Samsung LA40C530F1R Backlight goes off/ 5v detect drops

[EDE]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

I will check today. And get back to you soonest.

What was strange is the TV came on for a minute then shut down again after trying to clean main board.

[EDE]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

I will check today and get back to you.

[EDE]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Hi Budm,
Ok, it makes sense. I will check today and get back to you. I actually measured the wrong board(PS).
Apologies.

[EDE]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Hi Budm.
I measured Pin 2 DET on main board 21.9kohm (isolted from PS Board)

and when connected Main to PS = 7.5Kohm@ pin2 DET

[nomoresonys]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Looks like the mainboard isn't sending the ps-on signal properly.

[EDE]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Hi thanks for your input.....
I tried cleaning Main board with isopropyl alcohol and tv is on now! Weird! is this then due to flux on board?

[budm]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

So now 5V_DET is high now?

[nomoresonys]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

"18. PS_ON 0.7V" then you must have read it wrong, don't see how the powerboard comes on if this never goes higher than .7v.

[budm]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

1. B13V 12.2V
2. 5V_DET 3.4V
3. B13V 12.2V
4. BLU_ON 5.2V
5. B13V 12.2V
6. E-PWM 3.8V
7. GND 0.0V
8. H_SYNC 1.8V
9. GND 0.0V
10. GND 0.0V
11. B5V 5.2V
12. GND 0.0V
13. B5V 5.2V
14. B5V 5.2V
15. B13V 12.2V
16. A5V 5.2V
17. B13V 12.2V
18. PS_ON 0.7V
That my be typo but since all the switched power supply Voltages are present and probably the PFC Boosted Voltage too are present which means the PS-ON control signal is good enough to turn on all those switched Voltages.

[nomoresonys]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Indeed.

[Bhekifa]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

Hi Vince, thanks, quite right, one of the lamps turned out to be faulty. The other lamps also look blackened at the tips. Can the lamps be bought loose? I took one out of a scrapped panel and managed to get the lamps running. (photos)

Thanks again input from Budm & tvtimmy as well

Hi
Was you tv fixed after that because mine is giving me the same problem

[nomoresonys]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

These models are pretty easy to test compared to some others, not exact same models there but gives you the gist of testing: https://www.youtube.com/watch?v=oE6K4xBVweA https://www.youtube.com/watch?v=Dh01ZepjDp0 https://www.youtube.com/watch?v=lvBo3vetuGs

[nomoresonys]

Re: Samsung LA40C530F1R Backlight goes off/ 5v detect drops

I believe there's a nifty little lamp bypass in one of those, for those who don't feel like tearing down an old tv and trying to find tubes that match. It works if you have a bad tube OR a bad transformer which both can be a pain to find, it gets you going but with one lamp bypassed so there's a slightly dimmer section running across the screen but it's not really very noticeable, second video I believe.