RCA 37 WD12YX1 Flickering Backlights

[Mike Jenk]

HELLO FRIENDS,
Here is what I got, while turning this set on the Video and Audio work great , but the back lights flicker on and off like it has a bad bulb in it. Some times there is no flicker at all when the set is turned on and while it is on it stays lite up until turned back off and on. Now there is no set time or reason this happens and there is no dark spot across screen when on as if a bulb was bad.
I found some bulged caps in the PSU and replaced them, Ohm ed out both transformers on the inverters and they have the same readings when compared pin for pin. Have 24 volts , 5 , 3.8 on inverter boards from CN01and CN201, also this was measure while flickering and normal display. I don't know how BL ON is controlled , I see the pin lay out on board but don't know what they stand for, there was a similar post here in JUNE with a schematic , but is different then mine.
Thanks in advance.
Mike

[selldoor]

Re: RCA 37 WD12YX1 Flickering Backlights

There are no hits on google for WD12YX1 is that correct.
Start by unplugging, cleaning and reseating all cables to do with lighting and the panel.
You will need to check the wiring right up to the bulbs and the bulbs themselves.
Try re soldering the inverter transformer if that is what it is..

[Mike Jenk]

Re: RCA 37 WD12YX1 Flickering Backlights

There are no hits on google for WD12YX1 is that correct.

Its actual Model # 37WD12.

So funny thing, while the set was laying flat screen side down, it would stop back light flickering after about 3-5 minuets of being on and stay lite. So still thinking like its cold related and takes a minute to warm up I used a hairdryer and started around the Master inverter and it stopped flickering instantly. I have narrowed it down to around the surface Mount caps just above the transformer.

[tom66]

Re: RCA 37 WD12YX1 Flickering Backlights

Looks like you are pretty close... Is there any way to focus more heat on different parts... in particular I would be considering those 8 MOSFETs as well. An intermittent short on one part could cause the problem.

[Mike Jenk]

Re: RCA 37 WD12YX1 Flickering Backlights

Looks like you are pretty close... Is there any way to focus more heat on different parts... in particular I would be considering those 8 MOSFETs as well. An intermittent short on one part could cause the problem.

Thats the next thing, I am going to put a piece of paper on the end of the hair dryer to create a small tipped funnel area(my heat gun has no tips), then start from one edge to the next, its hard due to it instantly works and after its starts up it comes on almost instantly. Has tried to blast it cool air with TV off and on , but starts back up after about 30 seconds.

Will keep you posted.

[tom66]

Re: RCA 37 WD12YX1 Flickering Backlights

Maybe once it's running freeze spray parts till it falls over?
I have had good luck with freeze spray identifying intermittent faults.

[Mike Jenk]

Re: RCA 37 WD12YX1 Flickering Backlights

I will get back to this have been a little busy. no luck with freeze spray, add heat and instant on. Is it possible to just use budm's way of testing the inverter with just 1 back light bulb hooked between master and slave inverter on this set.

[tom66]

Re: RCA 37 WD12YX1 Flickering Backlights

It will usually shut down when you try to do that unless you disable the protection scheme.

[selldoor]

Re: RCA 37 WD12YX1 Flickering Backlights

Still think you should work on the 8 mosfets- Do the test in here
https://www.badcaps.net/forum/showthread.php?t=10419
when its unplugged. The datasheet is here http://www.digikey.com/product-detai...0ACT-ND/965623.

Also if they are accessible when its switched on but off ??! press each contact lightly with a non conductive stick - wood/ plastic toothpick.