BN44-00195A strikes back!

[budm]

Re: BN44-00195A strikes back!

"Just a not-so-important question: for some reason, now the blue standby led of the monitor is a lot dimmer than before" That LED runs off the either 5V or 3.3V drive circuits, so as long as your power supply is putting out the correct Voltages, then you will have to look at the LED driver circuits to see why it is dim by checking the DCV feeding the main board.

"Namely, the fusible resistor with a tolerance of 10%, the 12nF cap @800V instead of 630V, and the 47pf and 2.2nF ceramic caps @2kV instead of 1kV." no affect.

[steven10]

Re: BN44-00195A strikes back!

Hi, I had the same problem, while using my pc i heard a pop...
black screen and solid blue led...

I found that the 0.22 ohm fuse resistor was blown and the
two mosfets are shorted(FQPF9N50C).
I removed these components and then found that two pins of the TM802(EE1312?) are no longer shorted, compared to the identical ones in the opposite side.
all the other components seems to be fine.
is this normal? should i replace this transfomer?
Thank you all in advance.

[steven10]

Re: BN44-00195A strikes back!

does anyone know where I can get a tm802 transformer or an equivalent one?

[vinceroger69]

Re: BN44-00195A strikes back!

are you sure the transformer is bad? its not very often you see these fail maybe replace the three parts you have found faulty and retest the set.

[selldoor]

Re: BN44-00195A strikes back!

^ ^^ ^ +1 ^^^

Yes, If it is still on the board check for glue and remove it.
Corrosive and conductive glue is a killer on these

[steven10]

Re: BN44-00195A strikes back!

i replaced the parts(the 2 mosfets and the 0.22 ohm resistor) but now, I do have a short on pins 1 and 3 of the QM803 mosfet.
any suggestion?

ps: I had already removed all the glue.

[vinceroger69]

Re: BN44-00195A strikes back!

Maybe budm will will have a look at this thread and have a idea what to check now

[steven10]

Re: BN44-00195A strikes back!

I think that DZM805 and DZM806 are gone too
Tomorrow I will remove them from the board, hoping these zeners were the problem...

https://cdn.badcaps-static.com/pdfs/...f8a620fd8c.pdf

[TechGeek]

Re: BN44-00195A strikes back!

It has to be fusible flame proof type and correct Wattage due to safety requirement. You do want the monitor to catch fire when there is problem.

WHHHHHHHHAAAAAAAAAT!!!!!!!!

[budm]

Re: BN44-00195A strikes back!

WHHHHHHHHAAAAAAAAAT!!!!!!!!

My big typo!

[budm]

Re: BN44-00195A strikes back!

'I do have a short on pins 1 and 3 of the QM803 mosfet.'
QM802, 803 will show very low resistance between Gate and Source pin due to the coupling transformer drive setup, you are seeing the low resistance of the transformer windings.
BN44-00192 diagram will give you some idea as to how the QM802, 803 is driven.
If the Source and Drain are not showing as very low resistance the MOSFET are OK.
What happen most of the time is that the blue snubber caps shorted out and caused the fusible resistor to blow.

[steven10]

Re: BN44-00195A strikes back!

QM802, 803 will show very low resistance between Gate and Source pin due to the coupling transformer drive setup, you are seeing the low resistance of the transformer windings.

I do have very low resistance between Gate and Surce on the QM803, but I do have an open circuit between Gate ans Source on the QM802(broken transformer winding)

Any idea where I can get this transformer?

Thanks for the help!

[vinceroger69]

Re: BN44-00195A strikes back!

http://xppower.en.made-in-china.com/...T-EE1312-.html

[steven10]

Re: BN44-00195A strikes back!

I found out this post in another thread:

Hello, this forum has helped me a lot in debugging.

I also have a BN44-00195A PSU in my Samsung Syncmaster 245B.
For me, however, the error was another.
For me, the transformer TM802 has been destroyed by the bad glue. Thus, the FETs QM801, QM802 and resistance RM801 have been destroyed.
As a replacement for the FETs I used the type IRF840A.
And to replace the transmitter TM802 I used by Würth Elektronik the transformer 749196301. It must always be connected in series two coils. This one again has 3 coils. It has to be absolutely paid attention to the correct polarity (points in the diagram).
For the resistor RM801 I took a normal 0.22 Ohm and 0.6 watts.

The monitor is now working properly again.

Translated with Google Translator German to English.

I actually don't understand how this 749196301 should be connected. do you?
or maybe is there an equivalent that fits better on the board?

http://xppower.en.made-in-china.com/...T-EE1312-.html

thanks for the link but maybe this 749196301 or an equivalent, should be easier to get

[steven10]

Re: BN44-00195A strikes back!

I repaired the bad transformer!
It has a broken winding(it broke very close to his terminal),so just a bit of work with my soldering iron and problem solved

Unfortunately my monitor still show anything on the screen

What i've done so far:
Replace QM801 and QM802(mosfets)
Replace RM801 (0,22ohm fuse resistor).
Repaire TM802 (transmitter).

I don't know what else I can check,
Any suggestion?

[budm]

Re: BN44-00195A strikes back!

Do you get 24VDC now?

[steven10]

Re: BN44-00195A strikes back!

Do you get 24VDC now?

No, still 0.00V...

[steven10]

Re: BN44-00195A strikes back!

Tested some more components and they seems to be fine:
RB801 and RB802 (100k) both 100.8k
CM812 (12nf 630V) 10.8nf
CM806 (47uf 1kV) 42uf

I measured the voltage between the legs of the big capacitor and i've got a reading of 305V-310V both with power on and off...
I read something about this cap and it should be around 370V when power is on and about 170V when power is off.
Don't know why I'm getting 310V in both ways though

[budm]

Re: BN44-00195A strikes back!

You need to have PFC Voltage boosted Voltage for the 12V/24V power supply to run.
This one may be on its way out 'CM812 (12nf 630V) 10.8n'

You need to check the PFC diode and also verify that the PFC IC has VCC Voltage to run.

[steven10]

Re: BN44-00195A strikes back!

Diodes(DP801 and DP802) are fine they both show a drop of ~ .500.

I'm able to read 11.8V between pin 8 and 6 of the PFC IC,when power is on and 9.8V when power is off.

What's the next step?
by the way, thanks for the help