#16
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Those inverter transformers operate at high voltages, and they are prone to insulation breakdown and shorted turns, which then overheat and blow the driver FETs. By the time you source the parts (if you can get them) and install them, you might be best off looking for a used board on eBay.
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#17
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A backlight fault on these doesn't shut the power supply down. The set would power up normally with no backlight. The glass diode is a Zener and often shorts on these, from memory it's 5.1V. It will shut down the power supply if it has failed. If it has shorted also replace the 2 10V 1000uF caps (unless they test good with an ESR meter).
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#18
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Those are the 2 caps i was talking about replacing, i was thinking of replacing them with 16v ones.. Im uncertain about the zener being shorted, i hook it one way, and the digits begin to climb as if ive hit a capacitor in the circuit. my meter isnt zeroing out when i test it. The numbers are low but not zero... I'll have to test it again to be sure.. Ide hope the backlights are okay, this set has less than 30 hrs on it as stated earlier
SR Last edited by Boobtubeman; 07-06-2016 at 09:55 PM. |
#19
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It is fine to replace the 10V caps with 16V caps. The zener diode will read close to 0 in both directions if it is shorted. Otherwise it will read around 0.7V (using the diode check range on a digital meter) in one direction and open in the other. In circuit other components around it can effect the reading. If you're unsure unsolder one side of it and test again.
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#20
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Quote:
SR Last edited by Boobtubeman; 07-10-2016 at 12:39 AM. |
Audiokarma |
#21
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Went as far as running without the zener and no change. The to-220 tests fine on the diode setting on my meter so its back in circuit. Double checked my voltages and all the + and- 5 volts are present. The 12v pin only gets as high as 3v before it falls due to the instant shut down.. Swapped the 1000uf@10v e-caps with an exact set of used ones. I dont have an ESR meter, I am using a centech #69096 digital meter if that helps reference my tester and its functions...
The dc-dc sub board mentioned gets to 14v before the shutdown... any other culprits on this board i need to check?? SR |
#22
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I don't have one in front of me right now to check, nothing immediately obvious jumps to mind. Have you tested with the 12V line disconnected from the main board to rule out a fault on the main board dragging to down? I've seen this when the audio amp IC fails.
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#23
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Mainboard is fused and they check OK, however, i did remove the 12v lines to all and the result was the same. Its definitely within this board somewhere.. I dont know if the 12v rail is okay, it never reaches 12v before shutdown, but i gained 2 volts without a load, meter reaches to 6v before cutoff... Definite head scratcher this one be...
SR |
#24
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There's a Zener on the 12V rail hiding between a couple of caps under a blob of silicon on the one that I have on the bench. There's a FET on the bottom of the board but I don't think it's on the 12V rail. I've tried tracing these out further in the past and hit a dead end with the unmarked (or unreadable) SMD parts on the bottom on of the board. At that point you're already into it for more than a 26" LCD TV is worth.
If I get time I'll have another look at the one I have here, I don't remember what was wrong with it. |
#25
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No worries... It was a freebie and my first look inside one of these flat screens. Definitely a great learning experience and i appreciate you folks walking me through it. I can see why there are no more tv shops in my town...
Been looking on ebay for the local board offerings and searching for a cheap one, first im gonna exhaust myself on this one before then. Ill check that zener next and do some more poking around.. Thanks.. SR |
Audiokarma |
#26
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Upside??? i did get a board of Ebay...... Downside? My board is in better shape, The replacement i ordered has NO output voltages at all (yes, i confirmed voltage going into it )
Since i dont have an ESR, i think ill make a trip to the store and go FRESH caps for the old board and see what happens.. SR |
#27
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Quote:
https://www.amazon.com/Yosoo-Display...W7SKV0QNA8K8G9 not affiliated, jr |
#28
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Quote:
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#29
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Replaced the 1000uf-10v with 35v ones and still wont come out of standby. Still beats the DOA board i got off ebay
Back to the ole drawing board....... SR |
#30
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Got another board and STILL wont come out of standby.... Any way to kick the power supply on without hooking the tv works up to it? Also i noticed a green led on the power board, in what situation will this light??
SR |
Audiokarma |
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