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Swedx LCD XV1-19TVW - screen flash loop    
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ocf



Joined: 15 Jul 2016
Posts: 2
Location: England

PostPosted: Fri Jul 15, 2016 11:49 am    Post subject: Swedx LCD XV1-19TVW - screen flash loop Reply with quote

A friend gave me this TV to look at, it recently started exhibiting an issue, when switched on it appears to be stuck in some sort of burn in mode. The screen flashes in a loop between black, white and then RGB Stripes going from dark to light showing across the screen.

It definitely appears to be a test or burn in mode as there are no artifacts or other issues showing on the screen.

TV takes 12v DC external power

There were a few burst 220uf caps on the mainboard that I replaced but this didn't make any difference.

I cant find any schematics on the board or service manual, there are also no replacement boards form the usual sources.

Interesting thing to note, when I heated the board with a hot air gun and powered the TV on it did not show the colour loop and started up ok, I got the swedx splash screen and the TV accepted commands from the remote. After 10 seconds of staying on it immediately went back to the flashing burn in mode. Definitley something faulty on the mainboard, what would be affected by heat like this? I am thinking voltage regulators

I've located all the voltage regulators on the board they are all CX1084 and CX1117 and all labeled ADJ. I have taken a look at data sheets for the chip and I cant work out what voltge the Adjustable regulators should be outputting. Does the output voltage depend on the resistor used between Adj and Output terminls or do I have this all wrong

Voltage regulator part numbers I found on the board -

CX1084 ADJ 7226Y
CX1084 ADJ 7265Y
CX1117 ADJ 7382Y

One of the regulators is showing 0.15v on input pin, 0.9 on gnd and 2v on output, this seems wrong?

Dont vregs take a minimum voltage above the required output voltage to drive the regulator itself, so if this has 0.15v and 2v output surely its problematic?

I'm spitballing here, just trying to make sense with my limited knowledge

Any advice on what to check next? I have a good grounding in reading schematics and would consider myself far from a beginner when it comes to electronics, throw some ideas at me!

thanks in advance

OCF
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kuhurdler



Joined: 28 Dec 2006
Posts: 2852
Location: Overland Park, KS

PostPosted: Fri Jul 15, 2016 2:36 pm    Post subject: Reply with quote

if that regulator truly has higher output than input, it is not active.
JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Fri Jul 15, 2016 3:36 pm    Post subject: Reply with quote

Rework ball grid array IC (the one with the largest black heat sink in your pictures in the 'other' forum).
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