Samsung LN46A550 Power Cycling

[dreamliner77]

Re: Samsung LN46A550 Power Cycling

Thanks to everyone in this thread but especially budm and Terryfictv! I was able to fix my LN46A550 that had reached the point of not staying on at all through hours of power cycles. I soldered 100uf caps in parallel with C102 and C131 and all seems fine now; it powers on just like it used to many, many months ago.

budm, first of all thanks for the extremely well documented pictures. Also, it seems that you've done a number of these repairs, have any failed that you've done the parallel fix on?

[v.i-guy]

Re: Samsung LN46A550 Power Cycling

thanx for your reply martino. I have looked up ccfl tubes and they say it could be a bad tube or a bad inverter. but would that cause it to power cycle.

[martino]

Re: Samsung LN46A550 Power Cycling

switching those doesn't really matter. To me it sound like you either have a bad connection to the ccfl tubes or a bad tube as tapping the tv helped.

[v.i-guy]

Re: Samsung LN46A550 Power Cycling

hello everyone I have the same problem as most guys do that have a 46 Samsung. I got this tv off of a guy for free he said it wouldn't turn on will when I got it home it turned on and worked for a couple of months but once in awhile the right side of the screen would go kinda black brown shady .if I moved the screen or tapped the tv it would go back to a good pic again. will I went to turn it on two days ago and the dreaded flashing red light and clicking. so I pulled the power supply and found that someone had replaced the capacitors but they were not soldered very will they were cold soldered so I resoldered them and put it back in and made a mistake I crossed the two plugins at the bottom of the board cn1808 cn1809. I still don't know I how I could have done that but the tv still came on for about 5 minutes and the picture was great but then it shut down again and back to the dreaded flashing and clicking. so did I fry something else by getting them backwards any help with would be great.

[Agent24]

Re: Samsung LN46A550 Power Cycling

WT61P6S is another microcontroller. It probably has an internal flash memory, rather than being one.

AP358 is an opamp, 4435B a MOSFET.

ATMLH844 and ATMLH834 are likely to be EEPROMs, but you need to write the other text on the chip, not just the first line. That first line is just part of Atmel's datecode, the 2nd (and maybe 3rd) lines tell the actual part number (in cryptic SMD code)

[Louis82]

Re: Samsung LN46A550 Power Cycling

ATMLH844
AP358
BOTTOM:
ATMLH834 (QTY: 3)
4435B

On the top of the board I see a IC that after checking specs it says that is a flash memory. Not sure if that might be the eeprom. Part number is WT61P6S

Thank you

[Agent24]

Re: Samsung LN46A550 Power Cycling

Can you post up all the part numbers for all the 8-pin chips? I can't read any of them in that picture. Are there any on the other side?

If it's none of those, it may be under the RF shield next to the processor, or might even be embedded into the CPU.

[Louis82]

Re: Samsung LN46A550 Power Cycling

I do have experience replacing eeproms. I have looked for the 8 pin ic but can't identify which one is. Here is a pic of board.

[Agent24]

Re: Samsung LN46A550 Power Cycling

Very unlikely for something built this recently. Most things now use serial-access EEPROMs, so they typically only have 8 pins. Older parallel ones used 28-32 pins or so.
The IC with many pins you speak of is probably the main CPU\GPU or other such processor\ASIC.

So you're looking for an IC with 8 pins that has a part number most likely 24C..., 25C..., 93C... or something similar.

[Louis82]

Re: Samsung LN46A550 Power Cycling

Is the EEPROM the big IC (many pins) located in the bottom of the board?

[Agent24]

Re: Samsung LN46A550 Power Cycling

Well you could always try copying the EEPROM from the working one?

[budm]

Re: Samsung LN46A550 Power Cycling

I know it's very strange. One just worked. I still have 2 more that are driving me crazy. change c102 twice already. Yes voltage is steady. Starting to think that maybe is the EEPROM. Any experience with defective eeproms on this board?

Sorry, no.

[Louis82]

Re: Samsung LN46A550 Power Cycling

I know it's very strange. One just worked. I still have 2 more that are driving me crazy. change c102 twice already. Yes voltage is steady. Starting to think that maybe is the EEPROM. Any experience with defective eeproms on this board?

[budm]

Re: Samsung LN46A550 Power Cycling

Is the Voltage across C102 steady? I never run into problem where C102 replacement does not fix the recycling problem.

[Louis82]

Re: Samsung LN46A550 Power Cycling

Here is a picture in case anybody needs one.

[Louis82]

Re: Samsung LN46A550 Power Cycling

Any other suggestion??

[Louis82]

Re: Samsung LN46A550 Power Cycling

STB on main board i get steady 5.1v

[budm]

Re: Samsung LN46A550 Power Cycling

Check the standby DCV to see if it is going up and down.

[Louis82]

Re: Samsung LN46A550 Power Cycling

Purchased new tantalum caps from digikey, soldered them on main board and still same. Tv clicks. Hey Budm, any suggestions?
Thank you!

[Louis82]

Re: Samsung LN46A550 Power Cycling

Hello guys,

I have same tv, same issue (cycling). Replaced what Budm has suggested C102 and C131. I used KMG 100uf 16v, I also replace MP2363DN and I still continue having same issue. Clicks and clicks, it comes on eventually and goes right off after 8 seconds. Any other suggestion? Thanks