another bn44-*****

[merkin]

specifically bn44-00267b in a sammy ln52b530p7fxza

history:
two years ago the tv would not turn on. when you turned on the power, the red stdby indicator light would go from solid to flashing a couple of times and then back to solid.

i pulled the power supply board and replaced the following caps:
cp814
cp8?? (next to dm801)
cm807
cm808
cm811
cm818
cm819
cm820
(i think that was it)

problem was fixed..

present time:
issue has returned, but at this time its intermittent. sometimes the tv will power on and sometimes it will not. when it does power on, after a while the picture will go black (off automatically) and the stdby indicator light will come on, and then after some time the tv will automatically come back on.

here is the psu:
http://www.shopjimmy.com/samsung-bn4...upply-unit.htm

would like to get to the root of the issue this time around. got scopes, meters and other test equipment at my disposal, but need some insight on what to test.

[CapLeaker]

Re: another bn44-*****

heat up the caps with a hair dryer and see if the tv turns on without hickups.
check the BLon pin and see if you loose voltage (when the backlights turn off).

[merkin]

Re: another bn44-*****

thanks ill try when i get home from work tonight.

any insight on theory behind the tests you want me to run?

also i see a lot of schematics posted for bn44 psu types, but not one specific to mine..if anyone has the bn44-00267b schematic please share. thanks.

[R_J]

Re: another bn44-*****

I would check the board for poor solder connections, mostly the transistors etc.that are attached to heatsinks, look at them with some magnification or just resoler them.

[CapLeaker]

Re: another bn44-*****

My theory? If it is a capacitor problem, the tv should work fine one the caps are warm, as it lowers the ESR.
BLon is generated on the main board. If you lose BLon, the backlights go out. If you don't lose BLon, look at the inverters. But we didn't get that far yet. RJ has also a valid point to check for cold solder joints.

[merkin]

Re: another bn44-*****

after removing and re-connecting the psu, i plugged in the tv and turned it on. its been on for almost 24 hours.

what pin on cn801 is the BLon pin?

[kevinm34232]

Re: another bn44-*****

What is the main board part #?

[merkin]

Re: another bn44-*****

What is the main board part #?

cant check now, but its an input on the psu anyway..see cn801 from the link in the first post. pin23 maybe?

[kevinm34232]

Re: another bn44-*****

Well it sounds like you are not just losing the backlight but the TV actually shuts off?

[CapLeaker]

Re: another bn44-*****

BLon comes from the mainboard and it turns the backlights on. So verify that it is still present when the backlights are out. I don't know exactly what pin it is, because I can't zoom the pic good enough to read it.

Also check the PSon pin. That also comes from the main board.

[merkin]

Re: another bn44-*****

are you clicking on the photo in the link?
its hi-res.. you can zoom in and see the pinout.

[kevinm34232]

Re: another bn44-*****

cant check now, but its an input on the psu anyway..see cn801 from the link in the first post. pin23 maybe?

My point is if the TV is not coming on, standby light flashing, eventually turning on, you may have a main board problem if your part # is the same as the one below or similar, very common issue.

http://www.ebay.com/itm/131529336351

[CapLeaker]

Re: another bn44-*****

are you clicking on the photo in the link?
its hi-res.. you can zoom in and see the pinout.

My tablet won't let me.

[merkin]

Re: another bn44-*****

1. PS
2. sync
3. SB
4-6. GND
7,8. 13V
9-12. GND
13-16. 5.1V
17,18,20. GND
19,21,22. 13V
23. INV-ON
24. I-PWM
25. E-PWM
26. GND
27. 5V_DET
28-30. GND

[CapLeaker]

Re: another bn44-*****

PS = PSon, INV-on=BLon
See what happens to all those pins when the TV is working fine and again when it failed. Use pin out name and the voltages measured.