Samsung PS50C550 Voltage Drop Help

[moff13]

Hi there I have been looking on line for a while now and cant seem to find a similar instance of my problem. I have a black screen with sound. on power up the LED flashes 3 times and stays on at the 3rd flash. I have tested voltages VS and VA from the main supply with only the main board connected and all is good. Connect logic board ok supply cable Ok. VS_on high 3.3V.

When ever I connect the ribbon cable from the logic board to the Y sustain board Vs_on goes low and i loose all me voltages. This happens also when there is no supply to the Y Board i.e. power cable to y disconnected.

I have replaced the logic, the Y and the buffer board with no Joy? Is this a Power supply problem? If so where can I look as I cant really afford a new power board at the moment.

Thanks in advance

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

Can someone please help me with this?

[PlainBill]

Re: Samsung PS50C550 Voltage Drop Help

Can someone please help me with this?

You aren't giving much information to go on, and the information you are giving is contradictory. You say you have none of the voltages out of the power supply, but earlier you have sound. You can't have sound unless the power supply is working.

Here is the standard troubleshooting routine. Set up the TV with all cables connected. Turn on the TV. If it fails to turn on. go to step 2.

Step 1. Measure Vs, Va, Vset, Vscan, Ve, and the other outputs of the power supply. If any are missing, continue with step 2.

Step 2. Disconnect the power cord, disconnect the cable running from the power supply to the Z-Sustain board (right side as viewed from the back). Plug in the power cord, turn the TV on, and repeat measuring the voltages. If any are missing, go to step 3.

Step 3. Disconnect the power cord, reconnect the cable running from the power supply to the Z-Sustain board and disconnect the cable running from the power supply to the Y-Sustain board (left side as viewed from the back). Plug in the power cord, turn the TV on, and repeat measuring the voltages. If any are missing, go to step 4.

Step 4. Disconnect the power cord. Disconnect the cables running from the power supply to both sustain cards. Plug in the power cord and turn on the TV. Test for all voltages as above. Go to Step 5

Step 5. Diagnosis: If any voltage is missing while both sustains are disconnected, the power supply is defective. If any voltage is missing when either sustain is connected, the power supply is defective. If a voltage drops out only while a particular sustain is connected, that sustain is defective.

PlainBill

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

Cheers PlainBill for you reply. Sorry I was not so clear this is my first post. I will try and make it a bit clearer. My suppy board is numbered BN44-00330B Scematic attached. On this board there are three connector termanals. None Supply Vscan or Ve so I presume they are generated on the Y board and Z Board respectively.

Connector CN804 feeds the y board and the Y board appears to feed the Z board so disconnecting this cable I disconnect power to both Y and Z boards.

Connector Cn801 connects to the Main board which I have left connected throughout testing hence the sound.

Connector CN802 connects to the logic board where i measure VS_ON.

1) With only CN801 connected voltages VS, VA, and VG all Good

2) Add connector CN802 and no other cables to logic, voltages VS, VA, and VG all Good plus Vs_on high 3.3V

3) Connected ribbion cable from Y Sus to logic VS_on goes low and voltages VS, VA, and VG fall to 0V.

4) Swapped Y board and logic same problems.


On further inspection under the microscope it appears ICC401 micro on the power board appears to have small pinhole crater. The part number MCV14A-I/SL is difficult to find but have found part PIC16F526-I/SL which appears to be almost identical. Have ordered some chips and will inform you if this fixes the issue.

[PlainBill]

Re: Samsung PS50C550 Voltage Drop Help

The light dawns!!! This is built for the PAL market. You are right, they are radically different than we see on this side of the pond. That, by the way, is one of the reasons we encourage people to update their profile with their location. That might have saved me the trouble of making a fool of myself. (Not that this is the first time.) Lot's of luck on the IC; unless you were able to buy it programmed with Samsung's code (or ahve access to the code and a programmer), it won't work.

PlainBill

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

Thanks again. I though it would be an easy swap. Wasn't aware it needed special Samsung coding. Will have to save my pennies for a new Power Board then.

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

Hi Bill,

Still puzzled. Seems I wasted some more of my hard earned cash on a power board which did not rectify the problem.

To Recap I have a pal system where VS and Va are generated on the supply board. Vscan and Ve appear to be generated on the Y and X respectively however these are not connected to the power board.

I have attached a simple flow chart of what I have and hope it helps.

Basically the tv powers on with VS and Va correct (High) when the LVDS cable is not connected to the y sus.

Connecting the LVDS cable the VS and VA start high and fall gradually to zero when powered on and appears the VS_ON from logic to power goes low.

I have swapped out the power board, the logic and the Y still no joy? Bambozelled?

The logic LED also goes from a 1 hertz flash on off (no LVDS connection) to 5/6sec on 1 sec off when Connected.

This happens when there is no power to the y and when the y is powered.

Thanks in advance

[PlainBill]

Re: Samsung PS50C550 Voltage Drop Help

Sorry, I can't be of much help. Plasma sets for the PAL market are radically different than those for the North American market. I saw pictures of a recent LG Plasma set, and radical changes have been made from those I am familiar with. Without a service manual or troubleshooting guide I am lost.

PlainBill

[PowerAmpFreak]

Re: Samsung PS50C550 Voltage Drop Help

Hi Bill,

Still puzzled. Seems I wasted some more of my hard earned cash on a power board which did not rectify the problem.

To Recap I have a pal system where VS and Va are generated on the supply board. Vscan and Ve appear to be generated on the Y and X respectively however these are not connected to the power board.

I have attached a simple flow chart of what I have and hope it helps.

Basically the tv powers on with VS and Va correct (High) when the LVDS cable is not connected to the y sus.

Connecting the LVDS cable the VS and VA start high and fall gradually to zero when powered on and appears the VS_ON from logic to power goes low.

I have swapped out the power board, the logic and the Y still no joy? Bambozelled?

The logic LED also goes from a 1 hertz flash on off (no LVDS connection) to 5/6sec on 1 sec off when Connected.

This happens when there is no power to the y and when the y is powered.

Thanks in advance

So, basically you swapped all the boards but not the mainboard then?

[PowerAmpFreak]

Re: Samsung PS50C550 Voltage Drop Help

Thanks again. I though it would be an easy swap. Wasn't aware it needed special Samsung coding. Will have to save my pennies for a new Power Board then.

The PIC is a microcontroller that needs a firmware to run. If you buy this from a local store it will be empty. So it has to be programmed by the correct code.
This usually means the board is unrepairable, since getting the correct code into the new PIC will be considered impossible most of the time.
Obviously the PIC wasn't the problem in your case anyway.

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

So, basically you swapped all the boards but not the mainboard then?

Yes thanks for your response. I have swapped out all the boards but not the main. I didn't believe the main to be the problem as the voltages only drop when the LVDA cable from the logic is connected to the Y sustain.

This happens when no ribbon connectors are connected to the main.

[moff13]

Re: Samsung PS50C550 Voltage Drop Help

The PIC is a microcontroller that needs a firmware to run. If you buy this from a local store it will be empty. So it has to be programmed by the correct code.
This usually means the board is unrepairable, since getting the correct code into the new PIC will be considered impossible most of the time.
Obviously the PIC wasn't the problem in your case anyway.

Yes correct swapping with a new power board did not correct the problem?

[msarfraz]

Re: Samsung PS50C550 Voltage Drop Help

hey bud....were you able to fix your problem......i have the same issue....when i connect the ribbon cable from logic board to the y sus the voltages drop.
If you did manage to fix...what was the problem?

[Bling23]

Re: Samsung PS50C550 Voltage Drop Help

Has anyone fixed this problem?? I have the same problem on a RCA 42PA30RQ

[Bling23]

Re: Samsung PS50C550 Voltage Drop Help

My TV set is NTSC

[smason]

Re: Samsung PS50C550 Voltage Drop Help

Has anyone fixed this problem?? I have the same problem on a RCA 42PA30RQ

You should really start a new thread with RCA 42PA30RQ in the subject.
I really doubt your RCA is the same as the Samsung in this thread

[mali67]

Re: Samsung PS50C550 Voltage Drop Help

did you ever sort this? i have the same problem

[tw2005]

Re: Samsung PS50C550 Voltage Drop Help

did you ever sort this? i have the same problem

I don't think he'll be watching, nil posts since 2011.

Maybe start a fresh post with a full description of thesymptoms and some pictures of the layout and boards,

My gut feeling if it's the same as above will be faulty Xmain,Ymain and or buffers.

The last Samsung I touched was a 2010 42", similar setup and it was tricky as the xmain can damage the ymain too.

Most people suggest doing all those at once rather than risk having a bad board damage another.

I gave up trying to repair the xmain but by the time I'd finished the ymain ended up shorted too.

So I replaced the lot and did the firmware upgrade as I think that one had issues with the firmware.

Tv worked after that, buffer boards ended up ok in the end but Y & x were no good.

There are some panel tests you can try with the control board isolated from the main.

If the TV had a display doing this then that would point to a bad main board. I don't know the procedure for this, someone else here will though.

[mali67]

Re: Samsung PS50C550 Voltage Drop Help

I don't think he'll be watching, nil posts since 2011.

Maybe start a fresh post with a full description of thesymptoms and some pictures of the layout and boards,

My gut feeling if it's the same as above will be faulty Xmain,Ymain and or buffers.

The last Samsung I touched was a 2010 42", similar setup and it was tricky as the xmain can damage the ymain too.

Most people suggest doing all those at once rather than risk having a bad board damage another.

I gave up trying to repair the xmain but by the time I'd finished the ymain ended up shorted too.

So I replaced the lot and did the firmware upgrade as I think that one had issues with the firmware.

Tv worked after that, buffer boards ended up ok in the end but Y & x were no good.

There are some panel tests you can try with the control board isolated from the main.

If the TV had a display doing this then that would point to a bad main board. I don't know the procedure for this, someone else here will though.

i was going to post a new post, but the OP has described it way better than i could, with the identical problem

[tw2005]

Re: Samsung PS50C550 Voltage Drop Help

i was going to post a new post, but the OP has described it way better than i could, with the identical problem

Maybe something in this , covers models with the same boards as yours