Lights go out on Westinghouse LCM-19v7

[kingofcoins]

Back at it...This is a like-new 19" LCD Westinghouse LCM-19v7...replaced all 8 of the Capxon caps on the DAC-19M001 P/I board with Panasonic FM's even though they all tested good with low ESR's. Was giving about 10 seconds to powerout and as attached pic shows the left half of screen was vertically srtiped. After repair it all works for maybe 5-10 mins then the backlights start blinking...AND soon its lights out, though green power led stays lit. Turning unit off and right back on restores display but if warm its off in a few secs. If you wait for awhile before cycling power then it stays on longer. Does not seem to come back on itself unless shut down, cooled and rebooted.
So what do you think...where should I test first guys ?

***>BTW Plain Bill is very right about Digi-Key, caps, and shipping. I have done about 10 monitors and just ordered a new batch of 66 Panasonic and Nichicon Caps, and the postage was all of $2.92...heck I even got box in less than 2 days !

[alexanna]

Is the problem with the left side of screen fixed?
I would start on the mins. to black problem with substuting known good ccfl[s]
Al.

[romansroad]

If you're seeing the same pic you posted, perhaps reseating the cable to the panel would be helpful. It sounds like there may be 2 issues here; the half screen and the backlights. Consider checking known good ccfls and the windings on the HV transformers.

[kingofcoins]

The vertical lines however got fixed, BUT the problem is now:

"After repair it all works for maybe 5-10 mins then the backlights start blinking...AND soon its lights out, though green power led stays lit. Turning unit off and right back on restores display but if warm its off in a few secs. If you wait for awhile before cycling power then it stays on longer. Does not seem to come back on itself unless shut down, cooled and rebooted."

[romansroad]

I see, then I agree with Al and see if you can sub in known good ccfls. If not, then check the primary and secondary resistance of the HV transformers looking for opens or shorts. Keep in mind the resistance can be quite low so be sure your meter can handle that precision. Finally, if the unit is worth it to you, you can always order new ccfls. Many here have used ccflwarehouse and they have been cheap and fast, but there are no doubt other suppliers.

[kingofcoins]

This is getting really strange now....after futzing with the cables, the lcd's auto settings, and cycling the unit off, on, and reboot, this 19v7 settled in and I have now run it for 3 different periods a total of 5 hours with no issues at all !
I've tried tapping the unit, wiggling cables, and resetting its menu but cannot get it to show any sign of failure.
Did I wake up some component that has been inactive for some years ?
The work I did was to replace all the caps...and even though I initially saw those veritcal lines on the left side, and saw the backlights blink, and watched the unit go black...all after the repair ...all have vanished and its working like new again.
......What do you think happened here ?

[romansroad]

Just like my Samsung on another thread.....the electronics are learning to fear the full weight of the BadCaps forum !

[romansroad]

Seriously, perhaps you improved a connection on the ccfls....it may be temporary....let it cool overnight (or put it outside for 20 seconds!) and try again. You know from all your prior fixes the expansion coefficient of metals and the contraction of them when cold.

[kingofcoins]

OK Now 24 hours cold and unit wouldn't display at all...it turns green light on then a split second back light flash accompanied by a phzzzzit and led goes amber, does same on cycling or waiting. Does this still sound like lamp connection breakdown, or is it some failing component in the inverter section ?

[retiredcaps]

Originally Posted by kingofcoins

Does this still sound like lamp connection breakdown, or is it some failing component in the inverter section ?

Start with post #13 and see

http://www.badcaps.net/forum/showthread.php?t=10419

Also, check the backside for possibly poor/suspect solder joints (also described in above document).

[kingofcoins]

I did fix a couple solder spots with small holes, but overall quality is very good.
I gather my micro-second flash is not the '2 seconds to black', but perhaps a shorting transistor or mosfet ?
Does that make more sense as the history after cap repair was it didn't work, then it did for about 4 hours, they after a day off it barely blinks and goes to amber?



[QUOTE=retiredcaps;141282]Start with post #13 and see

[url]http://www.badcaps.net/forum/showthread.php?t041

[retiredcaps]

Originally Posted by kingofcoins

I gather my micro-second flash is not the '2 seconds to black', but perhaps a shorting transistor or mosfet ?

Does that make more sense as the history after cap repair was it didn't work, then it did for about 4 hours, they after a day off it barely blinks and goes to amber?

Hmm, a micro second flash would be more of a shorted transistor or mosfet.

We will need pictures of your boards.

[fuhrer]

hi to all ze members..im new here at badcaps.. umm we do things like this: we short ze ref or timing pin of the inverter i.c.this will force ze inverter to work even if there is a problem with the lamps or the transformers.

[fuhrer]

just a quick way to check if the problem is witin ze inverter ..hope it helps..

[PlainBill]

[QUOTE=kingofcoins;141330]I did fix a couple solder spots with small holes, but overall quality is very good.
I gather my micro-second flash is not the '2 seconds to black', but perhaps a shorting transistor or mosfet ?
Does that make more sense as the history after cap repair was it didn't work, then it did for about 4 hours, they after a day off it barely blinks and goes to amber?

Originally Posted by retiredcaps

Start with post #13 and see

[url]http://www.badcaps.net/forum/showthread.php?t041

Whoa!!! There are two possible failure modes being described here.

'Two seconds to black' is a fault where the inverter controller shuts down due to an error such as too high an output voltage, too high a current through the CCFLs, etc. The description is somewhat misleading because the delay can be less than a second, and can be more than two seconds. In virtually every case, the power LED will stay 'active' - green or blue as long as a valid video signal is present.

You seem to be describing another problem - the power LED going to amber even though a video signal is present. That is a totally different problem. For that look to the logic card.

PlainBill

[kingofcoins]

Let me know when we need bottoms too...

[retiredcaps]

Originally Posted by PlainBill

Whoa!!! There are two possible failure modes being described here.

My lack of comprehensive is positively correlated to the amount of holiday cheer over the last 48 hours!

[retiredcaps]

Originally Posted by kingofcoins

Let me know when we need bottoms too...

There are a number of voltage regulators on the logic board that you can test. List the part numbers and report the voltage on all pins for all them. U13, U6, U12, U8, and U10.

Not related at all, but on the power board, there are two green picofuses. Check to see if they are open or not.

[kingofcoins]

The pico fuses F200, and F201 both measure about 0.5 +/- ohms.

BTW the readings out of the power to the logic are 3.2v, 5.0v, 20.0vdc

The logic REGULATOR datas...
U6....3.3V, 0.0V, 5.0 VDC part # BA33P 133CB
U8....0.0, 3.2, 5.0 VDC part # AMC 1117 33F0540FJ
U10...0.0, 2.0, 5.0 VDC part # AIC 1084-18PM 783CA
UI2....0.0, 0.0, 0.0 VDC EH11A 539BE
UI3....0.0, 0.0, 0.0 VDC EH11A 539BE

The middle leg of U10 is cut off.
The unit was lighting up for almost 2 seconds with that pzssit while I was running these checks, then back to amber.

[retiredcaps]

Originally Posted by kingofcoins

The logic REGULATOR datas...
U6....3.3V, 0.0V, 5.0 VDC part # BA33P 133CB
U8....0.0, 3.2, 5.0 VDC part # AMC 1117 33F0540FJ
U10...0.0, 2.0, 5.0 VDC part # AIC 1084-18PM 783CA
UI2....0.0, 0.0, 0.0 VDC EH11A 539BE
UI3....0.0, 0.0, 0.0 VDC EH11A 539BE

According to PlainBill, low dropout (LDO) voltage regulators have a +/- 1% spec.

So U10 is out of spec. It should be 1.8V DC.

U12 and U13 should have voltages on it. In addition, I can't tell from the part number what the LDO output voltage should be.

For U12 and U13 test to see if these are shorted.