Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount diode.

[johnboy1313]

I picked this set up on New Year's Eve. I can't find the schematic for the PSU pat number 1AV4U20C33700. It's not in the service manual. I opened it up and found no standby voltage and a blown main fuse on the PSU. Upon closer examination, Q808 (a W25NM60N MOSFET) is shorted. I was testing for shorted surface mount components and thought I found two shorted diodes at D805 and D810. They are both very close to Q808. I pulled D805 off and proceeded to lose it off the end of the tweezers. Oh well, it happens. Before I lost it, I tested it out of circuit and found that it was good. I looked through some parts boards that I have and found one with a 20N60C3 MOSFET that seems like it will work for testing. On the parts board, I also found a small diode labeled A2 installed in a similar position to the one I lost off of the other board. I scavenged it as well.

With the scavenged parts installed in the Sanyo PSU, the fuse doesn't blow when plugged in. There is 160V at the main cap, and I have standby voltage. When I press the power button, the power indicator lights for about 10-15 seconds and then goes out. The voltage at the main cap never changes from 160V. It seems that something in the PFC section of the PSU is still faulty. I'm not knowledgeable enough to know if the parts I installed are the issue, or if there is another failed component that I've missed.

Does anyone have a schematic for this power board?

Here are pics of the top of the board. The W25NM60N is out of circuit at this point and the board is burnt just under the main cap in the fourth picture below (IMG_5032).

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

Here are pics of the bottom of the board. You can see where the original MOSFET was located, Q808 in the upper right corner of the second picture below (IMG_5025). You can see D805 and D810 just above Q808 in that picture as well.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

Here are pics of the MOSFETs and the D805 and D810 diodes, along with data sheets for both MOSFETs.

The original MOSFET


The replacement
https://cdn.badcaps-static.com/pdfs/...f3d222ab2f.pdf

I'm really hoping that my issue is just ignorance and that one of the more knowledgeable members here can point out my mistakes. I really don't wanna drop $85 on a used power board.

Thanks in advance.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

The PSU will not force on either. I've checked all diodes in that area of the board as well.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

I see a lot of activity on here right now. How about some of you guys on the other side of the planet, any of you care to take a stab? Bud, you're on the west coast, you out there tonight?

[budm]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

When that power MOSFET for the PFC Voltage shorted out, it's more likely to take out the Gate drive out put of the PFC Controller IC with it plus the resistors and diode for the Gate drive circuit.
You should get the P/N's of those ICs to get the spec sheet and the pinout. I would not replace the MOSFET without the IC at the same time.

[tw2005]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

C825 ceramic. how many stabs do i get before I'm sacked from guessing?

[budm]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

"Q808 (a W25NM60N MOSFET) is shorted." So does it show as shorted between Source and Drain pin off the board, if not that snubber cap C825 which is connected in parallel with Source and Drain pin may be bad as TW2005 has indicated.

[momaka]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

There are 3 ICs on the primary side that are of interest: IC800, IC801, and IC601. List the part numbers of these so that we can figure out what each one is/does.

*edit*
Woops, looks like I am quite slow with my typing/analyzing. Please ignore my post.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

C825 has the following printed on its side.
R
221K
1KV

And measures 0.73nf out of circuit. It shows open if I read resistance.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

I found a different cap with the same markings in my parts bin. I swapped it out with no change.

[budm]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

So the cap was not shorted out to cause the fuse to blow, but the MOSFET shorted out, but that cap looks cooked so it should be replaced, it is snubber cap for the Q808.
So did you find the spec sheet for the ICs? At this point you need to check to replace bad components that you found bad and the PFC Controller IC.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

When that power MOSFET for the PFC Voltage shorted out, it's more likely to take out the Gate drive out put of the PFC Controller IC with it plus the resistors and diode for the Gate drive circuit.
You should get the P/N's of those ICs to get the spec sheet and the pinout. I would not replace the MOSFET without the IC at the same time.

Bud, I missed this post completely. I'm sorry to waste your time like that. Tri-State Module had this board for $70 with an additional 10% off and free shipping. New board installed and the set is back to working. I will look at that IC and see if I can't get it working anyway. Thanks for your help.

[tom66]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

For future ref, can you read off that burnt cap? Might help someone.

[johnboy1313]

Re: Sanyo DP46848-01 blown fuse on PSU, shorted MOSFET, lost unknown surface mount di

R
221K
1KV

That's all I can see on it.