Samsung Ln55b650t1f Part Identification

[philtvman]

This TV will display a standby light, but does not turn on. Light will turn off and on again if you press it.

Looking at the main board, this little inductor looks to be blown. It has markings of "4R7 941" on the top. Can somebody confirm for me if this is a compatible part?

DigiKey Part
Mouser Part

[philtvman]

Here is the main board it came off of

[ngth82]

The first inductor is a 4.7uH. What's the diameter of the part?

The first line indicates the value. The second line is likely the production date code / lot code.


Did this come off of the pads around the barcode label?

[ngth82]

The parts you cross referenced from digikey and mouser should be fine.

What's currently wrong with this inductor? Is it OPEN?

What's the DC resistance across the two pads?

[budm]

Originally Posted by ngth82

the parts you cross referenced from digikey and mouser should be fine.

What's currently wrong with this inductor? Is it open?

What's the dc resistance across the two pads?

+1

[philtvman]

Originally Posted by ngth82

The parts you cross referenced from digikey and mouser should be fine.

What's currently wrong with this inductor? Is it OPEN?

What's the DC resistance across the two pads?

Yes it came off the pads by the barcode, and yes it is currently open.

[ngth82]

Originally Posted by philtvman

Yes it came off the pads by the barcode, and yes it is currently open.

Your meter is in resistance (Ohm) mode. It says 0.00 Ohms.
An inductor should register as 0 Ohm (for all practical purposes). That inductor appears to be fine.

Your meter should read "OL" (open loop), or similar, when your probe tips have no connection - similar to the reading when you just have the two probes not connected to each other.

Lets back up a few steps:

1. What brought you to the conclusion the inductor is bad?
2. What was wrong with this main board?

[philtvman]

Originally Posted by ngth82

Your meter is in resistance (Ohm) mode. It says 0.00 Ohms.
An inductor should register as 0 Ohm (for all practical purposes). That inductor appears to be fine.

Your meter should read "OL" (open loop), or similar, when your probe tips have no connection - similar to the reading when you just have the two probes not connected to each other.

Lets back up a few steps:

1. What brought you to the conclusion the inductor is bad?
2. What was wrong with this main board?

I was always under the impression inductors should be between 1Ω-11Ω, is this not true? Are here any other methods to verify it is working properly?

1. Physically it appears to have two burned score marks on either side
2. All voltages on PSU looked good. TV has a standby light that will momentarily turn off for 2 seconds when the power button is pressed. No picture displays. Unplugging the Main from the PSU does turn on all the backlights, no issues there.

[ngth82]

Can you get some good clear head on shots of the main board? Preferably in natural light - no flash.

Look at your meter. Turn it on and into resistance mode.

• When you don't have the probes touching each other, what reading do you get? (OL or something similar).
• Touch the probes together -- what reading do you get now? (0.00 ohm, or something under 1 ohm is what we're looking for.).

If you get something in the ~10 ohm region, i'm assuming that you didn't break through the thin layer of oxidation on the probe. A good test is to get a piece of copper and lightly "jam" the tip into the copper for a good connection.

Anyway, back to your TV: the inductor should have 0 resistance (for the sake of this discussion). There are parasitic resistances for it in a "real inductor" vs an "ideal inductor" (quick google search will have some physics background for this)

Do you have a photo of the board before you removed the inductor?

I'm assuming the connector by the barcode goes to the power board.

• Please post voltage readings with everything connected when the TV is OFF
• Post voltage readings with the TV is ON?

Make a table like this (example). Give the pin number. The signal name (as shown on the silk screen on the board), the OFF voltage, the ON voltage. Wrap it with the "code" block when you edit in "Go Advanced" mode to format it...

Pin	SIG	V_OFF	V_ON
1	PWR_ON	0	3.329
3	20V	0	21.26
5	GND	0	0
7	GND	0	0
9	3.5V	3.49	3.438
11	3.5V	3.49	3.438
13	GND	0	0

[ngth82]

Also, what's the full service code number for this TV?

LN55B650T1Fxxx

Maybe LN55B650T1FXZA?

[philtvman]

Originally Posted by ngth82

Can you get some good clear head on shots of the main board? Preferably in natural light - no flash.

Look at your meter. Turn it on and into resistance mode.

• When you don't have the probes touching each other, what reading do you get? (OL or something similar).
• Touch the probes together -- what reading do you get now? (0.00 ohm, or something under 1 ohm is what we're looking for.).

If you get something in the ~10 ohm region, i'm assuming that you didn't break through the thin layer of oxidation on the probe. A good test is to get a piece of copper and lightly "jam" the tip into the copper for a good connection.

Anyway, back to your TV: the inductor should have 0 resistance (for the sake of this discussion). There are parasitic resistances for it in a "real inductor" vs an "ideal inductor" (quick google search will have some physics background for this)

Do you have a photo of the board before you removed the inductor?

I'm assuming the connector by the barcode goes to the power board.

• Please post voltage readings with everything connected when the TV is OFF
• Post voltage readings with the TV is ON?

Make a table like this (example). Give the pin number. The signal name (as shown on the silk screen on the board), the OFF voltage, the ON voltage. Wrap it with the "code" block when you edit in "Go Advanced" mode to format it...

Pin	SIG	V_OFF	V_ON
1	PWR_ON	0	3.329
3	20V	0	21.26
5	GND	0	0
7	GND	0	0
9	3.5V	3.49	3.438
11	3.5V	3.49	3.438
13	GND	0	0

Thank you for your assistance, I will test the pins tomorrow. Just to be clear, you are wanting me to resolder the inductor onto the main board and test it the voltages with the unit powered off and on? The TV never really turns on, but the standby light will turn off for a couple seconds before going back to a black panel with standby light on.

[budm]

Originally Posted by ngth82

can you get some good clear head on shots of the main board? Preferably in natural light - no flash.

Look at your meter. Turn it on and into resistance mode.

• when you don't have the probes touching each other, what reading do you get? (ol or something similar).
• touch the probes together -- what reading do you get now? (0.00 ohm, or something under 1 ohm is what we're looking for.).

if you get something in the ~10 ohm region, i'm assuming that you didn't break through the thin layer of oxidation on the probe. A good test is to get a piece of copper and lightly "jam" the tip into the copper for a good connection.

Anyway, back to your tv: The inductor should have 0 resistance (for the sake of this discussion). There are parasitic resistances for it in a "real inductor" vs an "ideal inductor" (quick google search will have some physics background for this)

do you have a photo of the board before you removed the inductor?

I'm assuming the connector by the barcode goes to the power board.

• please post voltage readings with everything connected when the tv is off
• post voltage readings with the tv is on?

make a table like this (example). Give the pin number. The signal name (as shown on the silk screen on the board), the off voltage, the on voltage. Wrap it with the "code" block when you edit in "go advanced" mode to format it...

pin	sig	v_off	v_on
1	pwr_on	0	3.329
3	20v	0	21.26
5	gnd	0	0
7	gnd	0	0
9	3.5v	3.49	3.438
11	3.5v	3.49	3.438
13	gnd	0	0

+1

[ngth82]

Yep. Solder the inductor back on.

Take readings with the tv off.
Then take readings with the tv on. This may take several on-off cycles. Since some of them will likely decay since the tv doesn’t turn on all the way.

[budm]

https://www.badcaps.net/forum/attach...1&d=1586578260
What is the P/N of that 8-pin SMD IC connected to that inductor?

[philtvman]

Originally Posted by ngth82

Can you get some good clear head on shots of the main board? Preferably in natural light - no flash.

Look at your meter. Turn it on and into resistance mode.

• When you don't have the probes touching each other, what reading do you get? (OL or something similar).
• Touch the probes together -- what reading do you get now? (0.00 ohm, or something under 1 ohm is what we're looking for.).

If you get something in the ~10 ohm region, i'm assuming that you didn't break through the thin layer of oxidation on the probe. A good test is to get a piece of copper and lightly "jam" the tip into the copper for a good connection.

Anyway, back to your TV: the inductor should have 0 resistance (for the sake of this discussion). There are parasitic resistances for it in a "real inductor" vs an "ideal inductor" (quick google search will have some physics background for this)

Do you have a photo of the board before you removed the inductor?

I'm assuming the connector by the barcode goes to the power board.

• Please post voltage readings with everything connected when the TV is OFF
• Post voltage readings with the TV is ON?

Make a table like this (example). Give the pin number. The signal name (as shown on the silk screen on the board), the OFF voltage, the ON voltage. Wrap it with the "code" block when you edit in "Go Advanced" mode to format it...

Pin	SIG	V_OFF	V_ON
1	PWR_ON	0	3.329
3	20V	0	21.26
5	GND	0	0
7	GND	0	0
9	3.5V	3.49	3.438
11	3.5V	3.49	3.438
13	GND	0	0

Full Model: LN55B650T1FUZA
P/N for the SMD near the Inductor: Z1021HAI

Here are the voltages I ended up with. I initially checked all capacitors on the PS and they verified okay.

Pin #	Sig	v_off	v_on
1	PS	0	0.1
2	Sync	0	0
3	SB	5.18	1.3
5	GND	0	0
7	18V	0	1.5
9	GND	0	0
11	GND	0	0
13	5.1	0	0.5
15	5.1	0	0.5
17	GND	0	0
19	13	0	0.04
21	13	0	1.7
23	INV-ON	0	0
25	E-PWM	0	0.6
27	5V_DET	0	0
29	GND	0	0
30	GND	0	0

Thanks again for your help

[budm]

What is the power supply board P/N? BN44 -?????
Your readings do not look right at all.

[philtvman]

Originally Posted by budm

what is the power supply board p/n? Bn44 -?????
Your readings do not look right at all.

bn44-00268a

[budm]

What DC V do you have between the two legs of the main filter caps (two 450vdc LARGE CAPS laying on the side in t he HOT DEADLY SIDE of the circuit) when power switch is OFF and when it is on?

Post #15:
"3 SB 5.18 1.3"
Are you 100% sure that the SB (5V Standby power supply) drops down to 1.3V? I cannot see why you will have standby LED comes on when standby power supply drops down to 1.3V.

[ngth82]

+1 to BudM and the big scary cap comment. It's no joke. Don't die.

Just getting to my e-mail... standby goes down to 1.3V? STBY isn't loaded down when the TV is off (e.g it's within nominal), and shouldn't be when the TV is on.

Edit: also, you are missing a few pin numbers... You have pins 1, 2, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 30... where are the rest?

[philtvman]

Originally Posted by budm

What DC V do you have between the two legs of the main filter caps (two 450vdc LARGE CAPS laying on the side in t he HOT DEADLY SIDE of the circuit) when power switch is OFF and when it is on?

Post #15:
"3 SB 5.18 1.3"
Are you 100% sure that the SB (5V Standby power supply) drops down to 1.3V? I cannot see why you will have standby LED comes on when standby power supply drops down to 1.3V.

Voltage between filter caps
Power Off with Main Disconnected from PS: 387
Power Off All Connected: 168
Power On: Spikes to 387 and drops back to 168

Tested the SB and yes, same result. Steady at 5.18 with Power Off.
When Powered on, voltage jumps from 5.18 -> 3.31 -> 0.155 -> 1.3 -> 1.6 -> OL -> 5.18 (all in about 2 seconds)...when the button is pressed and these voltages are bouncing around, the standby light turns off.