32 samsung lcd will not turn on just blinks 5 times

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

i did not saw your post #59 before i sent #60

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

That diode has low Vf rating, that is why it show low reading in the forward reading.
If you plug the TV into the outlet, make sure the cn802 is not connected, this should happen, the voltage on the large cap should jump up to 400v and stay there, then the backlights should come on and stay on. Is that what is going on?
If you are getting 290vdc on the cap, it means that your AC is just a little above 200VAC.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

i took out the mosfet to measure pin7 on the PFC again but i still got 8.5 kOhm. I tested RP806 off board = 10kOhm. the reading between the point of RP806 tested OL.

Then i resolder the RP806 back in place and did the readings on RP806 and it was back at 8.5kOhm. All these tested with Mosfet off board.

So TV plugged in outlet with CN802 NOT connected. I got 1sec blacklight. I measure voltage on the cap while i did this again.

i got 400v when plugged in but immediatly it drops to 290V. All this without connecting CN802

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

now i have the mosfet QP802S out, how do i test this. I do not have any Ohm readings. but if i put it to diode-mode, everything reads OL except for Black on pin2 and red on pin3, i got 470

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

ok the real reading of CN802 as you asked me.

PIN//STBY//PW-ON
1 = 0.03 // 1.13
2 = 5.19 // 5.19
3 = 0 // 0
4 = 13.04 // 13.02
5 = 0 // 0
6 = 0 // 0
7 = 5.19 // 5.18
8 = 5.19 // 5.18
9 = 0 // 0
10 = 13.04 // 13.02
11 = 13.04 // 13.02
12 = 0.03 // 5.14
13 = 0.08 // 2.19
14 = 0.03 // 0.16
15 = 0 // 0
16 = 0 // 0

an other update : when plug in without the mainboard i got a 1sec backlight. But with the mainboard connected i don't get this 1sec backlight at all.

i also see that the TV turns on (blinking 5 times) from the moment i plugged it in.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

Hi budm,

I still haven't given up yet. I want to know how this pfc circuit works, do you know where i can find explanation for dummies ? lol

One more thing to be sure. If this RP823 is out and the TV is working normally, does that mean that ONLY the PFC circuit is faulty, or can there be other faulty circuits ?

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

With RP823 removed and the TV will function does not quite make sense to me yet since the B+ on the cap will not be at 400V like it should be since the PFC is not running. Can you tell what the DC voltage on the big cap is when the TV is running without PFC IC being powered.
Second thing that does not make sense to me is that when you hook up the RP823 back in, even though the IC still does not function (no output drive for the Gate), which means the TV should also work since the PFC is still not functioning, this symptom does not make sense to me since both conditions are the same, no PFC functioning.
I must be over looking something.
So can you see what DC you have on that big cap with the RP823 removed? All we want is to have 400VDC on that cap.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

With RP823 out, i got 290V on the big cap and TV is working

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

Boy, your AC voltage in Laos must be pretty bad and not normally at 220VAC, otherwise it have about 311VDC (220 x 1.414 = 311) on the that cap.
It is strange that the TV is still functioning OK but I can see why when you line voltage goes down to 160V the TV stops functioning.
I am still trying to figure out what else you can check to see why the PFC is not working.
Let me look at the circuits some more.

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

DP805 31GF6L: By the way, which Diode this TV has? per you post: http://dc195.4shared.com/doc/C_niqLZi/preview.html
Is it 31GF6L-5705 like it should be per bulletin?

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

Risk Range :
0907*/0908*/0909* marked on diode

mine is 31GF6 - 0931G

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

hi budm,

do you still follow up ? if yes, what can i do more in this case ? if you need some more readings on how or what, please tell me.

Thanks in advance

[craigc15]

Re: 32 samsung lcd will not turn on just blinks 5 times

This problem is very likely caused by a defective diode in the PFC circuit (DP805). Apparently there is a service bulletin for this problem. I just fixed a TV with this problem and when I tested the diode out of circuit, it tested fine in diode check mode and resistance mode (in both directions).
The defective diode causes a "UVLO" failure in the backlight circuit because the voltage across the main cap is not as high as it's supposed to be. I'm now getting around 340V with 120V line, but with the bad diode I was only getting around 320V.

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

I believe 340V is still too low, most PFC/Voltage booster will bost the voltage to around 380 ~400V range.

[Beowulf]

Re: 32 samsung lcd will not turn on just blinks 5 times

Hi,
I got a LN32C540F2DXZA that uses the same power supply (BN44-00338B) as the original poster indicated. The tv has a cracked screen though but I want to fix it to gain experience and also sell the parts or something.

What happens is I get the red stby led, but the tv won turn on.

I believe in my case the problem is with the power supply. Because:

#1 If I disconnect the motherboard and plug the ac, the tv still won turn on and light up the backlights, although you see them flash when you connect and disconnect the power plug, not all the time but most of the time.

#2, because if I connect the motherboard or any load the power supply will drop the output voltages.

#3 The output voltages I'm getting are rather weird, depending on whether I have or dont have boards connected.

Here are some voltage measurements I took:

Everything connected

CN802

1-Varies from below 0v up to 3.0v
2-varies below 0v
3-Varies from below 0v up to 3.0v
4-0v
5-Varies from below 0v up to 3.0v
6-varies around 0.5
7-gnd
8-0v
9-gnd
10-0v
11-Varies from 0 up to 0.4v
12-0v
13-Varies from 0 up to 0.4v
14-varies around 0.4
15-Varies from below 0v up to 3.0v
16-5.2v
17-Varies from below 0v up to 3.0v
18-0.013 then 0.7 (changes from one to the other within 5 seconds and continues this cicle)

CN803

1-varies from 0.5 down continuosly
2-
3-0
4-varies below 0v
5-gnd
6-gnd
7-gnd
8-gnd
9-gnd
10-varies from 4 down to 0.5 continuosly
11-varies from 4 down to 0.5 continuosly
12-varies from 4 down to 0.5 continuosly
13-varies from 4 down to 0.5 continuosly
14-varies from 4 down to 0.5 continuosly

With the motherboard disconnected

CN802

1-4.7
2-0.034
3-4.7
4-1.2
5-4.7
6-0.7
7-GND
8-0V
9-GND
10-GND
11-3.5
12-GND
13-3.5
14-3.5
15-4.7
16-5V
17-4.7
18-0.7

CN803

1-0.7V
2-says it's not connected but I'm getting 3.5v
3-1.2
4-0.9
5-
6-
7-
8-
9-
10-6V
11-6V
12-6V
13-6V
14-6V

ALL BOARDS DISCONNECTED

CN802

1-14.9
2-
3-14.9
4-
5-14.9
6-
7-GND
8-
9-GND
10-
11-5.2
12-
13-5.2
14-5.2
15-14.9
16-5.2
17-14.9
18-0.7


CN803

1-0V
2-0V
3-0V
4-1.2
5-GND
6-GND
7-GND
8-GND
9-GND
10-29V
11-29V
12-29V
13-29V
14-29V

[dday2222]

Re: 32 samsung lcd will not turn on just blinks 5 times

Im having the same issue.
My samsung LN40C630K1FZA tv wont trun on. The past couple weeks the redlight would blink and the tv would turn off. Just last night i tried turning it back on and it wont start up. The redlight blinks a couple times then goes away. I can press other buttons on the TV and the red light reacts to the button pressing. I do not hear any clicks and I doubled checked to see if any of my capacitors have busted, which they havent.

Please help

[dday2222]

Re: 32 samsung lcd will not turn on just blinks 5 times

I also unplugged the main board from the other ones and my tv will light up. What could be the problem?

[dday2222]

Re: 32 samsung lcd will not turn on just blinks 5 times

im having the same issue.
My samsung ln40c630k1fza tv wont trun on. The past couple weeks the redlight would blink and the tv would turn off. Just last night i tried turning it back on and it wont start up. The redlight blinks a couple times then goes away. I can press other buttons on the tv and the red light reacts to the button pressing. I do not hear any clicks and i doubled checked to see if any of my capacitors have busted, which they havent.

Please help

ln40c630k1fzxa

[robin94539]

Re: 32 samsung lcd will not turn on just blinks 5 times

Hi Budm and Beowulf,

I have the same exact TV(Samsung LN32C540F2DXZA) and the same exact symptom as posted by Beowulf(see post #75). After searching the internet and checking with a digital multimeter, I think something wrong with the power board(BN44-00338B). The readings of the multimeter are very similar to that posted by Beowulf:

1. When disconnecting all the cables, power board readings are:
CN802--pin1/3/5/15/17(B13V): 4.2v
CN802--pin11/13(B5V): 2.13v
CN802--pin16(A5V): 5.2v
CN803--pin10~14(24.5V): 8.7v

2. When all the cables are connected:
CN802--pin1/3/5/15/17(B13V): continuous change from 0 to 2.9v
CN803--pin10~14(24.5V): continuous change from 0 to 3.9v

Since
1) A5V voltage is ok;
2) the main cap(100uf, 450v) reading was 100uf when I measured it (on board);
3) the PFC_OUT voltage reading is 377v(half sine wave);
4) B13V reading is 1/3 of its normal value;
5) 24.5V Inverter reading is 1/3 of its normal value;
6) no obvious physical damage(cap popup etc) on the power board and main board.

I guess one or more of the following components might be bad:
1) ControlIC ICM801, I see someone selling the IC on ebay;
2) High power cap "CM808", I also see someone selling it on ebay;

Could Budm and Beowulf please tell me what should I do next? Thanks a lot!

[beano]

Re: 32 samsung lcd will not turn on just blinks 5 times

I had the same thing on a Samsung 40inch replaced main pwb works great