Re: Samsung Syncmaster 245b BN44-00195A
RP819, the 5W resistor on QP801S source mesures 0.21 ohm. Has 0.15ohm declared on it and is marked as RP814S on the board.
The diode DP803 was 0.2V both ways in the circuit so I desoldered it and it tested 0.5V ok, so good. But DP803 on the board is connected to pin 7 of ICP801S. If you are referring to the DP803 on the schematic, between pin4 of ICP801S and ground, I can't find it. There is the SMD capacitor CP806 there, but I dont' see the diode.
The PFC are P-marked components arround ICP801S?
Should I keep the...
Mandor
Member
Last Activity: 07-26-2021, 11:51 AM
Joined: 08-02-2020
Location: Zagrebacka
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Re: Samsung Syncmaster 245b BN44-00195A
J808 is next to icb801s. Disconnecting it raises vcc on icp801s to 15v.
I desoldered the pin 15 of icm801 and no change. Main cap at 315v.
I have desoldered all the optocouplers before and tested with multimeters ok.
Zenner arround which ic? Zdb801 is 14.9v across terminals when ps on.
Qb801 Bce 15.5, 17, 15v.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
CP801S is always 310-315V. No change on power on.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
18.3V on collector. 0 on base and emitter on standby.
Rb808 measures 2.1 ohm in circuit. Colors say 2ohm....Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
No, that's just some glow from the lamp. Continuity is good on that transformer pin and the trace from optocoupler going arround it.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
You are very clever. The resistor 44ohm was open. I replaced it with 43ohm, and now we're back. It wold have taken me ages to find the resistor fault. Have the S_B 5V. No voltage on +5 to the control board
The QB801S (QB802S on the schematic i guess) is B,C,E= 11V, 12V, 10.5V.
10.8 on ICP801S....Last edited by Mandor; 04-07-2021, 12:45 PM.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I don't know where to find the correct schematic. I think the one in this thread is slightly different as I said and you said before. Left what I was referring to is lower left on my latest picture posted, the control board connector side.
i'm sorry if I seem dumb, that is because I am. It's the first time I tried something like this. I never had to troubleshoot anything near this complex. School projects of 10 components 20 years ago is my experience.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
Removed the cap.
The S_B is not working. Whole connector is now showing signal on attached picture.
The board is BN44-00195A.
Looks like I burned something on the left side....Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
Hello. I have been abroad for a few months. Sorry.
I'm am back at it. I really want to learn something from this.
I hooked up an osciloscope and point 3 on the pic showed slightly oscilating ~10V. You keep mentioning CB806 and it was not populated on my board. I did buy this monitor used but I don't think anyone was opening it. So i put on 47uF/50V at point 2. The osiloscope pic is from point 2 with the cap in. The voltage is oscilating sawtooth slowly. 2 second period. Looked a bit strange to me, so i took a pic....Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
So I'm looking at datasheet for TDA4863 and it says VCC should be Vz 18-22V. It's called zenner voltage. Great. So i try to find a zenner diode in the circuit diagram. There it is right above the chip. DZP801, part number BZX84C18 and it should be 18V according to datasheet. So i thought i'd check that.
But I have two diodes on the actual board. DZP801 and DZP802 and they are P6KE300A and have 140V and 210V on them.
OK DZP801 kathode should be on pin 7 of the IC. I can only see gate of QP801S via resistor.
I'm just lost and...Last edited by Mandor; 10-17-2020, 04:47 AM.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I also put in a new pair of correct mosfets. ICM801 and ICP801s still have 10.4VLeave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
Replaced all the electrolytic ones except the biggest one.
Nothing changed....Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I took most of the electrolytic caps out and measured them and they all seemed fine on capacity test. Should i test in another way?...Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
ICM801 is MC33670P.
Positive side of CP804 is 10.43V relative to negative lead of big high-voltge cap. cap. It connects to VCC of ICP801S (pin 8) vis J806. ICM801 is on the other side of the board. ICM801 on it's VCC (pin 15) also has 10.39V. So i guess they are connected.
I think the jumper you are refering to is J816 on my board, not JB816.
I do have IRF840 insted original mosfets. The new 9N50C parts did arrive from Mouser but I don't know If I waant to risk blowing them yet.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I still don't know what to do.Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I disconnected the cable.
Put a little switch between S_B and PSON.
CB806 is missing, like it was never installed. I measure 266Vdc between the pads when switch is OFF and 310 when switch is ON.
CP811 I can't find. I guess the ICP801S is the SMD part on the back. If I measure PIN8 of SMD dip to the ground (minus on graetz), switch OFF reads 0Vdc and ON reads 10Vdc....Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I think my board is a little bit different.
I Found the connector CN851 with fewer pins which has PSON and S_B. S_B has 5.23V.
The big electrolytic cap has 317V on it.
The only blue rectangular cap is CM812 12nJ630V measured out of circuit 12nF.
The new 0.22Ohm resistor measured in circuit 0.22 Ohm.
How do I go about verifying that PS_ON is present? PSON pin is 0.3V. I tried shorting S_B and PSON pins but big cap is stil 317V and not 380V and there is no voltage on 24V/5V pins.
[ATTACH]218036[/ATTACH]...Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
Isolation kit arrived along with the 0,22/2W resistors.
I put it all back together with IRF840 as replacements until i get original mosfets.
I'm back at the biggining now. The power button is illuminated but no picture or light on the LCD. Windows recognize the monitor correctly.
I tested the connector pins on the powerboard and i cant find any voltage between labeled gnd and 5.3V pins.
Any bright ideas? It's been a long time since i learned this stuff in highschool, sorry if I sound like an idiot. :-)Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
I ordered some isolation pads and nipples as they call them.
It was stupid to screw mosfets into heatsink without isolation.
What else could I check? Why would the resistor be blown? I read it as 0,22 Ohm. Should I check anything else before I turn the power back on?
In case it blows again even with all the goo cleaned up?...Leave a comment:
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Re: Samsung Syncmaster 245b BN44-00195A
So I took out my mosfets and they seem ok out of circuit. I can open and close them with a multimeter.
The replacement resistor blew.
The fuses are ok.
The element marked BM801 is shorted both ways. Not sure what it is.
I desoldered 3 diodes i suspected conduct, but they all tested ok out of circuit.
I thought one of optocouplers could be bad but tested ok out of circuit.
What should I take a look at? Desolder every component and test it?
At least help me with the best order. Also can IRF840 mosfet...Leave a comment:
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