bn44-00338b

[still4given]

Re: bn44-00338b

You're right, I didn't notice that.

How is this circuit supposed to work? Obviously 23mv won't turn on the MOSFET but what happens when the MOSFET turns on? Looks like it will force positive voltage onto the ground? You can see I don't understand how an SMPS works.

So you still think the IC is the problem? I ordered some but likely won't see them for a week or so, coming from Hong Kong.

[budm]

Re: bn44-00338b

Here is the application notes for the FAN7530, the example circuit is about the same as used in the board.

[still4given]

Re: bn44-00338b

Hi Bud,

I hope you are still monitoring this thread. My replacement IC finally arrived so I installed it. That wasn't the problem. I still have exactly the same voltages I show in post #17. For some reason the IC is not turning on. I have read through the docs for the IC and though I understand it a little better, I'm not sure what to look for as to why it is not turning on. Any other things you can suggest to look for?

Thanks, Terry

[budm]

Re: bn44-00338b

OK, so what DC Voltage do you get compared to the one in post 17?

[still4given]

Re: bn44-00338b

Exactly the same, everywhere. I bought more than one IC so I even swapped in a second one. No change. The docs say the IC compares the inverted and the non-inverted inputs. I'll assume the inverted in the INV pin but I don't know which pin is the non-inverted. Something is not sending the correct voltage or current to make the IC happy. Have you had the chance to mark down the correct voltages for each pin on the IC? That would be very helpful.

Blessings, Terry

[still4given]

Re: bn44-00338b

I'm attaching another partial of the schematic with the voltages to hopefully give a better picture of what's going on.

Thanks, Terry

[budm]

Re: bn44-00338b

Can I see the bottom side of the board around the MOSFET and the IC you replaced?
DP803 Diode (Gate discharge diode) is connected in parallel with low Ohms resistor so it will show conduction on both directions.
Something is locking out the IC from generating the output signal to drive the MOSFET.

[still4given]

Re: bn44-00338b

Here you go.

Edit; adding a shot of the bottom where I replaced the FSR

[still4given]

Re: bn44-00338b

Hi Bud,

I'm still hoping to fix this with some help. I hope you can find the time to take a look at my findings and make some more suggestions. I could just buy a replacement but then I won't learn anything.

Blessings, Terry

[budm]

Re: bn44-00338b

I have to do more thinking on this one.

[still4given]

Re: bn44-00338b

I appreciate that. Standing by.

Thanks

[still4given]

Re: bn44-00338b

Hi Bud,

Any more suggestions as to what I might check to help get to the bottom of this issue?

Thanks, Terry

[Alastair E]

Re: bn44-00338b

Tried a new MOSFET...?

[saularciga]

Re: bn44-00338b

Hola, el problema que tienes esta en la linea que sale desde el diodo DP802, atraviesa BP803 y BP804 y continua por RP813, RP814,RP815,RP816, RP817,RP818 y RP819.
Mide estas resistencias, lo mas probable es que una de ellas esta abierta.
Cualquier variación fuerte de voltaje en la linea de entrada ( 120vca) provocara en daño del circuito o el daño de estos componentes.
Apagada la fuente o en standby , debes tener 180vcd aproximadamente 180VCD en BP803, con la fuente trabajando al 100% debes tener 380 - 400vcd

[saularciga]

Re: bn44-00338b

See notes en datasheet in page 3:
The OVP comparator shuts
down the output drive block when the voltage of the INV pin
is higher than 2.675V and there is 0.175V hysteresis. The
disable comparator disables the operation of the FAN7530
when the voltage of the inverting input is lower than 0.45V
and there is 100mV hysteresis

[still4given]

Re: bn44-00338b

Tried a new MOSFET...?

No, I have not tried that. Do the voltages indicate it is faulty?

See notes en datasheet in page 3:
The OVP comparator shuts
down the output drive block when the voltage of the INV pin
is higher than 2.675V and there is 0.175V hysteresis. The
disable comparator disables the operation of the FAN7530
when the voltage of the inverting input is lower than 0.45V
and there is 100mV hysteresis

I don't quite follow you. INV pin is 1.1V which is higher than 0.45V and lower than 2.675V. I don't understand the term hysteresis nor how to check for that.

Thanks, Terry

[still4given]

Re: bn44-00338b

I ordered a new mosfet. I get back to you once I've replaced it.

[still4given]

Re: bn44-00338b

Hi Guys,

I installed a new MOSFET and have no change. Do any of you have a suggestion for where to look next?

Thanks, Terry

[budm]

Re: bn44-00338b

Nothing from me at this point yet.

[still4given]

Re: bn44-00338b

I'd love to see a schematic with some voltage readings of other pertinent areas. If someone has one of these that they could take some readings one it would be most helpful.

Thanks, Terry