tscheucher
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Sep 17, 2009, 12:38 PM
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Re: [RevOsis] Teac 32" HD LCD TV Buzzing Sound - Repair Help
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Hello RevOsis!
Teac 32" isn't much of information, but I assume its a LCDV3253HD or equivalent for about 940 USD.
To answer your first question: The "yellow insulated (red marked)" part is a current limiting choke (transformer type) for the power supply's primary stage.
The new generation of switching power supply's come with a stepped up voltage in the time of startup - Therefore they took 450V - type elko's instead of the former used 400V types, which can be found in satellite receivers or other AV stuff.
I don't think that T3001 is faulty - It's rather one of the two high voltage film capacitors (C3004/C3003). You can try to replace those two to get rid of the humming, or how you said, buzzing noise.
The bad performance of picture and sound may have other reasons. Did you make sure you really baught the equal type of elko's for the three secondary stages. They must be 105°C low ESR types.
The second thing I recognized at looking at you uploaded picture, was, that some components leads are used as throughplating connections. That means that their leads connect the upper side and the lower side of the pcb tracks via solder bridges (jumps). I assume it's the same with some of the elko's. Make sure that they' re soldered on both pcb - sides where they need to be.
Take a hot soldering iron (80 Watts or above) an close the holes, where the elko's normally placed fully with solder. Cut off the leads of them to a length of about 7mm's. Hold them close to the pcb's positions and warm up one solder point - Than quickly push the first lead into it's position - Do the same with the other pole (lead).
After that leave a space between pcb an capacitor so that the solder can cover up also the top side of the pcb. Then solder the backside (solder side) of the pcb as usual.
In most of the cases it's not necessary to reolace the primary elko's (150µF/450V) unless the supply doesn't loose it's strength, which means that secondary voltages break down without visible reason. Try to connect the power supply for 2 minutes to the mains and than switch it off. Connect a common bulb to the leads of one of the big elko's. If there is still a voltage remaining after switchoff, that causes the bulb to burn, they need not to be replaced - Their capacitance hasn't been gone.
In the case that everything is working correctly now - perfect! - If there is also low performance present take a look at the photo couplers for a possible fault.
Good Luck!
(This post was edited by tscheucher on Sep 17, 2009, 12:43 PM)
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Teac 32" HD LCD TV Buzzing Sound - Repair Help
