Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work).

[Xandros]

Hi there! Great forum this. Hopefully someone can help me out. Basically my tv's been in storage for about 6 months (and by storage I mean someone's cold garage). Finally got it out and in my new place yesterday fully expecting it not to work, plugged it in, fired it up. It started working straight away to my surprise, didn't see any problems until few seconds later the screen began to flicker, got progressively worse and erratic over a few minutes then just went black. Power cycling it seemed to get the screen to come back on but it would again immediately begin to flicker and go off but it took less and less time to do that until eventually now it turns on but the backlight doesn't come on at all.

I shone a torch through it and discovered the screen is still working, and I managed to get sound through the speakers too so, seems like it is just the backlight not working. I found this post on these forums where SuperSkippy seems to have had the same issue as me with the same tv, except his was a blown fuse. I have tested the two fuses I could find on the power/inverter board and they aren't blown.

I was about to start testing the capacitors with my multimeter but, I've never tested caps before, the multimeter does have a capacitance setting but I don't think it's ranges are sufficient. It's automatic ranging with the capacitance test and when I tested the large yellow cap as suggested in the linked thread which says on it that it's 450v and 100uF, my multimeter eventually came up with a 204.8uF reading. Am I dong something wrong (must be, unless my meter is just pants, it was only a cheap thing)?

[sordids999]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

posting pictures of the back of your tv showing the parts may help you more

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Sure, here's the back of the tv, and minor close ups of both the boards. Camera isn't fantastic though so don't expect a marvel of photographic intensity though I can do a even closer close up if needs must of course. Also for what it's worth, here's the wiring diagram for the power board (the one linked in that thread doesn't work but I found it elsewhere).

[sordids999]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

So have u tested for voltages of the psu ?

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I didn't get to unfortunately, shortly after I posted the pictures I went back to start some real testing of capacitors, voltages etc my el cheapo multimeter decided to stop working.

Think I might just get a replacement board. There's one on eBay for the same cost of a new multimeter.

[Andrew F. Ali]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Your board should be BN44-0034a. I see you posted a diagram for BN44-0034b. Not too sure what the difference might be. However, you need to check if 24Vdc supply on the Power Bd is produced. If you have 24Vdc, check if BLU-ON signal is coming from the Main Bd. If it is not generated from the Main Bd, then you have a Main Bd problem. If BLU-ON signal is generated then you could have an Inverter problem. Inverter IC, HV Transformer or an open fuse on the Inverter section.

[sordids999]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

The Psu board is BN44-00340B and andrew is right best check voltages incase its the mainboard,inverter etc

[budm]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Disconnect the cable between the main board and the power supply board then power the unit and see if the backlights will come on, no need to hit the power switch.
BTW, the board has pull-up resistors for the PS_ON and the BL_ON.

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Hi, thanks for the replies. Tried the suggested checks. Powered tv up with mainboard disconnected, but couldn't see any backlights. Tested for 12v on pin 1 of the plug going to the transformers, reading 12.8v, and tested BLU-ON pin4 on the mainboard output and it was showing over 4volts.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

seems to be pointing towards inverter.

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Is there a particular way to test the inverter with a multimeter to determine if it's the culprit? I'm unsure on what values I should be looking for when testing pins etc. or in fact what sort of test I should be running and where. I've uploaded a picture of the inverter at any rate.

[Andrew F. Ali]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Yes by measuring voltages you can use a multimeter to determine if the Inverter is defective. Most of these Samsungs require 24Vdc to power the Inverter circuit. Are you getting 24Vdc on any of the other pins? With the black lead on your multimeter connected to the bare metal back and the Red lead carefully held turn on the TV and measure.

[budm]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

The inverter circuits of this board does not run off the 24V power supply, it runs off the PFC Voltage booster which is >360VDC, the main inverter is on the power supply board, the board connected to the lamp is the balancer board.
You need to find out if you do have >360VDC on the fuse (tested good per your post) in the middle of the board, use the negative leg of the main filter cap as the ground ref. point.

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Just to be sure, the large yellow caps in the middle next to the fuse are the main filter caps right? I tested it as suggested, my meter comes up with OL when I touch either side of the fuse when using those caps' negative pins.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

do you think it could be the balancer board budm?

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

I was thinking from the get go it was the power board personally, especially when I learned the main inverter is on it. I've tested some but not all of the caps on it, some I don't think I can test with this multimeter because it only goes as high as 400uF range according to the manual. The two big yellow caps both say on them 100uF but they read over 200uF, two of the small caps in this same area of the yellow caps are also causing the meter to read OL even though they are fairly low uF ratings (one is 1uF according to side of the cap, the other is 47uF.

There's only three other caps on the board that check out, all the others seem to be too higher uF rating for my meter I guess. They all come up with OL eventually if I do test them.

I've also tried testing the various MOSFETs but I'm getting odd readings from most of them. One definitely seems to be a dud at least but it's either that or the fact I'm testing it in-circuit that's causing the unexpected readings making it look broken down.

I'm going to order a replacement power board and keep my various appendages crossed in the hope the problem is fixed, unless anyone can offer any other suggestions I might try to isolate the issue further?

One thing I do want to ask about the power board and if I order a replacement, getting the board seems easy enough but I notice the revision level on this board is 1.4 dated 17th June 2010. Should I make sure to get a like for like board, same revision as well? Or does it not matter so much provided it's the same model?

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Well this is annoying. I finally got the replacement power board through this morning, looks all good but upon inserting it and powering it up, the tv won't switch on at all. No red standby light or anything, no response to the buttons or the remote. When I put the old board back in the red standby light does come on (except obviously same symptoms as before with the backlights not firing up).

I guess I got sold a dud board? I was considering emailing these guys and getting them to replace it but I've been looking at there returns policy, seems like I might have issues there. They claim all the boards are tested and working before they ship but clearly that's a lie, unless it got broken in transit - which I wouldn't put it past it seeing as the packaging they shipped it in was wholly inadequate for the job.

Edit: I think I'll make a new topic for this issue, to avoid confusing things.
Edit edit: On second thoughts I think I may have discovered the problem. There's a crack in the board around the power inlet. In fact it's clearly bent slightly. They bloody well have that back.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

Well this is annoying. I finally got the replacement power board through this morning, looks all good but upon inserting it and powering it up, the tv won't switch on at all. No red standby light or anything, no response to the buttons or the remote. When I put the old board back in the red standby light does come on (except obviously same symptoms as before with the backlights not firing up).

I guess I got sold a dud board? I was considering emailing these guys and getting them to replace it but I've been looking at there returns policy, seems like I might have issues there. They claim all the boards are tested and working before they ship but clearly that's a lie, unless it got broken in transit - which I wouldn't put it past it seeing as the packaging they shipped it in was wholly inadequate for the job.

Edit: I think I'll make a new topic for this issue, to avoid confusing things.
Edit edit: On second thoughts I think I may have discovered the problem. There's a crack in the board around the power inlet. In fact it's clearly bent slightly. They bloody well have that back.

for sure, return to sender, broken board.

[nomoresonys]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

who is that sending out broken boards, so we can avoid the same situation?

[Xandros]

Re: Samsung LE40C530; turned on, flickered, now no backlight (but picture/sound work)

bixreclamation.co.uk - found them googling for the part, also the cheapest I could get it at £20 delivered. To be fair it may not have been their fault (well, not entirely), the packaging does appear to have had something large either sat on top of it or dropped on it at some point, possibly the cause of the board's damage, so UPS are likely to blame. However as stated Bix haven't exactly packaged it very well; they stuck the board in a layer of bubble wrap and then put that into a thin not-fit-for-purpose box which itself was wrapped in black tape. Any kind of mishandling would have resulted in damage I reckon.

I've emailed their returns address anyway so shall see what they have to say. I suspect though they may not be forth coming with a response. Just comes across like they're "that sort of company". Maybe I'm wrong...