Samsung BN44-00289B Power Board troubleshooting

[Jaze]

Re: Samsung BN44-00289B Power Board troubleshooting

BD901 is basically an inductor, I don't think I have ever seen one of these go open. Replace it with a 1Ω 1/2w or maybe a 2~3 amp fuse for testing

Ok So I replaced it with the 1Ohm resistor and now I am getting full voltage to capacitor CI890.

What I am noticing now is that the voltages are starting off high and gradually dropping.

When checked QI 820 & QI821 voltages, I am getting

Gate 3V and dropping

Collector to emitter 240V and dropping

The TI801S is receiving 240V then dropping off to 2V. The resistance on the secondary of the TI801S is 1Kohm on each.

Can you advise on what is the incoming voltage required on DT801S? Should it be 12V each from QI802/QI803 & from QI805/806?

Not seeing any issues with the components around QI820 and QI821.Checked the inverter secondary yesterday and didn't find anything either. Any other checks?

[dick_barton]

Re: Samsung BN44-00289B Power Board troubleshooting

The voltage on the transformer TI 801S will be an high frequency AC voltage.
Check your fuse FM802S for continuity
What dc voltage do you have between the two legs of CP815

Zeners ohm - reverse
ZD801 685 - /
ZD803 730 - /
ZD804 300 - 710
ZD804 725 - / (note R climbed tho like a cap)

Were these measured while still attached to the board.
I would lift ZD804 and test out of circuit. It's a 10V 1 watt Zener.

[dick_barton]

Re: Samsung BN44-00289B Power Board troubleshooting

Just came across this thread which you could follow

https://www.badcaps.net/forum/showth...e32b350&page=2

I think i found three shorted diodes. (zd804, dm852, zm804) I ordered the parts and will hope that will fix it.

and it was a fix.

[nomoresonys]

Re: Samsung BN44-00289B Power Board troubleshooting

Easy way to test Zd804 out of circuit, just clip one of the legs above the board and test it, just be sure you have enough room to solder it back together, meaning not too close to either end of the leg so in the middle is good, middle of one of the legs that is.

[Jaze]

Re: Samsung BN44-00289B Power Board troubleshooting

Hi. Those results were from the previous user, not my question. Right now I am getting the Det5v output and the voltages stabilized. But when I connect it to the tv board, it is dropping off. Does this mean a bad tv board now?

[nomoresonys]

Re: Samsung BN44-00289B Power Board troubleshooting

Exactly why people should start their own threads...to avoid that.

[dick_barton]

Re: Samsung BN44-00289B Power Board troubleshooting

I didn't notice the changeover, however you mention

Also I got a Zener diode ZM804 giving continuity.

Have you checked it out of circuit or replaced it?

I have opened up the television and disconnected the power board. These are the readings I am getting.

Harness CN802
PINS ------ MEASURED VALUES
PWR ON/OFF ----- 0.783V
STBY5.3V ------ 5.3V
GND ------ GND
13V ------ 12.88V
GND ------- GND
GND ------ GND
5.3V ----- 5.3V
5.3V ------ 5.3V
GND ------ GND
13V ------ 12.88V
13V ------ 12.88V
INVERTER ON/OFF ------ 2.89V
E-PWM ------ 4.95V
DET_5V ------- 0V
SYNC ------ 0V
GND ------ GND

PWR On/Off is connected to 5.3V via RM882 so it should not be missing?

[nomoresonys]

Re: Samsung BN44-00289B Power Board troubleshooting

I didn't ether Dick, wouldn't have commented on JLancer's thread if I knew it was idle for 18 months.

[Jaze]

Re: Samsung BN44-00289B Power Board troubleshooting

I didn't notice the changeover, however you mention

Have you checked it out of circuit or replaced it?




PWR On/Off is connected to 5.3V via RM882 so it should not be missing?

Ended up replacing it but was good when taken out and checked. Hmm. So the 0.78V is too low for the power?