Westinghouse SK-32H240S Sob story with a Darfon board

[Tedybear]

First time posting here, hope everyone is gentle.

Picked up this TV used from a gentleman in Phoenix, NY. The guys been fixing electronics (tv/radios/amps) sense Moses was in diapers. He purchased it used with a broken screen. He replaced the screen assy, and it had a fantastic picture.

Fast forward several months. Got a nice burning smell in my office. And one of the CCFL's behind the works started to flip out. Kinda like it was 1/2 lite up. So me being somewhat good with electronics? I pulled it apart and found the good ol' Darfon b070-401 with the center 4301h inverter with a nice burnt up mark on the board.

I replaced it yesterday. Now considering one key detail: This TV has been flawless, even up until that inverter roasted.

So I did the replacement, and of course? It did the turning on for a second--flash back off. It then kicked back on about 3 seconds later to state "no signal"..and then back off.

So we gave it a signal, the wife's wii system. Sure enough, we fumbled around until we bumped into the correct 'input'...audio... We only get a picture for a second before it snaps off.

Now I've been lurking here for a while reading up on this little snot. The only oddball thing I've found? Is when the tubes do kick 'on'? We get a slight electrical hissing sound that comes from under the large heatsink near the multipin connector. (not the power in connector) It could be just a high freq. noise--my hearing is a bit 'odd' and I can pick up on that stuff. It's only active when the CCFL tubes are actually firing up and on. (Big deal--it's about 2 seconds total time LOL)

Any rate. The TV's been given a lot of love with the replacement part. I've removed each inverter and checked for damage as well--anything 'hidden' and there's none. All the resistances are well within range for each other.

I've also done the CCFL test with each indie lamp...each lamp kicks 'on' full as expected.

I must admit to being at a loss. The blue cap's all tested "Open" as well, which is what I expected. Each transformer has almost 100% matching resistance.

Much as I hate to admit being beaten? This is really making me wonder. As for the scorch mark under the chip? It is visable...but not "smoking deep" as in a crater. (more like slightly burnt..not deep. enough to discolor things)

Any help on this one? Considering all 3 transformers appear to be fine? I'm at the loss now.

Thanks in advance for any help! I'm not one to give up without a fight, and my electronics training--while outdated--I still can use a DVM fairly well.

S-

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

No joy yet?


Anyone think throwing a cap kit would do any good? (eBay has them listed for the set, using panasonic replacements) I can't imagine the cap(s) would fail at the exact same time the inverter burnt up.... Just looking for ideas!

S-

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

I'll probably do a cap kit just for giggles and grins. Kinda keeps my soldering skills in check. Even though I just pulled the inverter for the last time...cleaned up all the burn marks. Just to see if I had the arc issue through the burnt parts I did a basic job with a file. Got all the spots off except the deepest burn mark. That one I packed in a bit of high voltage grease--the stuff we use on spark plugs and ignition systems to prevent arcs. Capped it off with a thin strip of electrical tape. Just to see what would happen if we had ZERO chance of any arcing on that part.

Still shut down after a second....kicked on about 5 seconds later to inform us we had 'no signal'. And then kicked the CCFL's off again.

Oh yeah. Board is littered with CapX Capacitors or what ever that problematic brand is. I still do not think that's the issue---as the set was working mint prior to me removing and replacing the bad transformer. Just hard to think if things failing at the exact same time....


So I'll probably do the cap kit just for fun. At this point the set is nothing but an project- Looks like I'll probably keep an eye open for anyone else with a Westinghouse 32" TV with a broken screen. Considering this screen is only a couple of months old?...

S-

[budm]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

https://www.badcaps.net/forum/showthread.php?t=39740
The MOSFETs that drive the transformers are OK? The caps are OK and show low ESR? ETC.

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

As far as I can tell the transformers are firing up normally. My multimeter is basic and does not do in depth testing. I did the test by unplugging each ccfl and then one at a time turning on the set. Each ccfl did light up as expected.

The issue that is driving me a bit crazy, is that the set was working fine, even with the one bulb being out?!? (when it smoked the inverter, I still had a good picture and it did not cut off the circuit.)

Now the capacitors this thing uses? Are sadly the CapXcon type. Due to not having a meter that can do the esr test--I'm left with just visual inspection, and the old school "Put the meter across the terminals and check for an open circuit.". Which all the blue capacitors that 'detect' (or what the tech term would be) for the ccfl's to all have lit up.

I am wondering about the faint 'hiss' sound when it does start the ccfl's before it shuts down. Added to the fact the set actually turns "ON" the ccfl's to tell me that it's got no signal?? And then blinks off?

Shouldn't that be not possible? Or is that another clue as to what might be going on?

I'll see if I can get some photos of the board posted. I have a 5.1 cell phone camera, but it could not get in for the real 'detail' shots. The wifes camera might do better.

(mean while I'll also look into a different meter that supports capacitor testing.)

S-

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Okay. Borrowed the wife's camera and have some assorted photos. Keep in mind I'm not sure what is going on with the replacement inverter. It has some odd coating like an clear coat of some such thing. It really looks like a smeared up mess on the photos.

Also I'm not compressing these photos. Please let me know if they are to big or not quite right.

There is one capacitor that looks flat out no good. That's the one with the green plastic covering next to the heat sink. The top is bulging slightly.

So other then only knowing that all the inverters checked well within their expected resistance. All the little green guys show full "OPEN" or Max resistance? I'm still at a loss.

What does everyone think? Should I just order in the eBay kit

http://www.ebay.com/itm/Westinghouse.../230862176170?

And swap out all of them? I really do not know if that would cure this or not? As I mentioned before, The set worked 100% before roasting the inverter output for only one lamp. I still can't get over that it didn't shut down on the spot. It waited until after I inspected the damage--and then figured out how to use the safety.

Please also keep one thing in mind. While I do work as a tech, it's not board level repair. It's voltage checks, mechanical checks, parts swapping to identify bad boards. We have a service dept that handles all the detail stuff. (In other words, I can do voltage checks, and all checks that my limited meter can do. As far as ESR and component checks? That will get a bit sticky.) I can take direction extremely well, provided a basic multimeter will do. I'll check the one at work to see if it has a capacitor ability---but I think it's a normal hobby type.

S-

(Sorry if I sound a bit gruff. I'm dealing with an severe tooth infection and am not a happy camper)

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Quite interesting.

Reason I find this interesting is that I've found countless posts on the subject. Several people have had the exact SAME issue that I have with this TV. They all seem to get about 1/2 down the path to figuring things out...and then they vanish into the clouds of obscure.

To recap. Just read the prior posts

I have a capacitor kit coming (the one listed on eBay. No one said it was a good kit or a bad kit. So I'm running with it)

I have no clue if the cap's are good or bad. What I am going to do is ask if the meter I'll be bringing home from work will do a good enough job at testing them----or if I'm screwed.

The 'F' rating (sounds great already) starts at 2n and goes to a max of 20uf. I tested it several times. And of course the first cap I pull out of the drawer and blow the dust off? 47uf. So of course the meter pegs to the "Crap can't measure that" mode.

So the question. Will this meter, and this scale do the job enough to test things out.

And I'll even go one step more. When and IF I figure this out? I'll post the reason---also if I just say the he&& with it...I'll post that. In the hopes that the next person isn't left hanging by the nose hairs.

So that's the question. Can this meter do the trick...or am I hosed?

S-

[budm]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

"I've also done the CCFL test with each indie lamp...each lamp kicks 'on' full as expected." What is the indie lamp?
BTW, try heating up the caps with hair dryer for a few minutes and then apply the power to see if the backlights will stay on. You need ESR meter to really find out if the cap has high ESR or not beside the capacitance test.

[SteveNielsen]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

That meter will not be suitable. You'd be better off using an inexpensive tester like this:

http://www.amazon.com/Multi-Test-Tra...pacitor+tester

I think he means he tested the tubes independantly.

[vinceroger69]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

could the other inverter be bad too showing no visble signs of damage can you measure the windings on both see if they match ok

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

That meter will not be suitable. You'd be better off using an inexpensive tester like this:

http://www.amazon.com/Multi-Test-Tra...pacitor+tester

I think he means he tested the tubes independantly.

Yes. I plugged in each tube one at a time and turned the set 'on' Each tube came on normally and then shut down after the 1 second bit.

Windings on the primary and secondary of all 3 inverters are almost a 100% match with each other. 1830 if memory serves on each of the secondary windings. I remember reading about the 3% difference between the resistance being a possible cause--and sense this is a fairly low cost replacement off eBay? I wanted to make sure this would not be the problem.

I removed each inverter, inspected it for heat damage on the underside, and measured the resistance. One of the eBay sellers was nice enough to provide the specs and pinouts.

The only capacitor test I've been able to do. (And from the sounds of it...might be the only one pending a hair dryer and/or different meter) was the generic check for a short test.

Would the esr test be mainly for the electrolytic capacitors? Reason I ask is that I have a cap kit coming from the eBay seller in a few days. Considering 1 cap has a very slight 'bump' on the top of the can--Figure it was good as time as any to change them out. Plus this isn't the first time a cap on that board was changed. One cap had a felt tip marker circle directly under it showing the legs on the solder side of the board.

S-

[SteveNielsen]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Yeah, esr test is for electrolytic, tantalum and solid aluminum caps. It is better to change all the electrolytics at once since any of them could be bad without showing physical signs especially since you've got no way to test them further. There is also a probability that others will go bad soon if they haven't already.

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Well. Looks like I'm in a holding pattern until the cap kit comes in. Odd I never figured I would have to do another one. The video games I work on, some of the older WG monitors, NeoTec,... We used to do cap kits about every 3 years to restore the color back to 100%. Over time they get a bit sloppy. Now our service dept does all that work and we are becoming parts-swappers.

I'll report back once the cap kits come in. The only wild card will be the little blue ones. Ceramic I do believe. I hope they are all within spec. Hate to invest the $$ for the cap kit....and then have to invest in a tool...(and then learn how to use it LOL) And then more caps.

The kit should be here in about 4 working days. Looks like I'm on the small screen until then.


(kinda glad my computers mother board has the solid caps rated at over 50,000 hours.)
(knock on simulated wood.....just in case)

S-

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

I sound like Colombo.

One more question before I call it a day until the caps come in. I did find that the guy I bought the Tv from actually replaced 3 caps. Vision isn't what it used to be, and I spotted two more felt tip marks on the rear of the board, and some cap's that where not CapXon (or CrapExxon....)

I back probed the BL-ON with the red probe and the black grounded. Turn the TV 'on' and it kicks to 4.87vdc. Seems decent...(Then again, the games I work on? We expect 5.15vdc for switched inputs. This is new to me so I'm unsure)

The voltage remains constant while it does the following:

CCFL's kick 'on' for a second..then snap off

Several seconds later the CCFL's kick back 'on' and the screen flashes the warning for no input. Then the CCFL's snap off within a second. Gotta be quick to read that no input warning.

During this time, the BL_ON holds voltage as stated. It's only the 2nd time that the BL_ON goes voltage low as if telling the CCFL's to shut down as it should.

My question:

Sense the command for the CCFL's to remain "ON" is present, and constant until the 'no input' error that is supposed to shut down the CCFL's.

The CCFL's remain lit for only a second before snapping 'off' when first powered up.

My question is: Why are the CCFL's firing up again? Is this normal that the inverter board would refire the CCFL's a second time, only to shut them down a moment later by killing the BL_ON input?

I'm tempted to jumper the BL_ON directly to the 5vdc line. (Tempted, but won't due to the possible issue of making matters worse)

I just find that double flash very interesting..First time on---off a second later. And the set magically turns the CCFL's back on, just a flash so I can see the "no input" warning...and then the CCFL's go black and the BL_ON goes flat as well.

Does that make any sense? Or is my medication playing tricks on me.

S-

[budm]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

The BL_ON should stay HI the second time around until the TV is turn off, when this happen, you should also look and see if the PS_ON also goes low too or not, if not then what you can do is to feed the bl_on line with external 3V via 100 Ohms resistor but you must disconnect the wire going back to the main board otherwise the main board will force the bl_on line low.
Another thing to check also is the DC Voltage right at the 2 legs of the main filter cap (large brown cap with 450VDC rating) to see if it drops down to 170V from >360VDC when the TV is turned on.

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

The BL_ON should stay HI the second time around until the TV is turn off, when this happen, you should also look and see if the PS_ON also goes low too or not, if not then what you can do is to feed the bl_on line with external 3V via 100 Ohms resistor but you must disconnect the wire going back to the main board otherwise the main board will force the bl_on line low.
Another thing to check also is the DC Voltage right at the 2 legs of the main filter cap (large brown cap with 450VDC rating) to see if it drops down to 170V from >360VDC when the TV is turned on.

Interesting. So it is reading 4.7vdc and it should only be 3vdc?


Just trying to figure out how this should behave. The BL_ON is the command line for the back lights. I've read that the ccfl's should kick 'on' and stay 'on'. At least until the logic controller part figures out there is no input. At that time the ccfl's shut down, and the TV still remains 'on' awaiting some input from the remote or the side switches.

Now when the ccfl's are commanded to turn 'off', shouldn't that bump the BL_ON line to low?

The more I think about this the more 'over designed' it seems. I know it makes sense from the designers point of view. But it just seems like part of the setup could have been used in a Rube Goldberg device.

I'll give the test a shot re: the voltages coming out of the supply and the main filter cap when I return from work this afternoon. The more I read about the "CapXon" capacitors and their fail rate--the more I get the idea this could just be a result of 'dirty' electrical signals from the weak parts.

Not sure how the burnt inverter= the current problem. It's starting to look like just a coincidence.

S-

[budm]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Interesting. So it is reading 4.7vdc and it should only be 3vdc? >2.5V is good, typical range is 2.5~5VDC.

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

I'm tempted to carefully remove the BL_ON lead and jumper it with the 5vdc source. Just to see what happens.



It's odd how the set kicks on...and then off? And then manages to kick the ccfl's on the 2nd time? Only to then cut the BL_ON line to shut them off?

Makes me wonder if the board is coming back to life....kicks 'em on...only to have the logic/controller pull the rug out.

Should be fun. I'll be picking up a de-soldering tool from Rat-Shack this afternoon on the way home from work. The cap kit should be here early next week. (I'm good with the de-soldering braid....but it gets old smelling the flux up the nose)

The more I look at the board? The more amazed I am that someone replaced more then just the 3 caps. I've found a mis-matched selection all over the place. And that one with the green sleeve? Is 100% on my to-do list. The top was pressed against the heat sink cover thing with the holes in it.

S-

[Tedybear]

Re: Westinghouse SK-32H240S Sob story with a Darfon board

Well that was a whole lotta nothing.

Cap kit came in, installed. Did fix the one blown cap just under the heat sink cover. (That was bubbled up)

At any rate. I redid the secondary winding resistance. Interesting results sense I brought my meter in from the store.

I didn't do the primary, as with my headache I didn't want to sniff any more solder by removing the inverters a 3rd time.

By the numbers:

1.790 This is the inverter #1 (factory)
1.796

1.774 This is the inverter #2 (replacement)
1.818

1.769 This would be inverter #3 (factory)
1.770

At first the meter I was using ran them all at the same numbers. Once I junked the auto ranging POS the numbers are a bit off...But I have to wonder if they are off enough to create that shutting down?

Low is 1.770 and the High is 1.818

With the net difference being: 0.048 total span

This is the only thing that I can think of. I'm outta ideas at this point (and doing this with a series of migraine headaches is also giving me more then a headache.)

Any ideas would be welcome.

S-

[Tedybear]

Re: Westinghouse SK-32H240S Anything else we can chase after?

Bumping up.

I've also put a listing on our local c-list to see if anyone has one of these set's with a broken screen for sale cheap. Might be simpler to swap the screen out then play around with this.

S-