Re: Powersupply proble, SAMSUNG LA32R71B
Hi all,
Finally this TV was fixed up. The problem was exactly the chip "F9222L". It took me nearly two months to get this chip from China (I asked one of my friends there to order it for me, cheap of cause). Once this IC changed, problem solved.
Thanks for all of you who gave me hints and information.
vikingchow
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Last Activity: 09-12-2011, 06:17 AM
Joined: 08-01-2010
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Re: Samsung LCD LE40R86 no picture
What is the main/b's part number?
P.S.
It's good to have two identical item for checking error etc, saves lots of time.
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Re: TOSHIBA 32" LCD Vertical Lines
thanks for your advice, I will check the power later....Leave a comment:
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Re: TOSHIBA 32" LCD Vertical Lines
There are two ribbon connectors from logic board to the panel, I removed the left one then the left half of panel went black,the other side remained the same picture as before, same thing happen with the right side. Reconnect them, back to what it was. Does this mean the faulty is in logic board?...Leave a comment:
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TOSHIBA 32" LCD Vertical Lines
Any idea about what's going on with this LCD TV? Photo attached.
How should I determine it's the logic board's problem or the LCD panel?
Many thanks.
Viking... -
Re: Powersupply proble, SAMSUNG LA32R71B
Now I think it's because of ICP801S, another switching controller, its drive Pin only offer about 10% dutycycle PWM when modulating, and most of the time doesn't output modulating pulses at all. Base on the first page of schematic, the PSU DC outputs would not affect its duty cycle, only a voltage divider across 380V DC line gives this IC voltage feedback.
Voltage on RP814 now measures 2.5V which is alright, RP819 has right value of resistance also. Vcc(Pin8) is about 15V, very clean and stable(I have disconnected RM801 so no...Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Yes I have checked the feedback loop. Reference voltage of '431 was ~1.5V, because that 24V output had dropped to 16V.
I have no way to measure the transformer windings' inductance. But could you look back to my #8 post, the main switch circuit before the PFC switching waveforms doesn't look right, does it?Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Now found that the noise on ICs' Vdd was from PFC circuit, I disconnected this part by desolder the resistor RM801, noise gone.Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Windings' waveforms are all like full duty cycle... I already checked the feedback circuit and changed KA431 and the opto-coupler as well, not their problems.
Come back to my previous suspicion, QP801S, the main switching MOSFET is not modulated as I expected. I looked at the switching IC, ICP801S, its power supply was a bit noisy, followed this track, found the stand-by power switching IC's power supply was noisy also(IPS801S). Noise ripple was about 5V. Pretty sure its not filtering caps' problem....Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Then I measure the switching component before the PFC module, see attached pics.
Looks like some weird things happening here? It is not modulated properly, the 1st pic is QP801S Gate pin, 2nd one is Drain. The 3rd one is also Drain but in bigger time scale.
This MOSFET is not modulated in full time, just like a "part time" working guy. However CP812 still gets a smooth 380VDC.
Anyone can tell me this is normal or not?...Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Vcc Pin of F9222L shows a very clean 17.5V, and those caps are both looking alright.
Just found this chip's block diagram on internet, see attachment1. I measured pin 20 and pin 19 with a scope, see attachment2&3. It seems the IC is modulating output voltage at full duty cycle, but output still too low....Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Yes, things become complicated where the PFC part added. Worse that I can not find the datasheet of F9222L and have no idea how it works. I had check all pin out resistance vs ground of this IC, no obvious short to ground though. Could you find the link of the reported F9222L problem so that I can have a look please?
Thanks PlainBill....Leave a comment:
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Re: Powersupply proble, SAMSUNG LA32R71B
Thanks for the reply.
Here is the working link:
380V seems because this is a boost converter, based on the schematic, am I right? I here the main voltage is 240VAC 50Hz.Leave a comment:
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Powersupply proble, SAMSUNG LA32R71B
Hi all, I am now fixing a LCD TV, SAMSUNG LA32R71B. The problem is the PSU does not output right voltage level. PSN model is BN96-03775A, here is the schematics:
[url]http://www.elektroda.pl/rtvforum/download.php?id=365727&sid=09c77c7b28ddcb8edb7bacedd1274c26[/url]
I have done some checks and found stand by voltage is good but +24V and +12V are only +16V and +7.5V with no load (disconnected from the logic board), even worse when load was added(drop to around 9V and 4V). Apparently this is not right. Checked all the smoothing caps, they are all fine. Checked the...
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