Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

[jczarniak]

Hi,
TV is starting up (I can hear the startup melody).
Backlight and sound from HDMI source are present for 1-2 seconds and TV reboots.
I checked the voltages on power supply.
Everything looks OK except 13 V line.
I see only 12.5 V dropping to 12.1 when TV is starting.
I need your help guys to help me find the fault / faulty parts on the power supply.
I cant find anything obvious.
Thanks a lot.

[budm]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

That 13V is not tightly regulated supply.
What are the DCV reading on those pins of the connector of the power supply board that goes to the main board when TV is OFF and when power switch is activated?
You MUST report the reading in this format:
Pin NAME ????, DCV = ????

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

That 13V is not tightly regulated supply.
What are the DCV reading on those pins of the connector of the power supply board that goes to the main board when TV is OFF and when power switch is activated?
You MUST report the reading in this format:
Pin NAME ????, DCV = ????

So, CN802, cable between main board and PSU unplugged:
PIN 1 - 12.64 V
PIN 2 - 5.28 V
PIN 3 - 12.64 V
PIN 4 - 5.28 V
PIN 5 - 12.64 V
PIN 6 - 5.28 V
PIN 7 - 0
PIN 8 - 0
PIN 9 - 0
PIN 10 - 0
PIN 11 - 5.28 V
PIN 12 - 0
PIN 13 - 5.28 V
PIN 14 - 5.28 V
PIN 15 - 12.64 V
PIN 16 - 5.28 V
PIN 17 - 12.64 V
PIN 18 - 0.78 V

CN802, cable between main board and PSU connected, TV on:
PIN 1 - 12.28 - 12.45
PIN 2 - 4.82 - 5.24
PIN 3 - 12.28 - 12.45
PIN 4 - 4.82 - 5.24
PIN 5 - 12.28 - 12.45
PIN 6 - 4.82 - 5.24
PIN 7 - 0
PIN 8 - 0
PIN 9 - 0
PIN 10 - 0
PIN 11 - 4.82 - 5.24
PIN 12 - 0
PIN 13 - 4.82 - 5.24
PIN 14 - 4.82 - 5.24
PIN 15 - 12.28 - 12.45
PIN 16 - 4.82 - 5.24
PIN 17 - 12.28 - 12.45
PIN 18 - 0.64- 0.72 V

Thanks.

[vinceroger69]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

So, CN802, cable between main board and PSU unplugged:
PIN 1 - 12.64 V
PIN 2 - 5.28 V
PIN 3 - 12.64 V
PIN 4 - 5.28 V
PIN 5 - 12.64 V
PIN 6 - 5.28 V
PIN 7 - 0
PIN 8 - 0
PIN 9 - 0
PIN 10 - 0
PIN 11 - 5.28 V
PIN 12 - 0
PIN 13 - 5.28 V
PIN 14 - 5.28 V
PIN 15 - 12.64 V
PIN 16 - 5.28 V
PIN 17 - 12.64 V
PIN 18 - 0.78 V

CN802, cable between main board and PSU connected, TV on:
PIN 1 - 12.28 - 12.45
PIN 2 - 4.82 - 5.24
PIN 3 - 12.28 - 12.45
PIN 4 - 4.82 - 5.24
PIN 5 - 12.28 - 12.45
PIN 6 - 4.82 - 5.24
PIN 7 - 0
PIN 8 - 0
PIN 9 - 0
PIN 10 - 0
PIN 11 - 4.82 - 5.24
PIN 12 - 0
PIN 13 - 4.82 - 5.24
PIN 14 - 4.82 - 5.24
PIN 15 - 12.28 - 12.45
PIN 16 - 4.82 - 5.24
PIN 17 - 12.28 - 12.45
PIN 18 - 0.64- 0.72 V

Thanks.

can you edit this with the pin names ie ps on bl on 5v 12v etc

[budm]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Where are the pin names? Those numbers do not mean anything without the pin names to tell use what those pins are for.

"You MUST report the reading in this format:
Pin NAME ????, DCV = ????"

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Where are the pin names? Those numbers do not mean anything without the pin names to tell use what those pins are for.

"You MUST report the reading in this format:
Pin NAME ????, DCV = ????"

Sorry, very busy at the moment.
I'll change the format tomorrow.
See the pin names on the picture attached.
Thank you.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Sorry, very busy at the moment.
I'll change the format tomorrow.
See the pin names on the picture attached.
Thank you.

Hopefully that is more clear now.
Thanks.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Where are the pin names? Those numbers do not mean anything without the pin names to tell use what those pins are for.

"You MUST report the reading in this format:
Pin NAME ????, DCV = ????"

Hopefully that is more clear now.
Thanks.

[vinceroger69]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

ps on pin seems very low? with mainboard connected or unplugged maybe worth forcing on just the psu do all the voltages stay stable and not drop out.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

ps on pin seems very low? with mainboard connected or unplugged maybe worth forcing on just the psu do all the voltages stay stable and not drop out.

I tried that.
I made the bridge between PS_ON and A5V.
All voltages going up by about 0.1 - 0.15 Volt but TV still behaves in the same way

[vinceroger69]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

without the mainboard connect at all? just the psu as we need to rule out the psu first.
so does the psu still power cycle on and off with no mainboard connected just ps on connected to 5v through 1k resistors

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

without the mainboard connect at all? just the psu as we need to rule out the psu first.
so does the psu still power cycle on and off with no mainboard connected just ps on connected to 5v through 1k resistors

When main board is disconnected, PSU is NOT in the power on/off cycle.
With the bridge, voltages are stable and higher by about 0.1 - 0.15 Volt.

Don't remember now how it looks like with cable connected to main board.
I'll check that today.

I didn't use 1k resistor to bridge the PS_ON and A5V. Is this making any difference, please?

[vinceroger69]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

possible mainboard or backlight led faiure hopefully a more experienced member can advise you more.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

possible mainboard or backlight led faiure hopefully a more experienced member can advise you more.

Hopefully.
Thank you very much anyway.

[dick_barton]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

I didn't use 1k resistor to bridge the PS_ON and A5V. Is this making any difference, please?

It is always safer to use a resistor when jumping pins.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

It is always safer to use a resistor when jumping pins.

OK, good to know.
Thank you.

[dick_barton]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Backlights should be on when powering up without the main board connected.

PS_ON requires 3V> so if it's falling when connected to the mainboard then it would look like you have a mainboard problem.

Try heat/cool the EEprom on the main board.

[ReeceyBurger123]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

possible mainboard or backlight led faiure hopefully a more experienced member can advise you more.

Not an Led set buddy, inverter is on the psu

[vinceroger69]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Not an Led set buddy, inverter is on the psu

i agree lol just looked at the psu picture.

[jczarniak]

Re: Samsung LE46C750, power supply BN44-00341A - LOW VOLTAGES

Backlights should be on when powering up without the main board connected.

PS_ON requires 3V> so if it's falling when connected to the mainboard then it would look like you have a mainboard problem.

Try heat/cool the EEprom on the main board.

What I noticed yesterday:
- PSU was unplugged / disconnected for whole night. Checked the voltages with only power cable plugged in and there was 13 Volt on the correct pins, 13.2 with bridge on PSU_ON
- connected the backlight, stil 13 Volt, no backlight
- connected the main board, 12.4 V, no backlight
- disconnected the main board, 12.6 V, backlight ON
- 13 volt didn't came back
- backlight connected, main board disconnected, 12.6 V, backlight ON