Samsung 24" power supply BN44-00195A first stage voltage?

[gsmtechno]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

But did you check the capacitance of that blue rectangular cap that I ask you to test?
That is the common failure cap in the 24V power supply section.
BTW, PS-ON has to be present to turn on the 24V power supply section, you do have that command signal, right?

I replaced the cm812, ps-on present. i also replace all CAP.

[budm]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

Next then will have to find out if you get the VCC to SMPS IC for that 24V power supply section.

[Yannick99]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

I know it's an old thread... but still, need help. I have a BN44-00195A fixed couple years ago and now new problem. QM801, 802 blown with the 0,22ohm rm801. Also a 100 ohm to the gate of qp801(not in schematic). Replace those parts. Turn on with bulb in serie and this one was turn on.... I tell to myself, i'll try direct. And was working again. 385vdc on big cap, 24v, 5v all was looking fine.

Reinstall the monitor all was ok and 5 minutes later it wasn't working again. Same mosfet, fuse blown.

What can be the issue ?

[R_J]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

So both mosfets QM801 & QM802 blew again? what about QP801? why was the gate resistor bad? What was the marking on the resistor? It is unlikey it went on its own without QP801, RP819 and ICP801s being bad.
What is the voltage on the large cap now? and do you still have +5v standby?

[Yannick99]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

So both mosfets QM801 & QM802 blew again? what about QP801? why was the gate resistor bad? What was the marking on the resistor? It is unlikey it went on its own without QP801, RP819 and ICP801s being bad.
What is the voltage on the large cap now? and do you still have +5v standby?

Yes both. QP801 is fine, and the 100 ohm on his gate is was. I dont know why this one blew on first time.

Now fuse are blew and mosfet are shorted. Must replace that again.

For the fuse i maybe did an error. It was 100 marking. I put 100 ohm but 100 ohm is 1000 marking. I do not have the priginal resistor but found a picture on internet. I did a red circle.


https://1drv.ms/u/s!AnKLPDy3pII_vkbe...7DfEy?e=5gE13g

But a gate have no current so 100 ohm instead 10 dont think it's my main problem.

Also, my bulb was turned on. Meaning the power supply itself take current without load. I dont know if this is normal ? Without bulb (direct) i had my 385vdc, 24v, 5v like normal.

[R_J]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

If the resistor is marked 100 it is 10Ω NOT 100Ω DP803 zener could be bad

[Yannick99]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

If the resistor is marked 100 it is 10Ω NOT 100Ω DP803 zener could be bad

Yes, my mistake. I'll check on tomorrow for the zener. Let you know thank you

[Yannick99]

Re: Samsung 24" power supply BN44-00195A first stage voltage?

If the resistor is marked 100 it is 10Ω NOT 100Ω DP803 zener could be bad

Replaced resistor, check zener = ok.
I installed 2 other mosfet. I used irfp460 (to247) just for testing i do not have any 9N50C with me.

Now, with no load i pull .1 amp on 120vac.
5.2v standby = ok
385vdc on cp803 = ok
24v output = 22.3vdc i had 24v with 9N50C and i dont have any reason to not have 24vdc again. With no load i dont think that the different mosfet is a problem.
Also, at the gate of the mosfet i have 50% of duty cycle. It's huge without any load.

At the output of large transformer. Just before the 2 diode. I have 90vdc peak to peak 50% duty cycle. And the other side of diode it's rectified to like i said 22,3vdc.

Is possible that transformer itself is short somewhere. The output ohm like 0,2ohm and if i short my probe i read 0,2ohm so... looks short to me! But if this was shorted, i couldn't have 90vdc peak peak... i dont know