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LCD Screen Not Working Yamaha Hi-Fi System
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matt123



Joined: 12 Sep 2009
Posts: 6

PostPosted: Sat Sep 12, 2009 3:47 am    Post subject: LCD Screen Not Working Yamaha Hi-Fi System Reply with quote

Hi
The LCD screen on my Yamaha CC-5 Micro Hi-Fi system has recently stopped working. Here is a picture of it:

http://s631.photobucket.com/albums/uu40/matthewk0123/?action=view&current=IMG_3975-2.jpg

I have opened it up and found the LED used for the back light. Do you think that the problem is simply a blown bulb or something else? As the screen does not show up anything I'm not sure if it is back light related or not.

Any help or suggestions would be much appreciated.
thanks
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jts1957



Joined: 24 Nov 2008
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PostPosted: Sat Sep 12, 2009 5:21 am    Post subject: Reply with quote

You don't say if the unit works OK otherwise.

Most stereos with LCD displays that have a back light will work just fine without a backlight bulb. Just point a flashlight at display to read.
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matt123



Joined: 12 Sep 2009
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PostPosted: Sat Sep 12, 2009 5:47 am    Post subject: Reply with quote

thanks for the reply yes it works fine otherwise.
Ive tried shining a light on it but it doesn't seem to display anything.
thanks
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jts1957



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PostPosted: Sat Sep 12, 2009 6:01 am    Post subject: Reply with quote

Can you shine a light from behind? You're sure it's a LED (not a grain of wheat type lamp)? Is it mounted on a board (location #) or wired in?
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matt123



Joined: 12 Sep 2009
Posts: 6

PostPosted: Sat Sep 12, 2009 7:44 am    Post subject: Reply with quote

I tried shining a torch in front of the screen again and looking closely was able to just read it! thanks for the suggestion. Ive taken some pictures of the bulb and the circuit board:

http://i631.photobucket.com/albums/uu40/matthewk0123/IMG_3979.jpg
http://i631.photobucket.com/albums/uu40/matthewk0123/IMG_3981.jpg

I think your right, I think its probably a grain of wheat type lamp. There are two of them though so I'm not sure of the chances of both of them breaking?
thanks
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jts1957



Joined: 24 Nov 2008
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PostPosted: Sat Sep 12, 2009 7:59 am    Post subject: Reply with quote

Depends on if they're wired in parallel? or series? 4 wires/4-pin plug/socket, but can't see foils on the board it plugs into.
Regular lamps - if you have meter, unplug and test for continuity on each bulb - if both open put meter on AC Volts and CAREFULLY measure the same pairs of connections on the board/socket. If NO reading, try switching meter to DC Volts.
If you get a reading note it down. That will be very close to the Voltage of the bulbs. Amperage is usually 35mA or 70 mA. I'm assuming they're wired in parallel. (1 burnt out but you didn't take notice until the second failed.)
If you get NO reading AC or DC try to follow to where they end up in power supply area, probably open fuse/resistor.
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matt123



Joined: 12 Sep 2009
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PostPosted: Sat Sep 12, 2009 11:35 am    Post subject: Reply with quote

Thank you so very much for your help!
I took out the bulbs and using a magnifying glass found that they were both burned out. Ill try and measure the voltage on the circuit board tomorrow and try and source some new bulbs.
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jts1957



Joined: 24 Nov 2008
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PostPosted: Sat Sep 12, 2009 11:58 am    Post subject: Reply with quote

6, 8, 12 and 14 are the "common" voltages. 35mA and 70mA are the "common" currents. And then they have different bulb diameters. You CAN put a smaller diameter bulb in a larger hole or you can usually enlarge a smaller hole to fit a larger bulb (within a certain range). Wink
Select closest voltage. When you measure 10 volts, it usually is better to go to next higher (but may be dimmer). I like to keep a supply of ALL common miniature bulbs (8 types total) then I can try, and see the difference.
When wiring new ones in, cut old and new bulb wires at staggering lengths so splices (w/shrink tubing to insulate) are also staggered. 2 to 4 splices in all depending on whether board has them wired in series or parallel.
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matt123



Joined: 12 Sep 2009
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PostPosted: Mon Sep 14, 2009 6:37 am    Post subject: Reply with quote

Here is a picture of the old bulbs on the wire

http://i631.photobucket.com/albums/uu40/matthewk0123/IMG_3982.jpg

I'm guessing what you mean by staggering lengths is cutting the old bulbs off from each connecting wire at different points and then joining the new bulbs on by twisting the wires together?

Sorry but I don't know much about electronics Sad
Thanks again
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jts1957



Joined: 24 Nov 2008
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PostPosted: Mon Sep 14, 2009 12:46 pm    Post subject: Reply with quote

If you were able to obtain the exact replacement from Yamaha, it would just plug in. Probable ain't gonna happen.
Cut all 4 wire to SAME length, splice ends, solder and insulate - you now have one "blob" at one point along wires.
If you stagger splices the "blob" is eliminated (or you have 4 smaller blobs, if you want to look at it another way).
Splicing: http://www.mmxpress.com/technical/connections.htm
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