Cross reference for B90N08

[ned1]

Working in Hanns.g monitor HL273 with bad power supply. It appears to have short B90N08 diode. Can someone cross reference the diode since I can't find it to purchase.
Thanks

[dick_barton]

Re: Cross reference for B90N08

It appears to have short B90N08 diode.

Are you sure it's a diode. Can you post a picture?

[budm]

Re: Cross reference for B90N08

The main fuse also blown? And yes, pictures of what you are working on.

[ned1]

Re: Cross reference for B90N08

I removed diode from board and all 3 leads are short to each other. The main fuse is not blown, all capacitors are ok. During lead lifting I damaged diode so I will need it anyway. I will post pictures shortly.

[ned1]

Re: Cross reference for B90N08

Here is the picture

[ned1]

Re: Cross reference for B90N08

I put the diode back for reference of placement on board. You can see damage from removal.

[CapLeaker]

Re: Cross reference for B90N08

A 90N08 should be something like a 90A, 80V Mosfet. However, IF that is shorted, then the fuse should be blown and maybe a few more parts yet, as budm already suggested. Pictures would be nice indeed.

Never mind me on the pictures....

[CapLeaker]

Re: Cross reference for B90N08

Yeah... I can see it. Q2 you are talking about. That's a Mosfet. Trick is to preheat that board first, or having a sodering iron with some "Ooomph".

[dick_barton]

Re: Cross reference for B90N08

You could have removed it by applying plenty of fresh solder on the tab and keeping your soldering iron on it until you can lift it up with tweezers or small nose pliers.

[dick_barton]

Re: Cross reference for B90N08

Digikey have some similar logic gate level mosfets eg FDD3570-ND which may be a suitable replacement.

[budm]

Re: Cross reference for B90N08

BTW, that power MOSFET is for the Boost converter circuit to step up the Voltage for the LED Backlights.

[ned1]

Re: Cross reference for B90N08

Thanks

[ned1]

Re: Cross reference for B90N08

So should I follow dick Barton recommendation or I need different one?

[dick_barton]

Re: Cross reference for B90N08

If that mosfet was short circuit then it may also have damaged U1. I would also check the resistors around U1 are all still the correct value and not damaged.

Edit
What is the part number written on U1

[CapLeaker]

Re: Cross reference for B90N08

matter effect, you would have to check the whole gate drive circuit.

[ned1]

Re: Cross reference for B90N08

The marking on U1 Is OB3362HP

[ned1]

Re: Cross reference for B90N08

Received FDD3570-ND and installed. Getting green light on the monitor power button indicator, but still no picture. Any more suggestions.

[flocko]

Re: Cross reference for B90N08

I would think the OB3362 four string LED driver IC could also be blown, always best to replaced as a pair with mosfet, and check current limiting resistors as Dick suggests

[dick_barton]

Re: Cross reference for B90N08

Received FDD3570-ND and installed. Getting green light on the monitor power button indicator, but still no picture. Any more suggestions.

What voltages are now missing????

[ned1]

Re: Cross reference for B90N08

with board removed and plugged to 120V I am getting 5V to both 5V pins to ground in and no voltages on ENA or ADJ pins to ground.