Samsung ln46c630 no back light

[gdawg]

Hi all, I have a ln46c630 Samsung with no back light. I have read all the posts on similar models and have replaced caps on power supply, Have tried unplugging mainboard which should turn on back lights and have snipped the jumper for flickering issues. All the posts have all gone as far as I have but nobody replied to what actually fixed it. I like to fix on component level and I believe its the power supply as I cant even hear any hum from the transformers. All voltages seem ok. I dont have a camera presently but the other posts have pictures of the same. Any help would be appreciated. I dont know if the other tv's on other posts got repaired or if they scrapped them. Thanks

[Alastair E]

Re: Samsung ln46c630 no back light

Well--IF all the voltages are OK--Its Unlikely to be the PSU...

A picture of the BL Board and PSU could help....

[nicholas1110]

Re: Samsung ln46c630 no back light

Hi, check fuse fs802s, if that fuse is good then it is most likely capacitor right above the fuse ci818. I have had to replace many of these capacitors on samsung power supplies. Hope this helps.

[budm]

Re: Samsung ln46c630 no back light

Is this the power supply/inverter board used in your TV?
http://www.shopjimmy.com/catalogsear...msung+ln46c630

[gdawg]

Re: Samsung ln46c630 no back light

Thanks for the responses. I will ck that cap nicholas1110 and thanks for the tip.
I have fixed probably 50 flat screen lcd's and plasma's and have gotten a lot of great info from this forum, so thanks again, I will report my findings, Gary

[gdawg]

Re: Samsung ln46c630 no back light

Sorry budm, I cant pull up the board while I am at work, but I know its a bn44-00341b

[gdawg]

Re: Samsung ln46c630 no back light

Just an update- I replaced the c1818 cap as per suggestion by nicholas1110 and everything is fine. i got it thru Mouser. Thanks, and another tv saved!!!!

[sputnikoff]

Re: Samsung ln46c630 no back light

I have similar issue with this tv .I had main fuse blown.After replacing one of those blue caps blown apart(Probe pic indicates which one) and shorted mosfet 13mn60n(Probe pic)
The backlight come on for a second or so and goes off.

[nomoresonys]

Re: Samsung ln46c630 no back light

So what exactly blew apart, the fuse, CP820 or CI18?

[sputnikoff]

Re: Samsung ln46c630 no back light

Blue cap blew cp820 and mosfet . I don't know value of cap above fuse c1818 however it looks fine,not shorted.

[nomoresonys]

Re: Samsung ln46c630 no back light

Can't always tell by looking, need a meter capable of testing capacitance to know for sure. If you used same type fuse, seems like short/over voltage issue. Is there a schematic for the power board? or trace out from the fuse testing everything along the way.

[sputnikoff]

Re: Samsung ln46c630 no back light

Know where get schematic

[sputnikoff]

Re: Samsung ln46c630 no back light

the value of c1818 is 450 nf on my cap meter.

[budm]

Re: Samsung ln46c630 no back light

So the parts in the PFC Voltage booster blew up and you replaced the blown parts, but are you now getting 380 ~ 400 VDC between the two legs of the main filter cap when the TV is turned on?

Power supply/inverter board: BN44-00341B.
This board is know for having low PFC Voltage and causes the backlights to flicker, the problem is caused by bad resistor network int he PFC Voltage feedback, but some people fix it the wrong by by cutting jumper J852 which defeat the LOW PFC Voltage shutdown protection circuit.
CI818 also goes bad and will have low capacitance and some time you can see it bulging on its side.

https://www.badcaps.net/forum/showth...ht=BN44-00341B

[sputnikoff]

Re: Samsung ln46c630 no back light

I will check and get back to you.And i don't think im getting that 380-400vdc.

[nomoresonys]

Re: Samsung ln46c630 no back light

If your voltage isn't getting the 380-400 or so, try replacing those four resistors that nelic6 did, with same value ones he used, it's post #22 of the link budm gives in post #14, looks like that fixed it.

[sputnikoff]

Re: Samsung ln46c630 no back light

Yes bud checked voltage lamps come on for a sec voltage goes from 165vdc to 159vdc ,then back to 163vdc.voltage taken at cp803 with negative on bridge-.power supply never goes to full voltage.

[sputnikoff]

Re: Samsung ln46c630 no back light

i guess i will remove power supply and bench test to see if its being loaded down.

[jason123]

Re: Samsung ln46c630 no back light

Gents, sorry hijacking this thread.. but anyone know where to buy this Ci818? My meter is reading 0 on the capacitance, so I'm assuming it needs to be replaced. Thanks

[R_J]

Re: Samsung ln46c630 no back light

I show CI818 as 0.47uf 450v, you can get one from digikey
PCF1574-ND