Hi all you fine-wire saavy unicyclists.
I have a well-used tiny DVD player. One of those folding ones that has a 7" screen to keep the kid quiet on long road trips.
The sound went out, sound goes to headphones fine, and to external speakers, so I am thinking it is NOT the sound card, but a loose wire between the speakers and the soundcard. Does that make any sense? The speakers are on the monitor and so the wire goes through a hinge. I think this is a lousy design flaw (especially now that it’s broken ).
I opened up the monitor half and tightened up some screws that had simply fallen out on the interior that were associated with the hinge mechanism but all the wires to the speakers looked just fine. I shut that back up and no change in the operation, except the hinge mechanism works correctly now.
When I look at the other half of the device, wanting to open it to look for wires, I read HIGH VOLTAGE expert operators only. How seriously should I heed this warning? Can I unplug it and let the capacitors zero out over night and be fine?
That’d be my first guess, too. Will it play with the screen open to different angles? If so, wiggle it around and see if it retouches a broken wire in the hinge. That might betray a broken wire.
Whether it works or not, trace the wires back to the board, (make really sure you have the right spots) and check for sound.
Don’t touch circuits if it tells you there is high voltage. There isn’t any need for high voltage in there, but it’s just a good idea to avoid contact with the circuits anyways. Most likely the warning is for the AC adaptor input, just for the extremely remote case the wall transformer should short. But if it makes you nervous, electrical tape over the nonrepair areas wouldn’t hurt anything.
More safety info at: http://www.repairfaq.org/sam/odfaq.htm
If these wires tie into the same traces as the headphone jack, that just makes the fault obvious. (IOW, the same source is used for both) This is probably the case, but otherwise:
Try probing with a digital AC voltmeter and fiddle with the volume adjustment to see if the signal goes up and down.
If there’s signal at the board, grab a soldering iron. No more than 80 watts, so as not to cook anything. Use 1/16" rosin core solder for reconnecting things, the silver stuff isn’t necessary for this job. If you can get at the back of the speaker, disconnect the wires, (unplug or melt the solder joint with the soldering iron) and try probing the speaker’s connections with a AA or AAA battery and wire scraps/bent paper clips, and listen for the “tap” from the speaker. If the signal’s good at the board, and the speaker works, then it’s time to try new wire. Test lead wire (like for a multimeter) is made to be bent a lot without breaking, and makes an ideal replacement. The more strands in the wire, the better it’ll hold up to bending. Tin the wire ends before soldering to the board or speaker, it makes the soldering go much easier, with less chance of burning anything.
If you need to desolder, my favorite method is desoldering wick. It’s stranded copper braid that’s soaked in rosin; touch it to a solder joint with a soldering iron and it just sucks up the solder. Radio Shack should have some.
Check any soldering with a magnifying glass to make sure solder doesn’t bridge any connections, or that the new connections didn’t crack during cooling. Before and after all the work: there is a small chance that a bad solder joint is to blame for the trouble!
You can do it, it just takes a little patience!
Hi Wobbly John,
Thanks for the very clear directions. I will print them up and will follow thru on them soon. I’ll have to get a meter, but that’s something I’ll need anyhow.
It’s a nice little appliance to have, so I will try to fix it. If I can’t, the kid will just have to use his headphones!
Most LCD screens are backlit using a cold-cathode fluorescent lamp (CCFL). In order to induce light, a very high voltage must be applied. This is typically around 1000 volts! Though there is minimal current associated with the voltage, it is possible to be hurt or killed by it.
While I’m here and we’re talking about this, an even more dangerous appliance to open and poke around in is a vacuum-tube (CRT) television or computer monitor. Even when unplugged, the capacitors within these devices will hold a lethal charge for days!
It sounds like you have no reason to go near the “high voltage” circuitry anyway. Like I said, it’s for the backlighting - and your problem lies elsewhere. Wobblyjohn has furnished excellent instructions.
I wasn’t aware of the backlit screen bit! Thanks for the link! I’m falling behind in this electronics stuff. I’ll be sure to do more thorough Googling before assuming, especially if it’s advice.
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I wasn’t aware of the backlit screen bit! Thanks for the link! I’m falling behind in this electronics stuff. I’ll be sure to do more thorough Googling before assuming, especially if it’s advice.