Samsung LN26B460B2D

[Bobz]

Hey all,
I have fixed two LCD TV's, a computer monitor and motherboard thanks to this website and everyone that supports and contributes to it. I am now fixing a LCD TV, Samsung LN32B460, and haven't found any threads on it. The symptom is no power. The power led[RED] does come on, it blinks 5 times then goes out. It will however stay lit if you press it again but no picture, no sound, no back light. I opened up the back and examined the power supply. No Bulging caps, burn marks, or bad solder joints, visually looks okay. I tested both fuses and they're good. I tested the output to main/logic board thanks to a voltage pinnout printed on the board, and everything checks out.

I turned off the lights to see if there was ANY backlight activity at all, there was none. I also performed the flashlight test, there seems to be no image at all. I would like to test the inverters, but am not exactly sure how to do this.

Since no light OR image, and powerboard seeming to be in pretty good shape my head turns to the main/logic board. Everything visually looks okay, except for the underside which is covered it what looks like spilt coke~a~cola.(which i doubt because every surrounding areas is completely clean including topside of board.) The other thing I noticed about the main/logic board is that when it is hooked up completely and tv is in "on" position(LED on) the heatsink on he processor gets VERY HOT to the touch. I wish I had an infrared thermometer to find an exact temp., but i couldn't hold my finger on the sink for more than two seconds without instinctively pulling away.

Anyway, am I right to suspect the main/logic board in this case? And if so what are some ways to go about testing it? (I am ready to replace it if needed)
-Are there any further tests that you suggest I make on the power supply?

Thank you


Update: I have replaced 5 caps on the upper right side of the board with no change in activity. The caps were
25V 1200uf
10V 1200uf -- All caps by Sam Young
3X 50V 474uf

I will replace the rest of the caps, just need to take a trip to the electronics store.

[PlainBill]

Re: Samsung LN26B460B2D

The symptoms indicate a problem on the main board. Unless you have unusually sensitive fingers, I would say the processor has been fried. You could check the LDO regulators around it, but if it has gotten that hot, I'd suspect it is damaged.

PlainBill

[Bobz]

Re: Samsung LN26B460B2D

Hi Plain Bill, Thanks for the answer. I was able to get my hands on exactly the same Main Board on ebay. Luckily the guy was close enough and I was able to pick it up yesterday. Anyway, put in the new board connected everything up, and I heard the power on chime! Unfortunately, that was it. Still no picture or backlight. I swapped the boards a couple of times and it was consistent, that my board produced no chime and the new board did. But still no backlight or picture(tried flashlight test). The guy I bought it from said in was 100% working, but like I said I don't know how to test these boards.

Should I take this board back and try ordering a new one?
or Are there more tests that i should perform?

I am also curious about the Silver box on the upper left part of the power supply?

[pamr4]

Re: Samsung LN26B460B2D

Check Zenner diodes and the resistor. Picture quality isn't that good. Tell me please the the color band of the resistor placed next the ZD.

[Bobz]

Re: Samsung LN26B460B2D

Check Zenner diodes and the resistor. Picture quality isn't that good. Tell me please the the color band of the resistor placed next the ZD.

Hi, Thanks.

I'm assuming your referring to the zeners and resistor located in the middle of the power supply.The colors on the resistor are Yellow, Black, Silver and Gold(.4 ohm) and tested right in the ballpark with my analogue MM.

As for the zeners, I am not 100% how to test these accurately. But they read:

Anode -> cathode
start at 75k ohms then approach infinite

Cathode -> Anode
varies when i change the ohm test voltage, for ex:
RX1: 29 ohms
RX10: 200 ohms
RX100: 1500 ohms
RX1K: 12K ohms with the exception of the one closest to the resistor which reads 19k ohms

All these reading were taken with the components in circuit(including the resistor)(I did not de-solder anything)

I know this not the best or even correct way to test these zeners, but they show consistency in all tests with the exception of the slight difference on the last one. I researched a little about correct testing, but do not own a variable power supply and cannot tell the zener value with the components still in-board. If there is a better test please let me know or point me in the right direction. If not I will be looking tomorrow

[Dgtech]

Re: Samsung LN26B460B2D

I got a quick little test for you to do. Disconnect the cable that connects the power board to the main board then power up the set with the side button (bottom I think). At this point, the backlights should come on. Post the results.

This will not fix anything but it should at least confirm that the CCFL's (lamps) are working. I have a samsung LN32B360C with almost exact symptoms. I even swapped out the mainboard with the same result.

[Bobz]

Re: Samsung LN26B460B2D

I got a quick little test for you to do. Disconnect the cable that connects the power board to the main board then power up the set with the side button (bottom I think). At this point, the backlights should come on. Post the results.

This will not fix anything but it should at least confirm that the CCFL's (lamps) are working. I have a samsung LN32B360C with almost exact symptoms. I even swapped out the mainboard with the same result.

Hi,

If I disconnect my mainboard from my powersupply, the powersupply is isolated from the on/off button.(see picture) I did look at your thread and tried disconnecting the flat-ribbon to the T-conn from the mainboard. When I powered it on disconnected from the T-conn, same exact symptoms.

I also tried jumping the stby 3.5V to the on/off pin with a resistor with nothing.

What did you do to solve your problem?

[Dgtech]

Re: Samsung LN26B460B2D

I still have the set with the problem, I just moved on to another set until someone posts a reasonably priced power supply board on ebay. It's only a three board TV set. T-conn, Power, and Mainboard. I'm usually better at diagnosing at least what board the problem is on however, in this case...I missed on the first shot. There's nothing left but the power supply board.

[Bobz]

Re: Samsung LN26B460B2D

Hi, Just an update. I finished replacing all capacitors on the power supply as well as touched up all possible bad solder joints. Everything still appears good, voltages match the pinnout chart and solder joints all look clean. The new Main board resulted in producing the power on chime, which my old board didn't do. However, still no picture and no backlight. Surprisingly not a lot of info about these tv's on the web.

[Sniper82]

Re: Samsung LN26B460B2D

Im of no help sorry but I have a RCA L32HD31 I posted on here with the exact problem. I get power light but nothing happens. All power reading are fine on pinouts and 24v to the inverter. I'm puzzled. We probably share about the same problem. Just pinpointing it is key.

[Sniper82]

Re: Samsung LN26B460B2D

fixed my problem:
https://www.badcaps.net/forum/showthread.php?t=16041

am sure its not the same case with yours but thought I'd post it.

[Dgtech]

Re: Samsung LN26B460B2D

To follow up with my set, I finally took the advice to change out the power board against my best judgement and the damn thing worked like a charm. Strange!!!.

[Dgtech]

Re: Samsung LN26B460B2D

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