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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
philips 50pfl3707/f7 no power after storm

 

 


sunsumsavsamsky
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Sep 14, 2017, 3:37 AM

Post #1 of 5 (382 views)
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philips 50pfl3707/f7 no power after storm Can't Post

So it took a surge from a lightning storm and now just blinks a white led 5 or 6 times and then clicks off when I try to power it on. Power supply is a ba21t0f0201 2 ...

http://assets.shopjimmy.com/media/ca...-001-top_2.jpg

Fuse is good and no bulging caps. Nothing looks scorched. Quick continuity testing produced no shorts or anything obvious. The pins to the main board aren't labeled but there are labeled diag rails that you can put your leads on (3 p-on 12v - j747, j746, j757 / 2 p-on 5v - j758, j759 / 1 all 3.3v - j755 / 2 hot 17v - j706, j799) and they produce the correct voltage when powered on, although the 5 volt rails are showing 4.92'ish (problem?). I pulled the caps in that area. They were low but still within 5% tolerance. It just occurred to me that I didn't measure the relay voltage. I guess I'll go there next. There were also a pair of diodes down in the .3 range that I thought I'd change out. There was one at .2 but after researching it a bit I discovered it was a schottsky diode and that it wasn't an unusual reading. I guess I'll go ahead and test all the resistors for the correct ohms.

What's baking my noodle now is I went ahead and went for the "easy button" and ordered another power board off ebay. As soon as I plugged it in, the screen came on without hitting the power button. I thought ... great .... that was easy ............ until I turned it off. It wouldn't turn back on and no response at all from the power button. If I unplug it and plug it back in, it does the same thing as the first power supply - it clicks on ..... then clicks back off after a few seconds ....... with one exception ......... no blinking white led. If I disconnect it and let it sit for about a 1/2 hour, then I get the screen back ........ until I turn it off.



jts1957
Veteran


Sep 14, 2017, 10:27 PM

Post #2 of 5 (362 views)
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Re: [sunsumsavsamsky] philips 50pfl3707/f7 no power after storm [In reply to] Can't Post

The picture link here doesn't work. The one at Badcaps Does work, but shows board for a 50PFL3807/F7. Also, the ba # doesn't match one in body of your post.

Which model # / board is correct?


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Location: Far, Far Away


sunsumsavsamsky
New User

Sep 15, 2017, 1:13 PM

Post #3 of 5 (353 views)
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Re: [jts1957] philips 50pfl3707/f7 no power after storm [In reply to] Can't Post

wooops .... I put in the truncated link ...

http://assets.shopjimmy.com/media/catalog/product/cache/1/image/f8f28dc4a19c21aeb55ee5774693fb5d/s/h/shopjimmy-a27uampw-001-top_2.jpg

yep .... different model tv but same power board ba21t0f0102 2

A few more tinkering tidbits .....

On the original storm fried board, the schottky diode at d703 (I'm assuming it's schottky from it's markings (sb3a0 bl) - http://www.datasheetspdf.com/datasheet/search.php?sWord=SB3A0 even though the board symbol on the backside shows a regular diode) - anyway ..... it's exhibiting the symptoms of a bad schottky ..... according to this anyway ..... http://www.electronicrepairguide.com/schottky-diode.html. When I set the meter for ohms, there is no neglibigle difference when switching the probes between anode and cathode. When I do the same thing on the schottky of the board I bought and that powers up the tv ..... sometimes ...... it does show the requisite drop between anode and cathode. I will try the schottky from the ebay board on the storm fried board next.

I'm beginning to wonder if the main board got cooked too. Or at least the ic's. I watched a youtube video of someone who had an LG with similar symptoms as my ebay board. Only powered up sporadically. Everything tested ok on the power board so he cooked 2 of the ic's under a 50 watt halogen lamp for an hour to sort of reflow the solder balls under those chips. Then the tv started powering on consistently ...... or at least for the duration of his video anyway :)

The kicker that makes me wonder if I've got a similar situation as the LG guy is that with the ebay board, I noticed that when I turn it off, voltages on all the rails, 12 and 5 are still present .... ie ...... the board is still powered on even though the rest of the tv is off. They don't revert back to their standby voltages. The LG guy on youtube had the exact same thing happening to him.


(This post was edited by sunsumsavsamsky on Sep 15, 2017, 2:12 PM)


sunsumsavsamsky
New User

Sep 15, 2017, 2:58 PM

Post #4 of 5 (346 views)
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Re: [sunsumsavsamsky] philips 50pfl3707/f7 no power after storm [In reply to] Can't Post

oh man ........... I guess the devil is in the details. So the board inside the tv was a ba21f0102 2 so that's what I looked up on ebay. I did notice that the tv model was different 50pfl3807 instead of 50pfl3707 but I figured they both used the same ps. It was a craigslist buy and the original owner claims to have never opened the set. From what I gleaned on shopjimmy ...... it looks like I need a ba21f0102 4 or 1. So ya .... about all those long winded details in the previous posts ......... NM :)


sunsumsavsamsky
New User

Sep 16, 2017, 2:57 PM

Post #5 of 5 (329 views)
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Re: [sunsumsavsamsky] philips 50pfl3707/f7 no power after storm [In reply to] Can't Post

Ok ..... now I'm buried in part number semantics ........

According to shopjimmy, I can use this board ....

http://www.shopjimmy.com/philips-a21uampw-002-power-supply-unit.htm

... which is a ba21t0f01 4. The serial number on my unit begins with DS1 and according to that link, this should be my board.

However, that a21... number does not match mine. Mine says a21uauh

 
 
 


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