they used to have a little inverter on a
sub board to generate this. When the inverter went faulty, the display went
very dim. I don't think Sharp have used this for a while now, but just in
case ...
Arfa
.
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