Samsung LN40B550 turning off after 5 min.

[budm]

Re: Samsung LN40B550 turning off after 5 min.

Sure, the voltage on the large caps is 392V when on

So at least you do have PS-ON signal and the PFC is working.
So after 5 minutes, do you still get the 392VDC? If not, then need to find out if it is due to PS-ON drops out or the PFC drops out.

[jason123]

Re: Samsung LN40B550 turning off after 5 min.

Just an update... turns out one of the inverter transformers had a primary short.. I replaced it and I'm back in business.. thanks for the help.

[budm]

Re: Samsung LN40B550 turning off after 5 min.

Thanks for the follow-up.

[bold_fusion]

Re: Samsung LN40B550 turning off after 5 min.

What is your board number, bn44-xxxxxx?

Hi @budm,

Quite simply, I can see that you are the savior of this forum... thanks! Okay for an additional question?

Like the OP of this thread, I have a Samsung Inverter Board BN44-00264B that happens to sit in my Old Samsung LN40B540 TV (trying to squeeze a few extra years out of it before the junk heap).

As I discussed in another recent post (sorry newb here, can't make new post AFAIK), the display is blinking-off for a few seconds at a time, while the audio is still functional. When I dial the Back-Light setting down to 0/10, the blinking off goes away; however, every so often the Back-Light setting will reset to 10/10 (!), and then the blinking off comes back until I re-apply the Back-List setting of 0/10 :-\.

Since I don't see any bulging caps or burn marks near any of the inverter transformers (checked the top of the 4 transformers, but didn't remove them to visually inspect the bottoms), I'm leaning towards one or more of the back-light CCFL lamps being burnt to a short, and thus a protection circuit is disabling the display for a few seconds at a time (?), as shown in this video:

https://www.youtube.com/watch?v=Dh01ZepjDp0

Also in the above video (which doesn't use the exact BN44-00264B but something similar), they appear to have a good way to simply bypass/disable the lamp which is drawing too much current; since I'm okay if one or a few of the lamps are turned off in the short-term, I'd like to try this fix.

However, I can't align the test points that the video author uses with his different board with the corresponding components/pads on my BN44-00264B.

Moreover, I'm so darn close to finding the schematic/circuit-diagram for it, but can't quite find it. I've found schematics online for BN44-00264A, BN44-00264C, and I was hoping they would be very similar, but the component label numbers are different :-\. Finally tonight, I found the Service Manual for the Samsung TVs containing BN44-00264B, but as the poster mentioned above, that discusses overall TV system diagnostics, but not specific component-level testing repair of the Inverter Board, BN44-00264B :-\.

I've attached a photo showing how I've read the Model Number BN44-00264B.

Is there any chance you might be able to find the BN44-00264B schematic/circuit diagram?

Any assistance *enormously* appreciated!