BN44-00195A strikes back!

[budm]

Re: BN44-00195A strikes back!

So we can still cannot get the PFC IC to run some how.

[steven10]

Re: BN44-00195A strikes back!

I'm getting steady19V VCC (pin 8) and 0.00V on pin 7(pin out)

[budm]

Re: BN44-00195A strikes back!

I'm getting ~350V on the big cap both with power on and off

That is not right, the PFC Voltage should be activated when the PS-ON (ON/OFF) signal is received from the main/logic board. I do not think the PFC is running.
So are you getting the DCV between the VCC pin and GND of the PFC IC controller?

[steven10]

Re: BN44-00195A strikes back!

I'm getting ~350V on the big cap both with power on and off

[budm]

Re: BN44-00195A strikes back!

At least you have 20V or so feeding the inverter board, then the inverter board should try to light the lamp when the inverter board gets the BL-ON commnad signal.
BTW, what is the PFC boosted Voltage do you get now?

[steven10]

Re: BN44-00195A strikes back!

Shipping time takes to long, so I ended up going to a "local" store, 2 days and the parts were there

Parts replaced and still black screen but i'm now getting 20.5/22.7V(fluctuating) on the 24V line(before was 0.00V ).

Any suggestion?

PS: Reading taken with everything plugged in

[steven10]

Re: BN44-00195A strikes back!

Ok,tested the MOSFET with a 9 volt battery and it is good(probably my DMM doesn't have enought power to turn this MOSFET ON).

Put it back and read 0.67V on pin 7(PFC output pin).

Checking for low resistance readings on the IC, I got :

1)6K7
2)5K8
3)1M1
4)1R
5)5K8
6)GND
7)5K5
8)170R

Pins 1,3,4 and 6 seems good.
Pins 2,5,7 seems bad.

By removing the jumper that drives the VCC to the SMPS IC, I'm able to read correct 7K4 on pin 8 of the PFC iC, so pin 8 is good,but the SMPS IC is bad

I ordered a FAN7530M and a MC33067N,any chance changing these parts can return the monitor in a working condition?

[budm]

Re: BN44-00195A strikes back!

You can try another power MOSFET with the same rating.
Not much you can do for testing the IC, You can test the resistance readings between GND pin against all other pins to see if they show low resistance.

[steven10]

Re: BN44-00195A strikes back!

How can i test di PFC IC?
Can i put a working 600V 7A mosfet just to check if I'll get the boosted voltage?

[budm]

Re: BN44-00195A strikes back!

So now you do have 16V for PFC IC VCC but still no boosted Voltage, so it can be bad IC or Bad MOSFET, but 99% the bad MOSFEt will fail in shorted out mode.

[steven10]

Re: BN44-00195A strikes back!

I've pulled off QP801s and it seems bad.

The source-drain diode is fine but I'm not able to turn it on the "On state"...
When I charge the gate capacitance, I got no readings between drain and source(open circuit).

Before pulling off QP801s I was getting 15.9V on the Vcc line, so the PFC IC was getting what it needs to run.
The 19.5V on the QB802 collector seems to be low and I don't know why the voltage getting higher when power is off.
maybe something related to the bad QP801s mosfet?

[steven10]

Re: BN44-00195A strikes back!

I replaced QB802 with a 2sd2394 60V 3A NPN transistor.
didn't found a 15V zener ,but I just replaced it with a 10v zener in series with a 5.1V one.

These were the reading BEFORE changing those parts:

Power ON/OFF:
A = 17.9V/15.7V
B = 11.7V/9.7V

These are the reading AFTER changing the parts:

Power ON/OFF
A = 19.5V/22.5V
B = 15.9V/0.0V

The voltage between the big cap almost remained the same,now it fluctuates from 310V to 325V(305V to 310V before) both with power ON and OFF

Still 0.01V on the 24V line.

[steven10]

Re: BN44-00195A strikes back!

Great so you need to get the 15V ZENER and the NPN TO-220 60V 2~3A rating.
Do you have any scrapped board for steling the parts from?

I found a 2sd2394 (TO-220F package)NPN 60V 3A transistor from a scrapped power supply board,it should be fine.
Tommorrow I'll check for zener,it's over midnight here

[budm]

Re: BN44-00195A strikes back!

The diagram is not exact match with the *-00195 board.

[steven10]

Re: BN44-00195A strikes back!

Of course I mean QB801(QB802 on the diagram) not QM801... my mistake

[budm]

Re: BN44-00195A strikes back!

Great so you need to get the 15V ZENER and the NPN TO-220 60V 2~3A rating.
Do you have any scrapped board for steling the parts from?

[steven10]

Re: BN44-00195A strikes back!

QM801 is bad!
I just removed it from the board and it has a short between B and E...

[steven10]

Re: BN44-00195A strikes back!

These are the readings:

17.9V between A and GND REF
11.7V between B and GND REF


While looking very close to the smd side of the board(thanks to your picture),i've noticed that DZB805 had a tiny little crack on top of the package,just a gentle touch with a sharp screwdriver caused the package to break.
Now there's a "huge" hole on this,i'm going to test it but i think it's 99% bad.
I also noticed that QM801 shows a very low resistance between Emitter and Base, don't know if this depends on the bad zener...

[budm]

Re: BN44-00195A strikes back!

OK, I found my old notes.
QB801 is for the 15V regulator circuit.
Check the DCV between A and GND REF, B and GND REF when power switch is activated.

[budm]

Re: BN44-00195A strikes back!

I expect the VCC to be around 15~18V range when it is running, 11.8 is pretty close to then minimum 11V, worst case is 12V requirement for start up.
If you look at the diagram of the BN44-00192, you will see the 15V linear regulator transistor QB802.