Samsung PN43D450A2D

[crashp3]

First off, thanks in advance for any help or input you can provide!

I am working with a Samsung Plasma PN43D450A2D, which was given to me by a friend. One night he was hit with a surge that took out this TV, the Comcast STB connected to it (via HDMI), and 2 other Comcast boxes in the home - a pretty bad surge!

The TV has no sign of life (red indicator, etc.). With the back removed, I could hear a humming/clicking coming from the power supply - on a hunch I purchased a new power supply/board, however that did not correct the problem. When applying AC power, it will still make the humming/clicking noise, but that's it.

I'm defintely a novice when it comes to TVs, and I was unable to find a wiring schematic or any information for repairing this TV.

For reference in the pics, SUS1 is the main SUS that is connected to the power supply. From there, SUS1 daisy chains to SUS2 to provide power to that SUS. There is no direct connection from SUS2 to the power.

Sorry, I know they are considered YSUS and XSUS, but I honestly don't know what that means or which is which


I'm pretty handy with a multimeter, and my father is very good with them and basic electronics repair, so I can troubleshoot whatever is required. Additional/more detailed pictures can be taken if needed

note: I know on the mainboard a few connectors are disconnected - I did that during troubleshooting (making sure all were tight) and didn't reconnect prior to this picture.

Any assistance will be greatly appreciated!!

[tom66]

Re: Samsung PN43D450A2D

Does a clicking sound come from here?

A common issue is unrelated to surge damage. The two transistors under the large heatsink on the power supply can get cold solder joints.

[crashp3]

Re: Samsung PN43D450A2D

Thanks for the reply, Tom.

I listened to both the new power supply, and the one that I presumed was defective. The component making the buzzing noise (on both of them) is the white transformer marked in the picture.

This transformer will only make the noise when the AV "input board" is connected to the PSU. The noise isn't present when any other components and/or none are connected to the PSU.

[tom66]

Re: Samsung PN43D450A2D

That's the standby transformer. Buzzing can come from some transformers if they are working.

Do you have a digital multimeter?

[crashp3]

Re: Samsung PN43D450A2D

I do - here is pictures of the DMM I have - from reading, I know you all like pictures

If this one isn't sufficient, I can swing by a store and pickup one based on your recommendation.

[tom66]

Re: Samsung PN43D450A2D

That's a good multimeter, no need to get a new one.

Can you post a closer picture of the connector going from the power supply to the main board - there are some labels next to it which indicate what pin does what.

[crashp3]

Re: Samsung PN43D450A2D

Glad to hear it's a decent DMM - Craftsman quality has seemed to go down in years.

Attached are (3) pictures.

CN801 -> Connector to the "av input" board
CN802 -> Connector to the board labeled "main board" in my original post (2nd picture)
CN804 -> Connector to SUS1


CN801 didn't turn out very clear, so here is the pinheader silk-screen information, going from left (pin1) to right:

1- PS-ON
2- STBY
3- GND
4- D15V
5- GND
6- GND
7- D5.3v
8- D5.3v
9-GND
10-D15V
11-D15V
12- D5.3v

Please let me know if the pictures aren't clear enough. It's overcast today and getting good macro shots is tough without good sunlight - for me atleast.

[tom66]

Re: Samsung PN43D450A2D

Okay, check the STBY pin.

- Multimeter on DC 20V
- Black probe in frame of TV (spare screw hole, wall bracket, etc.)
- Red probe on metal part of STBY pin

Voltage should be around 5V.

[crashp3]

Re: Samsung PN43D450A2D

STBY pin measured 5.32v with all other connectors (mainboard.sustain) still plugged in.

[tom66]

Re: Samsung PN43D450A2D

STBY pin measured 5.32v with all other connectors (mainboard.sustain) still plugged in.

Okay now check the pins marked PS-ON, D5.3V and D15V using the same procedure.

If PS-ON is around 3V or 5V, but the D5.3V or D15V lines are low, it is a problem with the PSU.

If PS-ON is stuck low, it is a problem with the main board or PDP t-con board.

[crashp3]

Re: Samsung PN43D450A2D

Thanks again for the help.

I tested PS-ON for both my old and "new" power supply. For the "new", it measured 3.7v and the old measured 3.67v.

Unfortunately for both of the power supplies, all other pins (D5.3 and D15) measured NO voltage at all.

To note, the test procedure was performed with all other components connected to the power board. Based on reading this forum, I also put black probe to chassis ground and red probe to the VS-TP test point - this also produced a 0vdc reading.

Not sure if it's bad luck to have (2) bad power supplies... or that I'm doing something wrong.

[crashp3]

Re: Samsung PN43D450A2D

Just to satisfy curiosity, I disconnected all components from the powerboard and performed the same test. PS-ON and STBY produced the same voltage, all other pins were still dead.

[tom66]

Re: Samsung PN43D450A2D

Remember, these PSUs are pulls from dead, smashed screen TVs. Usually damaged/dropped in shipping. Any number of faults could be present on the PSU board you got.

Does the TV power on if the main board is plugged in but the PDP T-con is disconnected? (The PDP T-con is the small board which interfaces with the main, Y sustain and Z sustain boards, as well as the X buffers.)

[crashp3]

Re: Samsung PN43D450A2D

No power with the PDP T-con disconnected. No voltage across the pins above, either.

[tom66]

Re: Samsung PN43D450A2D

Just as a final test to try and confirm whether it is the PSU or main/t-con board do you have or can you acquire a 1k ohm resistor? This is to test if the PSU has a active-low turn on signal.

[PowerAmpFreak]

Re: Samsung PN43D450A2D

Often, the PS-ON signal on Samsung PSU's are active low.

[tom66]

Re: Samsung PN43D450A2D

Often, the PS-ON signal on Samsung PSU's are active low.

Then it should be called PS-OFF.

[crashp3]

Re: Samsung PN43D450A2D

I do have 1kohm resistors

[tom66]

Re: Samsung PN43D450A2D

Great; can you wire one from PS-ON to GND. Check PS-ON voltage now, should be close to 0V. If it is more than 0.5V try reducing the resistance to 100 ohms or so.

If the D5.3V/D15V rails then come up then the problem is on the main or t-con.

[crashp3]

Re: Samsung PN43D450A2D

Alright - jumpered it with a 100ohm resistor, which brought PS-ON to ~.3volt. From there (with all other boards disconnected from the power supply), all pins on CN801 outputted the proper voltage!

I'm assuming this means the power supply is good!

Am I able to leave the jumper in place, plug in the SUS boards and T-CON board and see what happens - or is that unsafe to do so?

Thanks again for the advice...!

note for any future readers: 1k OHM resistor had PS-ON at .7 volts, and CN801 would not output voltage - only until the 100ohm resistor was used did the power supply "turn on".