BN44-00195A strikes back!

[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!

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

[steven10]

Re: BN44-00195A strikes back!

Don't you think 19V is to high as VCC?

And Why i'm getting an output of 20V when power is ON and 0.00V when power is OFF if the PFC circuit isn't working(always 350V on the big Cap both whit power ON/OFF)?

350V seems to much too, becouse the voltage between the legs of the big cap should be around 320V when power is OFF and than 380V when power is ON...

[budm]

Re: BN44-00195A strikes back!

Don't you think 19V is to high as VCC?

And Why i'm getting an output of 20V when power is ON and 0.00V when power is OFF if the PFC circuit isn't working(always 350V on the big Cap both whit power ON/OFF)?

350V seems to much too, becouse the voltage between the legs of the big cap should be around 320V when power is OFF and than 380V when power is ON...

Vcc of 19V is not too high.
When PS-on is present, it turned on the switched transistor to supply the VCC to the PFC IC and also supplies the VCC to run the 24V power supply, so right now the 24V power supply is running off the 350VDC in stead of close to 400VDC.

[steven10]

Re: BN44-00195A strikes back!

OK,I was expecting the VCC to be around 16V.

But i'm reading 2.45V between GND and INV pin of the PFC IC(The FAN7530 doesn't work if there's less than 0.45V on the INV pin) so I don't know why it's not working.

[budm]

Re: BN44-00195A strikes back!

OK,I was expecting the VCC to be around 16V.

But i'm reading 2.45V between GND and INV pin of the PFC IC(The FAN7530 doesn't work if there's less than 0.45V on the INV pin) so I don't know why it's not working.

Unless the Zener diode used in the Transistor linear regulator is not 15V. FAN7530 is internal 22V ZENER at VCC pin.
Read post 45 and later, did you replace the Zener?

[steven10]

Re: BN44-00195A strikes back!

Yes, I did that but I replaced the zener ones again and took some measurements.

PFC IC FAN7530

Pin1=~2.10V
Pin2=0.06V
Pin3=0.02V
Pin4=0V
Pin5=~0.2V
Pin6=GND
Pin7=0V
Pin8=17V

Big cap = ~390V both with power ON and OFF.

That's pretty strange cos the PFC circuit is not working at all but I have 390V(fluctuating) on the big cap.

Only the VCC changes with power OFF(from 17V to 0V), all the other reading stay the same...

So maybe there's something wrong with the SMPS IC?
What does PC804s do?

[budm]

Re: BN44-00195A strikes back!

It has to be working because you are getting 390VDC, if it is not working you will only get about 330VDC (230VAC * 1.414).

[steven10]

Re: BN44-00195A strikes back!

how it's supposed to be working with those readings?
Readings on pins 4 and 7, indicate that the mosfet is open

[steven10]

Re: BN44-00195A strikes back!

I'm also reading 0V on both windings of the LP801 transformer

[budm]

Re: BN44-00195A strikes back!

Pin 4 CS (current sense) will in mV high frequency AC KHz).
Pin 7 Drive will be high frequency AC KHz range.
If you remove the PFC POWER MOSFET then you will not have the 390V, so you see if the PFC is actually working or not.

[budm]

Re: BN44-00195A strikes back!

BTW: https://www.badcaps.net/forum/showpo...6&postcount=57
That Voltage should be enough to at least cause the backlights to flash on for seconds, so did you check and see if the Inverter board is OK and getting the BL-ON, DIM control signals from the logic board?

[steven10]

Re: BN44-00195A strikes back!

I didn't check the inverter board yet,I just took some measurements on the connector pins using chassis as ground, for now.

+24V(x5)=~21V
GND(x5)=0V
SOS=7.20V
ON/OFF=6.15V
A_DIM=3.10V
EX_PWM=3.80V

Backlights remain always off,but i've noticed that I can see images if I put a torch against the screen

[steven10]

Re: BN44-00195A strikes back!

the logic board is definetly good.
I'm also able to navigate trough the menu...brightness was set to 100, so I tought reducing the brightness could at least cause the bulbs to flash, but I was wrong

[budm]

Re: BN44-00195A strikes back!

I didn't check the inverter board yet,I just took some measurements on the connector pins using chassis as ground, for now.

+24V(x5)=~21V
GND(x5)=0V
SOS=7.20V
ON/OFF=6.15V
A_DIM=3.10V
EX_PWM=3.80V

Backlights remain always off,but i've noticed that I can see images if I put a torch against the screen

I do not know what the SOS pin is, may be some kind of error output pin.
The ON/OFF is there but are you sure it is that high?
Post good clear picture of the inverter board next.

[steven10]

Re: BN44-00195A strikes back!

I removed the power mosfet and still got ~390v,so
I replaced the DMM battery with a brand new one, and now my readings look much more accurate...
I'm actually getting ~300V on the big cap and ~15V on the 24V line.
The ON/OFF shows 5.19V now.
The PFC isn't working so I guess the IC is bad.
I'm going to replace this, ones again,but what I would to know is if there's any way to force the PFC to work,without the IC.

[budm]

Re: BN44-00195A strikes back!

If your line Voltage is 230VAC, then the Voltage on the cap should be = 230V * 1.414 = 325VDC (without PFC). so if you are getting 300vdc on the cap, then your AC must be <230VAC or your meter is still not in calibration.

[Galandil]

Re: BN44-00195A strikes back!

Hello guys, I'm back to the forum since the other 245B that I have at home went dead, usual problems due to the BN44-00195A power board.

I know already all the pieces I need to change, except one: the CY803S lenticolar cap.

I can't remove all the glue that's on it, so the only thing I can read is the value and tolerance: 471K, so it's a 470pF with +/-10% tolerance. What I'm missing is the voltage rating.

I tried to find the schematics of the power board, and one I found shows a completely different value for that cap: 102M 400V (so a 1nF +/-20% 400V). How is this possible?

Moreover, I can't find at the moment a CM812 (12nF 630V) with 3% tolerance, I could buy however one with a 5% tolerance: is it ok?

Any help will be very appreciated, and thanks in advance!

[eccerr0r]

Re: BN44-00195A strikes back!

Without knowing the exact usage of the particular devices, it's hard to tell, photos of the board with the suspect components (and their corresponding schematic) would be helpful.

However usually these low value caps are ceramic and last quite a long time, what makes you think these components are bad?

[budm]

Re: BN44-00195A strikes back!

CY803S is the Y type cap, that cap is use to reduce the EMI to make it pass the EMI test, it is not needed to function. When it is bad it will show leakage resistance. I have never seen this one go bad yet.

CM812 (12nF 630V) with 3% tolerance: that one is 5% (J) not 3%, the important thing about this cap is that it has to be Polypropylene type due to where it is used in the circuit, this one is the command failure that cause low or no 24VDC at the output on the cold side.

Bad glues: https://www.badcaps.net/forum/showth...ight=bad+glues

Pictures provided by shopjimmy.