Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

[Mad Capper]

I got this and all I was told was that one day it did not turn on, no other details were provided. See attached for initial images of PSU when I received it. As you can see from the photos I had to fix the obvious things to even try to do more troubleshooting. I am curious why these failed so catastrophically.

I have highlighted the parts that I have already replaced in yellow and the ones that I believe need to be replaced in blue in the attached schematic.

First I replaced
FP801s fuse
CB806 capacitor
ICB801S Q0165R (I replaced it with the SOP instead of DIP and made some legs to go through the board, not pretty but I hope effective, not pictured)
DZB806 Z02W9.1VY zener diode
DB806 1N4148 diode

Dim bulb tester showed a short and I found and replaced
QP801S 11N60C3

Plugged it back in with 100W bulb and the bulb flashed bright about 4-5 times. After that and on subsequent power ons nothing. Tried it without the dim bulb tester and fuse did not blow so I guess no dead shorts. But in both instances I noticed a smell of something getting too hot. The IC getting too hot is ICM801 MC33067.

At that point there was only a standby voltage of 5.2V on pin 3 of CNM801, main cap CP815 shows solid 158V, voltage on ICB801S is 8V if I can recall, no other voltages on that connector and ICM801 does not get hot instantly. However, this only occurs when CNM801 is disconnected from the mainboard.

When CNM801 is connected to the mainboard all of these voltages continually fluctuate and ICM801 gets hot instantly(5-10 seconds), I shut it off at around 180°F.


Further research led me to find that QB802 KD1691 is shorted and ZD805 Z02W15VY is open. I have not replaced those yet.


Currently, checking pin to pin on ICM801 pin 4-13-14 have continuity. I desoldered those pins to isolate it from the rest of the circuit and they still have continuity. According to the block diagram of the MC33067 it would seem that pin 13-14 continuity means that it is bad and needs replaced. Is that correct?

Currently, checking pin to pin of ICP801s FAN7530, 4-6 have continuity but that seems to be due to the resistor RP820 having low resistance and my meter beeping below 40 Ω, as there is not continuity between those pins when the resistor is removed.


Correct me if I am wrong but I have read that the order of things to check out for the PSU is first I need standby voltage then the PFC section turns on and boosts the voltages then the secondary voltages are created, in this case I assume it is from the ICM801 MC33067, correct? If this is correct I would like to be able to know if ICP801s FAN7530 is good, if possible, before replacing them. Not knowing about SMPSs I do not know how these two interact.

I have read about shorting the Standby and ON/Off on the connector to the mainboard to see if the PFC ICP801S is working, but with the other problems I do not know if they should be fixed first or if it can be done with out damaging other components. Knowing the components I mentioned above probably need replaced is there are way to test the PFC IC without them functioning or do they need to be replaced first?

Does the fluctating voltages when the CNM801 is connected to the mainboard, but solid when not point to a mainboard failure or do these things on the PSU need to be fixed before determining if the mainboard is also at fault? It makes me wonder about things I hear about power surges coming through the HDMI and causing failures of components on the PSU and perhaps damaging the mainboard in the process.

Any assistance is appreciated. Thank You


IC Datasheets

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

So I take it that there is no way to figure out if the mainboard is bad if the PSU is not working completely. I would really like to figure that out.

I was wondering if feeding it 5V from a cell phone charger with it disconnected from everything except the front buttons would help to determine if the mainboard regulator is making the 3.3V of whatever the On/Off voltage is supposed to be. I would assume I would need some sort of resistor to limit its current. Or perhaps this is inadvisable.

Still can't figure as to why the voltages fluctuate when the cable it plugged into the mainboard.

Nor how I could go about isolating and checking if the PFC IC is working without the other parts functioning.

Thus any thoughts that can help lead to a resolution is appreciated.
Thank You

[dick_barton]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Further research led me to find that QB802 KD1691 is shorted and ZD805 Z02W15VY is open. I have not replaced those yet.

Have you now replaced these components and what is the current state.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

I have not replaced those components yet as I am trying to figure out the other items if possible before I put more parts into something that may have other issues that may be irreparable.

[dick_barton]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

If the parts are not replaced then it is difficult to make a decision on what is or is not working. This is always a problem when carrying out repairs, that you test as much as possible all components on the board using your meter in ohms, and diode mode as applicable.

What you do know is that you do not have the higher voltage of 259V on Q601 so the oscillator is not driving the primary of T601. If it's not being driven you will have no secondary voltages.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

What you do know is that you do not have the higher voltage of 259V on Q601 so the oscillator is not driving the primary of T601.

I am not seeing Q601 or T601 in the schematic. Did you mean QM801 and TM801S?

I have tested as much as I can including all of the SMD components as best I can without removing them.

If the parts are not replaced then it is difficult to make a decision on what is or is not working.

I understand this however I was hoping that given what I have detailed so far perhaps someone with more knowledge and experience of how SMPSs work could give an idea as to why the fluctuating would occur when plugging into the mainboard and if it is possible to see if the PFC IC is working given those components not currently working.

[dick_barton]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Sorry but I had two power supply pdf's open at the same time and mixed them up so ignore the last post except for the comment that "if the parts are not replaced then it is difficult to make a decision on what is or is not working."

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Update:

I have replaced QB802 KD1691, ZD805 Z02W15VY and ICM801 MC33067. Attached updated PDF shows all parts replaced so far highlighted.

I now have the standby light on the front of the set ICM801 no longer gets hot.

When CNM801 is connected to the mainboard I only get ON/OFF - 3.94V, STBY - 5V, 5V - 5.29V, but no 13V or 24V. However, when it is connected they are on for 5 seconds the off for 5 seconds and this keeps cycling. The behavior is also exhibited for the voltages on ICM801.


With all cables disconnected from the PSU and when I connect ON/OFF and STBY with a 1KΩ resistor these voltages along with those on ICM801 hold steady.

Pressing the power button on the set had no effect when everything is connected.

I get 15.57V on the emmiter of QB802, thus IC_VCC to ICM801 and ICP801S sees to be the right voltage, correct?

I detached all cables from the PSU and connected ON/OFF and STBY with a 1KΩ resistor. The voltage on the main cap stays at 160V the same give or take when everything is plugged in normally.

Does this indicate that ICP801S FAN7530 is bad? Are there other things that could cause this behavior if ICP801S is bad? Are there other things I should be testing to be more conclusive? Are there other ways to test to see if ICP801S is working?

I am still not clear why the voltages cycle when CNM801 is plugged into the mainboard but not when I connect ON/OFF and STBY with the 1KΩ resistor. Would a bad PFC IC cause this or does this indicate a bad mainboard and is there anything that I can do to rule that possibility out?

The above all occurs without using the dim bulb tester.

Thank You Again

[budwich]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

my guess based on other attempts in these areas is to check the "conditions"/readings being fed the pfc especially control lines.... you may find that it is not being fully "turned on" / stable.

[dick_barton]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Disconnect mainboard from the PSU and connect ON/OFF and STBY with a 1KΩ resistor. Do exactly the same and connect PWR_ON/OFF to 5V using a 1K resistor and check the voltage across the main cap.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

my guess based on other attempts in these areas is to check the "conditions"/readings being fed the pfc especially control lines.... you may find that it is not being fully "turned on" / stable.

I flipped the PSU over and took readings from ICP801S FAN7530
1 1.029V
2 0V
3 increasing mV
4 0
5 0
6 GND
7 0
8 15.02V

Obviously not what these should be so I do not know if as you say what it is "fed" is the problem or that the PFC IC itself is bad? Based on the datasheet I think pin 1,2,4,5,8 are input and 3,7 are output but I am not certain.

Disconnect mainboard from the PSU and connect ON/OFF and STBY with a 1KΩ resistor. Do exactly the same and connect PWR_ON/OFF to 5V using a 1K resistor and check the voltage across the main cap.

I am not sure I understand. ON/OFF and PWR_ON/OFF are the same. The former is written that way on the actual board and the later on the schematic. If you mean to jump with a 5V from one of the pins 13-16, that only seems to be present when I jump the ON/OFF and STBY. Or did you mean do both?

[budm]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

So when you replaced the shorted out PFC MOSFET, you did not change the PFC IC at the same time? More than likely that the PFC is also damaged when the MOSFET shorted out.
BTW, the 'ON/OFF' label on the board is the same as BL-ON.
The ST-BY is the same as PS-ON.
Pictures provided by shojimmy.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

So when you replaced the shorted out PFC MOSFET, you did not change the PFC IC at the same time? More than likely that the PFC is also damaged when the MOSFET shorted out.
BTW, the 'ON/OFF' label on the board is the same as BL-ON.
The ST-BY is the same as PS-ON.

The PFC MOSFET is QP801S, correct? If so then yes I did not replace the PFC IC when that was replaced. If it is bad would this account for the behavior I have mentioned or the readings I get?

So that I may understand more fully, if the PFC IC is bad why does the cycling that I mentioned occur?

So then I did it correct by connecting the ON/OFF to STBY?

My most recent repair was on another Samsung PSU BN44-00264A which also uses the FAN7530. It was good and all that I replaced was the two MOSFETS and fuse and it worked so I was not thinking that this one would be bad. Perhaps the extent of the damage should have led me be more suspicious. I will have end up getting one from China if it is the culprit.

[budm]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

At this point, when you run the power supply board by itself WITHOUT any other board connected and you force on the ST-BY pin with resistor but you do not see the PFC Voltage and the 5.3V is steady, then you need to fix the PFC problem first, You may have more than one problem in your TV, but without working power supply then you are not going to get the correct action from the the TV.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Thanks for the additional information. I guess I need a new FAN7530 before we can go any further.

I know there is not much certainty in making further prognosis with out the PFC working, but knowing as much as everyone here does about LCD displays how often is the mainboard actually bad vs only a PSU problem.

I ask because my experience may bias what and average ratio actually is. If this one is fixed with the PSU repair then I have twice as many that have been fixed with only PSU repair than something else out of nine total.

Thank You

[budm]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

I wonder if the TV was hit by surges, I hope the main board will be OK, I would inspect the HDMI section to see if there is any sign of damages.

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

I hope the mainboard is good to after putting in the time and money so far. Is there anything in particular I should be looking for? Other than a visual inspection is there anything else at this point that can be done to verify that the mainboard is still good?

I have read of power surges coming back through the HDMI and damaging PSU and mainboards. Out of curiosity, because of this danger does anyone use or recommend the HDMI surge protectors that I have seen for sale?

Thanks

[Mad Capper]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Thought I would update the situation. I finally just received the PFC IC from China. I took a month to get here, about twice as long as my last purchase from there. Better late than never I guess.

I put it in and shorted the STBY and ON\OFF and got 400V. I plugged all connectors back in and it fired right up. All is well. Another one saved.

Thank you again to all who assisted me. I appreciate your time and willingness to help those of us who do not have the experience and knowledge you do.

[budm]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

Thanks for the follow-up on the repair.

[strs156]

Re: Samsung LN32A330J1D - BN44-00191B No secondary No Standby Sort of

I have a problem with a repaired same board .

It had a failure because of the brown glue shorting rm801 with qm801 and as a result RM801 WAS BURNED AND BOTH QM801 AND QM802 WAS SHORTED .
Also the transformer TM802 had one coil almost open because of the corrosion in one leg
I had to rewind the coils and properly solder the wire.
I replaced ICM801, RM801, QM801 ,QM802 and ZDTM801 KIA431A.
i have not replaced the pfc ic ICP801S (i am waiting to receive it).
The screen works ok for about 6-10 min and then starting to flashing the backlight (not one lamp but all of them at the same time.I measured the output voltage and it is 24 v when working ok and when the problem starts it drops to 22v .
The ICM801 gets really hot fast it must be over 90 celsius.
I tried the screen while pressing a heatsink on the chip and it was working fine for more than 20 mins.

My next thought is to replace every component on it .
Any ideas why this chip is getting too hot?