samsung ln46d630 power supply fuse blown and burn mark

[jmandawg]

Hi all,

picked up this curb alert TV. Looks like the fuse is blown, i don't have a fuse to replace is with, is it safe to short with something just to test it? There is also a burn mark in the white glue near a transistor so maybe the transistor is gone as well. Attached is a picture with the burn circled as well as the fuse that is blown.

Board is labeled as: BN44-00463A

What's my next best steps?

Thanks.

[diif]

Re: samsung ln46d630 power supply fuse blown and burn mark

Remove the glue around the burnt area to see what is damaged.
Do not use something in place of the fuse just to test, it clearly blew for a reason and you're likely to do more damage.

[neilc6]

Re: samsung ln46d630 power supply fuse blown and burn mark

Blown fuses almost always mean shorted diodes or FETs on the board. If you measure the resistance of one side of the fuse to ground, it will likely be a short that you need to track down.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Here is what's under the glue. It seems like the left pin on the transistor is shorted to ground. I'm not getting a zero reading but it's close. Also looks like the blue ceramic resistor has a chip taken out of it. Looks like it burn out the side of the transistor. What is that white glue for? Is it too prevent fires?

Transistor looks like it says CM0465R

[neilc6]

Re: samsung ln46d630 power supply fuse blown and burn mark

Yes that transistor is shorted. The glue is to prevent dust that may accumulate between high voltage pins from igniting. I have seen it a few times usually from tvs with indoor smokers.

If you bypassed that fuse, you could have tripped your circuit breaker in your house by plugging it in since you are shorting the AC. I use a plug in GFCI outlet for dodgy power supplies based on recommendations here.

[budm]

Re: samsung ln46d630 power supply fuse blown and burn mark

It looks like the blue disk snubber cap had shorted out, remove it and see if the shorts goes away.
BTW, FSCM0465 is a SMPS IC not MOSFET. You need to check the internal MOSFET of that IC to see if it is shorted out or not

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Ok I'll remove the blue disk tomorrow and check for the short. How do I check the mosfet of the IC? The right pin on the IC broke when I was removing the glue.

Here is a better picture. How do Find a compatible blue cap. It looks like it says 101 1K.

[budm]

Re: samsung ln46d630 power supply fuse blown and burn mark

1) So did you check the the resistance of that blue disk cap to see if it shows as shorts?
2) The inetrnal MOSFET can be checked for shorts by measuring pin 1 and pin 2 of that IC, see the spec sheet I provide that shows the pinout of the IC. BTW, if you test it again without the blue cap in place as you did in your post #4, does it show as shorts?
3) The blue high Voltage ceramic cap is 100pF 1000V, I would replace it with 2000V rating instead.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

The blue cap is measuring around 2k ohms. I removed it from the board and the short is gone.

I measured between pins 1 & 2 on the IC and there is no short there. Unfortunatly since i broke off a pin when removing the glue i also removed the IC.

Also i misread the IC it's actually a GM0465R (GM not CM).

1. Would the next best steps be to replace these 2 parts and the fuse and see if the short still exists.

2. Is this the correct IC replacment: https://www.digikey.com/products/en/...=1&pageSize=25

3. is there a better store to buy the parts from?

Thanks

[nomoresonys]

Re: samsung ln46d630 power supply fuse blown and burn mark

You can try ebay for the cheaper shipping but hard to beat digikey for reliability.

[neilc6]

Re: samsung ln46d630 power supply fuse blown and burn mark

You are lucky that part is still in stock at Digikey and not obsolete. Ordering ICs from Aliexpress is quite the crap shoot and may be the only option for obsolete ICs.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

For the IC GM0465R what is the difference between L-forming W-forming and U-forming and will it make a difference which one i use?

Also can i replace the ceramic fuse with a glass fuse like this (same amps and voltage): https://www.digikey.com/product-deta...mSeq=331601576

They don't seem to have any ceramic ones in stock unless they are imported (tariffs/extra shipping).

[neilc6]

Re: samsung ln46d630 power supply fuse blown and burn mark

Not sure how you are searching but here's a ceramic

https://www.digikey.com/product-deta...212-ND/1008984

If you download the datasheet from Digikey, the physical specs at the end show the different forming packages. Just how the pins are pre-bent.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Awesome thanks for the help, saved me from buying the wrong part. I will probably have to order that IC from china/ebay as digikey doesn't have it with the correct pin forming.

[budm]

Re: samsung ln46d630 power supply fuse blown and burn mark

Are you going to get the replacement ceramic cap too?

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Yeah, i need the IC, cap, and fuse. I've having a hard time sourcing them all from the same place. Prob just get them all individually on ebay.

[neilc6]

Re: samsung ln46d630 power supply fuse blown and burn mark

Just order everything from Digikey. You can just rebend the pins.

Here is the cap https://www.digikey.com/product-deta...6PH-ND/2356736

[budm]

Re: samsung ln46d630 power supply fuse blown and burn mark

i would order more than one piece each in case of messing up the repair.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Thanks guys i just ordered 2 of everything from digikey. I wasn't sure if the IC would still screw into the heatsink if i bent the pins, but hopefully they are long enough. Will update once it all gets here. Thanks.

[jmandawg]

Re: samsung ln46d630 power supply fuse blown and burn mark

Ok guys parts came today. two of the IC pins were a little bit short so I had to solder on some extensions made from the disk capacitor pins. I got everything soldered on and I checked for the short and it was gone. I got everything assembled back together and turned the TV on and it worked! I attached a pic of the extensions to the IC pins. I think they should be ok.

Thanks for all the help guys. You are all awesome!