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#1 |
Badcaps Veteran
Join Date: Dec 2009
City & State: Prague, 50°4'52.22"N, 14°23'30.45"E
My Country: CZ
Line Voltage: 230 V/50 Hz
I'm a: Knowledge Seeker
Posts: 4,436
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![]() Display only blinks and than stays dead. Check open the PSU revealed it is dead.
There are three output rails: winding to feed the TEA1791T synchronnous rectification controller (this thing has no connection with primary side!), the output for the rectification transistor - this rail feeds the signal board, and than backlight rail. Seems like the unit only pumps few cycles to the secondary so voltage rises a bit and than falls down as the caps discharge. I have about 15.5 V on a small cap on the primary auxiliary rail just after the diode which slowly falls, pumps again to 15.5 V and that repeats. There is however oscillating voltage between like 18 and 19.6 V on the cap directly in front of the primary common PFC/PWM controller. Do not think this is normal condition. Cannot identify the controller right now, it has layer of lackquer, gonna have to try removing it. I do see only 320V on the input cap though, there is no spike suggesting the PFC would be turning on, so maybe the problem lays in here?
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#2 |
Badcaps Veteran
Join Date: Dec 2009
City & State: Prague, 50°4'52.22"N, 14°23'30.45"E
My Country: CZ
Line Voltage: 230 V/50 Hz
I'm a: Knowledge Seeker
Posts: 4,436
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![]() It's very difficult to read anything in here but it seems like the PFC/quasi-resonant flyback controller is NXP, possibly TEA1751T. According to the datasheet, the startup voltage is 21-23 V so when it's at 18-19.6 that's too low.
The path goes from the auxiliary winding on primary side through inductor to an SMD diode, capacitor and than there is "K415 C200" TO-92 bipolar transistor. The 15V feed leads to its collector, the oscillating 18-19.6V output is on its emitter. Collector and base has 1002 SMD resistor in between and base is also connected through an SMD zener to return. So it seems like some amplifier with zener feedback? And this is to feed the Vcc of the controller. |
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#3 | |
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Join Date: Feb 2012
Posts: 8
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#4 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
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![]() If we can see some good clear pictures of the boards and how they are connected together, that will be a good starting point.
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Never stop learning Basic LCD TV and Monitor troubleshooting guides. http://www.badcaps.net/forum/showthr...956#post305956 Voltage Regulator (LDO) testing: http://www.badcaps.net/forum/showthr...999#post300999 Inverter testing using old CFL: http://www.badcaps.net/forum/showthr...er+testing+cfl Tear down pictures : Hit the ">" Show Albums and stories" on the left side http://s807.photobucket.com/user/budm/library/ TV Factory reset codes listing: http://www.badcaps.net/forum/showthread.php?t=24809 |
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#5 |
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#6 |
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#7 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
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Line Voltage: 120V 60Hz
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![]() SO, what Voltages do you have on that white connector of the power supply board that goes to the logic/main board?
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#8 | |
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Join Date: Feb 2012
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![]() Quote:
Thanks for your answer I have no light on the front power push button. I tested the general 220v power switch on the back, and the fuse. And to answer your question, I have 0v on each wire on the white connector, with the board plugged or unplugged: https://www.youtube.com/watch?v=8uVT8g2OchQ I have 335Vdc arriving to the "120µF / 450V" capacitor, and I unsoldered it and tested it too: https://www.youtube.com/watch?v=IL7uwboCR70 Hope I done everything right, and made myself understood, English is not my first language. Thanks |
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#9 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
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Line Voltage: 120V 60Hz
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![]() In your picture #2 on the bottom left, there is an IC (18-PIN?) there, can you read the P/N?
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#10 |
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#11 | |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
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![]() Quote:
NOTES: You will be working in the HOT DEADLY side of the circuit so do not touch ANYTHING with your hands or body, you should at least plug the monitor into GFCI outlet. |
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#12 | |
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Join Date: Feb 2012
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![]() Am I right for where to test? ![]() Last edited by fred41; 05-16-2018 at 12:56 PM.. |
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#13 |
Badcaps Veteran
Join Date: Jan 2014
City & State: Point Fortin
My Country: Trinidad & Tobago
Line Voltage: 125VAC 60Hz
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![]() GFCI means Ground Fault Circuit Interrupter. This is an electrical outlet with Reset button and a Test button on it that should a shock hazard be detected it would switch the supply to the receptacle OFF.
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#14 |
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#15 |
Badcaps Veteran
Join Date: Jan 2014
City & State: Point Fortin
My Country: Trinidad & Tobago
Line Voltage: 125VAC 60Hz
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![]() This is how our electrical GFCI outlets look like. The RED button is the RESET and the BLACK button is the TEST. So is a fault is detected the RED button pops up and disconnects the supply and to reset is to just push it back in. When the Test button is depressed the RESET button pops up and so we know the system is working.
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#16 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
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![]() EURO GFCI outlet:
http://internationalconfig.com/icc6.asp?item=4721-10HG2 |
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#17 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
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Line Voltage: 120V 60Hz
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#18 | |
Badcaps Veteran
Join Date: Jan 2014
City & State: Point Fortin
My Country: Trinidad & Tobago
Line Voltage: 125VAC 60Hz
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#19 | |
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Join Date: Feb 2012
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![]() Quote:
And I didn't blew up the house, nor I burned myself... Thanks everyone |
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