Samsung LE27T51BX/BWT no start

[rafis]

SUMMARY
======
Samsung LE27T51BX/BWT
CPU: FLI5921H-LF
Panel: V270B1-L01 rev c1
T-con: V270B1-L01
Inverter (backlight): DARFON V070 4H.V0708.001 /E5 OZ960GN, LM339, 4006A, FDS8958A

THINGS TESTED
==========
Had trickling at start. STB voltage was 16V
After replacing Power board components no start, red LED, all voltages on the exit connectors of the power board are tested and OK
Parts replaced: CM852, 851, 856, 860, 861
CS804,
IPS801S
DZS801, DZS802, DZ803

With Main board disconnected backlight is still off. No image on panel (bulb test).

PROBLEM
======
1. Power LED is on at plug in.
2. Pressing power button makes LED blink 3 times
3. Short P is heared from dynamics and led is switched off

QUESTION
=======
How to troubleshoot further?


Manual

Power board

[dskall]

Re: Samsung LE27T51BX/BWT no start

Need voltages from connector that goes from power supply board to main board. Will need pin#- PIN DESCRIPTION -Pin voltage in standby-Pin voltage when pushing power button and picture of connector on power supply board.
Format:
Pin# - Pin Description - Pin Voltage standby - Pin voltage power on
1 - XXXXXXX - XXv - XXXv
2 - XXXXXXX - XXXv - XXXv
3 - XXXXXXX - XXXv - XXXv
4 - etc.

[rafis]

Re: Samsung LE27T51BX/BWT no start

Pin# - Pin Description - Pin Voltage standby - Pin voltage power on
1 - POWER_ON/OFF - 0v - 2,9v
2 - ST/BY_6.2V - 6,66v - 6,12v
3 - GND - 0v - 0v
4 - GND - 0v - 0v
5 - GND - 0v - 0v
6 - 12V - 0v - 12,08v
7 - 12V - 0v - 12,08v
8 - 12V - 0v - 12,08v
9 - GND - 0v - 0v
10 - GND - 0v - 0v
11 - GND - 0v - 0v
12 - 5,4V - 0,2v - 5,39v
13 - 5,4V - 0,2v - 5,39v
14 - 5,4V - 0,2v - 5,39v
15 - GND - 0v - 0v
16 - 12V - 0,05v - 13,21v

[dskall]

Re: Samsung LE27T51BX/BWT no start

Do you get image on screen with flashlight pressing menu? Are you getting 24v to inverter, bl_on signal probably on inverter board

[rafis]

Re: Samsung LE27T51BX/BWT no start

image - no
24v - yes
bl_on signal is coming but not constantly

[rafis]

Re: Samsung LE27T51BX/BWT no start

BL ON/OFF - 5,2V constant
P/D - 4,9V

Also noticed light "shsh" in the speakers during 15 sec after switching on, then LED switches of. If Power button is pressed, it goes to the S/B mode (LED is on), if pressed again - starts to blink as on startup and everything repeates again

[dskall]

Re: Samsung LE27T51BX/BWT no start

You seem to have your voltages. Maybe a firmware problem. You could try freezing eeprom to see if it will turn on

[rafis]

Re: Samsung LE27T51BX/BWT no start

You seem to have your voltages. Maybe a firmware problem. You could try freezing eeprom to see if it will turn on

How do I freeze eeprom?

[dskall]

Re: Samsung LE27T51BX/BWT no start

You can use freeze spray or can of air duster upside down. Spray on eeprom several times then try to power on. It is probably 8 pin chip next to main processor with 24 or 25 in it's number.

[dick_barton]

Re: Samsung LE27T51BX/BWT no start

What are the label names and voltages at the connector in red box?

Have you checked the fuse on the inverter board "F4"

[rafis]

Re: Samsung LE27T51BX/BWT no start

What are the label names and voltages at the connector in red box?

Have you checked the fuse on the inverter board "F4"

1 BL ON/OFF 5,27
2 A/D 3,25
3 P/D 4,94
4 GRD 0
5 24V DET 5,22

Yes, I have checked the fuse on the inverter board. But I'm not sure if I should desolder it. It shows 2 MOhm and goes down. In continuity meashurement node it shows short first half a second.

[dskall]

Re: Samsung LE27T51BX/BWT no start

If you are testing fuse it would either be open or short

[rafis]

Re: Samsung LE27T51BX/BWT no start

If you are testing fuse it would either be open or short

It's short first second then opens.

[vinceroger69]

Re: Samsung LE27T51BX/BWT no start

power on the set and test the dc voltage to each side of the fuse black probe on metal tv chassis or grounding screw

[rafis]

Re: Samsung LE27T51BX/BWT no start

One side is constant 24V, other side is growing from 16V to 22,5V during 30 seconds, then ranges 22,4-22,7V. This is for F4 and F2. Also meashured F1 and F3 one side is 1.4V and another 24V

[dick_barton]

Re: Samsung LE27T51BX/BWT no start

With the power ON the voltages measured on each side of any fuse should be identical otherwise they are faulty.

With the power OFF put your meter on ohms range and with the set off place your meter probes across each fuse and it measure 0 ohms are close to 0 ohms

[rafis]

Re: Samsung LE27T51BX/BWT no start

In ohms range all four have open loop.
What should I check to prevent repeated fuse blow?

[vinceroger69]

Re: Samsung LE27T51BX/BWT no start

if all four fuses have blown you could end up replacing a lot of parts as invertor boards are so cheap i would just purchase a new one.

[dick_barton]

Re: Samsung LE27T51BX/BWT no start

That sounds a bit drastic that all 4 fuses are open circuit. Can you double check by shorting your two probes together which should show 0 ohms or close to it and then check the fuses again which should show 0 ohms or again close to it.

I'd agree with Vinceroger69 that if they are all open then it would be best to replace the board.

[dskall]

Re: Samsung LE27T51BX/BWT no start

You might remove fuses and check out of circuit