Samsung LN55B650, No power, standby LED on

[Fullhouz]

I need some advice on troubleshooting this 15-month old Samsung LN55B650. Storms yesterday caused power surges and apparently caused this failure. One cap is bulging as seen in photo 6. When plugged in, there is a very low repeating buzzing sound coming out of the IP board which is on for two seconds then off for a couple seconds. My (dumb, newbie) three questions are:

Do I have a blown fuse? Based on research here, it appears a main board replacement is necessary; How can I confirm this? Should I replace all the caps on the IP board regardless?

Thanks,
Rob

[Liam.25]

Re: Samsung LN55B650, No power, standby LED on

I doubt a fuse has blown, its either capacitors on the psu or the main board has blown.

if your handy with a multi meter, some of the guys here will run you through checking voltages on the psu.

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

Thanks for the help. After a review of the IP board, all the caps are Samwha, Series WL and Series WB. There are (13) caps on the board. I'm planning to replace them as follows from biggest to smallest:

1.

2x WB, 450V, 100uF, 22 mm D x 35 mm H replaced with new

2x Panasonic TS Series, 450V, 100uF, 22 mm D x 35 mm H, Digikey part #P7427-ND,

2.

3x WB, 25V, 1000uF, 12.5 mm D x 20 mm H replaced with new

3x Panasonic FM Series, 25V, 1000uF, 12.5 mm D x 20 mm H Digikey part #P12379-ND,

3.

1x WL, 25V, 680uF, 10mm D x 20 mm H replaced with new

1x Panasonic FM Series,25V, 680uF, 10 mm D x 20 mm H Digikey part #P123390-ND,

4.

2x WL, 10V, 1000uF, 10 mm D x 16 mm H replaced with new

2x Panasonic FM Series,10V, 1000uF, 10 mm D x 16 mm H Digikey part #P12354-ND,

5.

3x WL, 50V, 47uF, 6.3 mm D x 11 mm H replaced with new

3x Panasonic FC Series, 50V, 47uF, 6.3 mm D x 11.2 mm H Digikey part #P10321-ND,

6.

2x WL, 50V, 33uF, 6.3 mm D x 11 mm H replaced with new

2x Panasonic FC Series, 50V, 33uF, 6.3 mm D x 11.2 mm H Digikey part #P10320-ND,


Please let me know if something above doesn't look right. Thanks, Rob

[joste]

Re: Samsung LN55B650, No power, standby LED on

For the beginning, try with the bulged guy (1000uF/25V). Even better: put 35V instead 25V since there's a lot of space on the board. Don't forget that all caps should be 105°C, just in case

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

I got the new replacement caps.

On the bottom of the power board, there are a couple of areas about 1 cm square in size that are discolored. It looks like a heat issue. One is centered on a resistor on the other side. Is this indicating a problem?

Thanks,
Rob

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

After a couple hours practice, the bulged cap got replaced to no aval. Next, checking the power; when I disconnect the connector from the power board to the main board, the TV backlight comes on and stays on. According to the troubleshooting manual (p.4-7), the next step is "Does proper Standy-by DC A5V appear at BD0229?"

Not knowning what this means; the voltage on the power board at the second pin labeled "SB" is 5.21V. It doesn't change when trying the power-on button or remote.

I checked the other 29 pins and the voltages appear right except maybe for pin 1 labeled "PS" at 0.75V and pin 12 labeled "INV-ON" at 3.77V.

Any help, specifically how to find and check voltage at BD0229 would be appreciated.

[PlainBill]

Re: Samsung LN55B650, No power, standby LED on

Let's take things in order. Samwha caps aren't the best. They usually are pretty good, but some production runs are known to be bad. Did you replace all the caps on the board, or only the one bulging one? I would have suggested replacing the three 1000uF, 25V caps.

The discoloration is not likely to be a problem, it depends on how severe it is. A slight discoloration is common, one area the shade of chocolate in an otherwise beige board would be of interest.

Please elaborate on

I checked the other 29 pins and the voltages appear right except maybe for pin 1 labeled "PS" at 0.75V and pin 12 labeled "INV-ON" at 3.77V.

Do you mean the voltages are within 5% of their nominal values? You are correct, 0.75 V is an unusual voltage, on the other hand 3.77 volts on INV-ON is reasonable - it's a signal from the main board to the inverter.

I'm downloading the service manual and will see if I can figure out what was meant by

"Does proper Standy-by DC A5V appear at BD0229?"

You are correct, a new main board may be necessary. Depending on the nature of a power surge, you could spend a long time chasing problems. But let's get the power supply issues sorted out first.

And I would like a few additional pictures.

1. The output connector of the power supply, with the labels visible.

2. A picture of the bottom of the power supply.

3. Pictures of the top and bottom of the main board.

PlainBill

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

Thanks for the help.

1. Yes, I believe the voltages checked with 5 percent but I will post all results tomorrow.

2. Attached are the requested photos.

3. One cap was replaced and the tv was tested to no aval. I have replaced two other 25V 100uF caps but have not tested the tv yet.

4. One of the photos shows the discolored areas on the back of the power board.

I appreciate the help.
Rob

[PowerAmpFreak]

Re: Samsung LN55B650, No power, standby LED on

The discolouration shown in photo #4 is nothing abnormal. Many of the components, especially power resistors like current sense resistors runs hot. Without using the proper standoff during production, it's natural to generate a degree of pcb discolouration.

[PlainBill]

Re: Samsung LN55B650, No power, standby LED on

The power supply has an unusual number of connections, several of which I do not understand. The PS pin is the product of a voltage divider; that .75 volts is not obviously incorrect. If you haven't done so, check the fuse.

I've marked up the pictures of the main board. I've circled several voltage regulators in blue - one on the top, three on the bottom. I'd suggest checking the output from those; they represent the few parts that it is possible to troubleshoot.

I have also circled an unusual looking IC in yellow. What is it's part number?

One thing I find incredible is that while I can identify a few linear voltage regulators, several bucking regulators, and a large number ceramic caps, I can identify only one electrolytic cap on the main board.

PlainBill

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

The power supply output pins 1 through 30 tested as follows:
1 PS 0.75V
2 SYNC 0V
3 SB 5.21V
4 GND 0V
5 GND 0V
6 GND 0V
7 18V 18.00V
8 18V 18.00V
9 GND 0V
10 GND 0V
11 GND 0V
12 GND 0V
13 5.1V 5.21V
14 5.1V 5.21V
15 5.1V 5.21V
16 5.1V 5.21V
17 GND 0V
18 GND 0V
19 13V 12.59V
20 GND 0V
21 13V 12.59V
22 13V 12.59V
23 INV-ON 3.77V
24 1-PWM 0V
25 5V-DETE-PWM 5.09V
26 GND 0V
27 0V
28 GND 0V
29 GND 0V
30 GND 0V

The two fuses on the power board were removed and check for continuity.

Three 1000uF, 25V caps were replaced and the TV was tested unsuccessfully.

The yellow circled IC is stamped with three lines:
S1 172B
33 VJ3
.5975

The parts list states:
....4 T0087 1203-005713 IC-POSI.FIXED REG.;S-1172B33-E6T1G,HSOP, 1 S.A

To test output on the blue circled voltage regulators. I plan to connect all the cables including the power cord to the wall and I will measure the voltage across the two pins of each. Please confirm this procedure, if you don't mind.

Thanks,
Rob

[PlainBill]

Re: Samsung LN55B650, No power, standby LED on

The power supply output pins 1 through 30 tested as follows:
<SNIP>
The two fuses on the power board were removed and check for continuity.

Three 1000uF, 25V caps were replaced and the TV was tested unsuccessfully.

The yellow circled IC is stamped with three lines:
S1 172B
33 VJ3
.5975

The parts list states:
....4 T0087 1203-005713 IC-POSI.FIXED REG.;S-1172B33-E6T1G,HSOP, 1 S.A

To test output on the blue circled voltage regulators. I plan to connect all the cables including the power cord to the wall and I will measure the voltage across the two pins of each. Please confirm this procedure, if you don't mind.

Thanks,
Rob

The voltages look good - or perhaps I should say none of the voltages look unreasonable.

The IC circled in yellow appears to be a variation of the 1117 family of LDO regulators. It's obviously a 3.3V regulator.

To measure the output voltages of the regulators circled in blue, use the bare copper around the mounting holes as a ground point. As an example, IC1101T is on the back of the board at about the 10 O'clock position. Measure from ground to the pin on the lower left, from ground to the tab, and from ground to the pin on the lower right. IF this is the regulator I think it is, lower left is Ground, tab is output, lower right is input.

Of course, IC502 (bottom at about 6 O'clock) is a variant of the familiar 7800 series of regulators and should follow that pattern - input on the bottom pin, tab is Gnd, output on the upper pin (as viewed in the picture).

I think it bears repeating - the chances of success are slim, but let's go through the steps.

PlainBill

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

Four IC voltage outputs were checked; Each of the pins that indicated voltage would range from 0.00V to the voltage value listed below over a six seconds cycle. I hope this makes sense.

On the front of main board
IC204
Top left pin 1.84V
Top middle tab 0.00V
Top right pin 3.29V

On the back of the main board
IC1101T
Bottom left pin 2.60V
Bottom middle tab 0.00V
Bottom right pin 2.60V

IC205 (near left edge in photo)
Left top pin 12.9V
Left middle tab 0.00V
Left bottom pin 8.90V

IC502
Right top pin 4.90V
Right middle tab 0.00V
Right bottom pin 8.86V

Is this indicating a problem with these regulators?

Thanks,
Rob

[PlainBill]

Re: Samsung LN55B650, No power, standby LED on

Four IC voltage outputs were checked; Each of the pins that indicated voltage would range from 0.00V to the voltage value listed below over a six seconds cycle. I hope this makes sense.

On the front of main board
IC204
Top left pin 1.84V
Top middle tab 0.00V
Top right pin 3.29V

On the back of the main board
IC1101T
Bottom left pin 2.60V
Bottom middle tab 0.00V
Bottom right pin 2.60V

IC205 (near left edge in photo)
Left top pin 12.9V
Left middle tab 0.00V
Left bottom pin 8.90V

IC502
Right top pin 4.90V
Right middle tab 0.00V
Right bottom pin 8.86V

Is this indicating a problem with these regulators?

Thanks,
Rob

Most of the voltages are easily identifiable.

IC204 appears to be a 1.8V LDO regulator.

IC1101T is either defective, or is not a regulator.

IC205 appears to drop the 12V input voltage to an intermediate value. No idea why.

IC502 takes the output of IC205 and drops it to 5V.

Obviously, the voltages are changing with the buzzing sound from the power supply.

I suspect the power surge did some major damage.

PlainBill

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

I received a new main board and I'm waiting for a new (iP) power board. What are the chances that I do damage to the new main board if I test it with the old power board?

...The Kentucky vs. Western Kentucky game is on in a couple of hours.

Thanks in advance,
Rob

[PlainBill]

Re: Samsung LN55B650, No power, standby LED on

I received a new main board and I'm waiting for a new (iP) power board. What are the chances that I do damage to the new main board if I test it with the old power board?

...The Kentucky vs. Western Kentucky game is on in a couple of hours.

Thanks in advance,
Rob

Go to a friend's home, a sports bar, or even in a extreme case, to your girlfriend's home with a dozen roses.

PlainBill

[Fullhouz]

Re: Samsung LN55B650, No power, standby LED on

With both the main board and IP board replaced, the TV is almost working perfectly. None of the HDMI inputs appear to receive a signal. Tried two HDMI cables, both cheapos, to no aval. But the original cheapo HDMI cable worked a month ago. The component input is working as a workaround for now.

For the record, the main board was $150 off ebay and the IP board was $85 off amazon.

Thanks for help in fixin my tv. Now all I need is to find a real football team to pull for.

Fullhouz