Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

[fun148]

I have a dead Sub PCB (BP96-01726B) with no 16V output. I have found out that the resistor is blown, but I am having trouble identifying the specification of the resistor. Could any one please help? Thanks.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

From what I can see, the band colors seem to be (from left to right):

orange-orange-black-gold-white

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

33 Ohms 1/2W. MOX type. What resistance reading did you get using Ohm meter?

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

Thanks, budm. I did not really check the resistance, I just checked the voltage before and after the resistor. Before the resistor was 320V, after the resistor was almost zero.

Would you please explain how you can tell the wattage of the resistor?

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

"Would you please explain how you can tell the wattage of the resistor?"Looking at the pictures and the component next to it.
You can measure the dimension of the resistor and then check the dimension on the resistor you are going to order.
The resistor may have been blown open due to too much current draw due to shorted circuit.
Please post good clear straight shot pictures of the whole board top side and the bottom side so we can trace the connection to find out what the function of this resistor is.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

Would bad caps cause the blown resistor? I actually just replaced the 450V big cap and the 4 25V small caps.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

When I order the resistor, say in Digikey.ca, do I need to specify "MOX" type? I can only find Mini-Mox and Maxi-Mox under the "Series" heading.

Also, I accidentally use the OHM setting on my multimeter to check the live voltage of the sub PCB input power plug (320V), could there be any damage done to the multimeter? Right now I dont see anything abnormal about the multimeter in checking voltage and resistance.


Sorry for all the questions, as I know very little about electronics. Thanks.

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

It looks like that resistor is for feeding the Voltage to that 7-Pin IC pin 5.
You need to get the P/N as printed on top of the IC to find out what it does and to get the pinout of the IC.
That IC may be shorted out and cause the IC to resistor to blow, you can check the resistance between that pin 5 where one leg of the resistor is connected and the Negative leg of the 450VDC cap to see if it shows low resistance.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

It looks like that resistor is for feeding the Voltage to that 7-Pin IC pin 5.
You need to get the P/N as printed on top of the IC to find out what it does and to get the pinout of the IC.
That IC may be shorted out and cause the IC to resistor to blow, you can check the resistance between that pin 5 where one leg of the resistor is connected and the Negative leg of the 450VDC cap to see if it shows low resistance.

yes, the resistor is for feeding the Voltage to that 7-Pin IC pin 5.

The printing on top of the IC are:
B821
LNK304PN
52889H

The resistance between that pin 5 where one leg of the resistor is connected and the Negative leg of the 450VDC cap is 1.003kohm.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

Let me give you a brief history:

A few days ago, my TV started behaving exactly as described in the service manual:

"Protect Status

1. Attempting to turn the LED ASSY on fails repeatedly
If turning the LED on fails, the set automatically tries turning the LED ASSY on 3 times. If all attempts fail, all LED's on the front panel will blink. Check the LED ASSY, LED Driver and the Sub power or SMPS and replace them if necessary"

The TV will automatically go through this "Protect Status" steps as soon as I plug it into the wall electrical outlet (i.e. without me pushing any button either on the TV or the remote). When all the LED's start blinking at the same time, all the fans will be turned off. The LED's and the center on/off button light can only be turned off by pulling the plug.

I checked this forum and decided to open up the back of the TV to check for bad caps. The only ones I could find were all on the sub PCB, the big 450V cap and 2 of the 4 25V caps had swollen tops. I did NOT check anything else and went directly to replace the big cap and all the 25V caps.

After the replacement, the TV still did not work. I then started checking voltages and found this blown resistor.

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

OK, it is switching buck converter.
Check the resistance between D (5) and S (7) pin.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

OK, it is switching buck converter.
Check the resistance between D (5) and S (7) pin.

it is .996 kohm.

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

It is bad, it should show as open circuit. I would take that IC out and test it off the board again.
Since that high voltage form the 450V cap went through that bad IC, lots of components could have been damaged also because the circuit is made to produce low output Voltage to feed other circuit down the line.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

It is bad, it should show as open circuit. I would take that IC out and test it off the board again.
Since that high voltage form the 450V cap went through that bad IC, lots of components could have been damaged also because the circuit is made to produce low output Voltage to feed other circuit down the line.

understand, I will try to take it out and test it. The pins are so close together I am afraid I may have problem solder them back on ....is there any trick to do it, as I didnt do a good job in soldering the replacement caps...I think may be I put too much solder.

Once I have it out, other than pin 5 and pin 7, are there any other pins I should check?

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

The resistance between D (5) and S (7) pin off the board is more or less the same as before = 1.052 kohm. I guess that means it has to be changed, right?

Should I also change all the components in between the resistor and the 450V caps, just to be on the safe side? or is there a way to check them?

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

The diameter of the resistor is about 2.5 to 3.0 mm
the length of it is about 8 to 9 mm
From Digikey.ca, the 33 ohm resistors which fit the above diamensions can either be 1W or 0.5W.
Only the Panasonic ERG-1SJ330 one is metal oxide film, but it is 1W.

I am going to order all my parts from Digikey.ca, so can you please advise me which specific resistor I should choose? As I have no idea if I could use a higher or lower wattage rating of resistor, or if MOX resistor is not available, what else I should use.

Thanks.

[CapLeaker]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

Digikey part#: RSMF1JT33R0CT-ND
That should fit

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

Digikey part#: RSMF1JT33R0CT-ND
That should fit

CapLeaker, thanks for the suggestion. But I am worry about what the proper wattage of the replacement resistor should be more than the size. As budm told me to match up the size for the proper wattage, but I ended up finding within the original resistor dimension range, it could be either a 1W or 0.5 W. So I dont know which wattage resistor I should use for replacement.

[budm]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

I would or one of each because they do make small body with the same Wattage as the bigger body.
What worry me the most are the circuits and the components connected to the Source side, you need to carefully check them really well, since the high Voltage may have apper on the S pin before the resistor bunt open.

[fun148]

Re: Samsung HL61A750 TV Sub PCB (BP96-01726B) resistor identification

"I would or one of each because they do make small body with the same Wattage as the bigger body." <<< after I receive them, how ma I going to decide which one to use, as they will be all more or less the same size?

"What worry me the most are the circuits and the components connected to the Source side, you need to carefully check them really well, since the high Voltage may have apper on the S pin before the resistor bunt open." <<< As I said before, I am a newbie in electronics. I dont even know what most components are by just looking at them, so you can tell how much I know in "checking" them. When you talked about "the circuits and the components connected to the Source side", how many components are there? Can I just replace them all? But I would surely need your help to identify what they are and what their specifications are. As my thought is even if they are not dead yet, they may have been kind of damaged already, so if there are not too many components, I would rather replace them all to have a more reliable board for the long term.