Element ELCHW321 Catastrophic Failure

[mmartell]

I do not know the history of this set. A visual inspection of the power supply reveals:

Top of board:
open fuse
remnants of where a capacitor used to be.

Bottom of board:
surface mount component missing part of its top
a trace that changed colour considerably and no longer seems to be conductive
damaged 8 pin ic that shorted (leg blew up)

This is my first attempt to repair a PS. Where to start ?

[newtothis]

Re: Element ELCHW321 Catastrophic Failure

Ok lets start with some good quality pictures.

If this is your first PSU repair you have your hands full.

also what is the PCB part # on the PSU?

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

And the pics...

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Wow you're quick.

There are a couple of numbers on here. RSAG7.820.1459/ROH VER.F and HLP-30A11. I see the name Hisense as well.

[newtothis]

Re: Element ELCHW321 Catastrophic Failure

Ok I can troubleshoot to a degree... but not the 400 degrees that board got to! LOL!

If i looked at that my first thought would be .oO(How much are they on eBay!) LOL

Hope someone can help and good luck

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

About $40 but I'm more interestwd in the journey unless of course the parts were to excede that

[newtothis]

Re: Element ELCHW321 Catastrophic Failure

In this case I would suggest the replacement but if someone has a schematic for the board you could find the fried components... that being said that is not an easy repair.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

The ic and the surface mount component are part of what seem to be complimentary circuits so that might be helpful in finding part numbers. The fuse and the trace repair are no brainers. The cap value... no clue.

[newtothis]

Re: Element ELCHW321 Catastrophic Failure

The ic and the surface mount component are part of what seem to be complimentary circuits so that might be helpful in finding part numbers. The fuse and the trace repair are no brainers. The cap value... no clue.

Then figuring why this failure happened in the first place

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

ok the burnt out ic is an AN7530 and has been removed. The discoloured trace has in fact been evapourated and will need a jumper wire. The cap has been removed and the smd zener (?) tested in circuit as having 700 ohms one way and 1200 the other and had a voltage drop of half a volt in either direction. Then I cleaned the board.

Next step ?

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

That's a FAN7530 apparently...

What else should I check before I get into ordering parts ? I also do not know the value of the cap that blew up.

[PL519]

Re: Element ELCHW321 Catastrophic Failure

Hi mmartell,
look at this application note from fairchild, you´ll find good hints to get the values of the components which are totally burnt:

With the mains fuse o.c. i assume the mosfet is gone to heaven too. I would check for a short between drain and source. I would also replace the mains rectifier, even if it is tested o.K..

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Ok thanks for the input.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

Like a said earlier this is my first repair of this type so I'm hoping for some guru guidance as to where and how to test like I see in other threads.

But I will look up the proper way to test the Mosfet(s?) as soon as I find them lol.

[PL519]

Re: Element ELCHW321 Catastrophic Failure

Hi,
FAN7530 is a pfc (power factor controller), that´s the first stage of a smps after the mains rectifier. I´ve marked the rectifier in red, the mosfet is marked in yellow (maybe only the right one, maybe both in parallel). Any shorts?
I see the fuse had a rating of 4amps, so the trip point maybe much higher. This higher current flew through the rectifier and even if you don´t see any shorts or o.c. on that i would suggest to change it anyway. Could you take a photo from the solder side, which covers a bit larger area around the FAN7530, perhaps with a marking of the exploded cap?

[PL519]

Re: Element ELCHW321 Catastrophic Failure

sorry, my fault. Forgot the photo!

[PL519]

Re: Element ELCHW321 Catastrophic Failure

regarding the remnants of a cap on your first picture i think this must have been an electrolytic cap and also regarding the application circuit schematic on page 11 of fairchild´s application note the only elcap there is C6. The bom´s on the next pages list C6 as 22uF/25V for a 100W smps or 47uF/25V for a 200W smps. So if the blown cap is connected from pin 8 FAN7530 to ground this could point to the right dirction. The blown zener diode could be ZD1 in the application circuit schematic. Regarding the bom this a 1N4746, 18volt, 1W zener diode. A picture covering the complete area around the FAN7530 could clarify this.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

The first pic shows the area where the fan7530 was located and the blown cap just to bottom right at C809

The second shows the zener in relation to the first photo, though the pic is rotated.

[mmartell]

Re: Element ELCHW321 Catastrophic Failure

And btw you are right about the blown cap being between pins 6 and 8 of the FAN ic. Nice

[newtothis]

Re: Element ELCHW321 Catastrophic Failure

22uf 35v

is the number on your PSU RSAG7.820.1459? < IGNORE THIS, LOOK AT MY NEXT POST