Re: Sharp LC-50P66U Power Cycling
Got the set working. Another eBay seller advised me to check the backlights. They were not defective, but it occurred to me that this symptom was very similar to a backlight fault. It didn't make sense though, because it didn't look like there was any way for the mainboard to sense a backlight fault and shut down. However, I started comparing the two power supplies and discovered that some components (mostly resistors) had different values. I also noticed that although the part numbers on the boards matched, the sub-numbers on little stickers were...
packrat79
Member
Last Activity: 04-21-2024, 07:39 PM
Joined: 03-15-2017
Location: New Brunswick
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Re: Sharp LC-50P66U Power Cycling
The BL-ON signal cycles on both sides of the connector. As unlikely as it seems, everything points to the mainboard. I guess I'll have to order another one and see what happens.Leave a comment:
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Defective Replacement LED Strips?
A few weeks ago I picked up an LG 55LN5700, the backlight would stay on just long enough to display the LG logo and then shut off. It seemed like a pretty obvious backlight failure, and I've serviced a number of similar LG sets with good results, so I went ahead and ordered a new set of backlight strips (from China of course, and had to wait almost a month). I installed them all and ran the set for several hours, and all seemed good. I sold the set to a customer and a few days later he told me the picture was randomly shutting off. So he brought it back and it started doing the same thing for... -
Re: Sharp LC-50P66U Power Cycling
Yes that is exactly what I did:
Pin ID / V in standby / V powered
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12VDC 12 12 steady
Vcc 16 16 steady
P-ON 0 ~3.1 steady
BL-ON 0 2.2 cycling
DIM 0 2.2 cycling
That's basically all there is on that connector, plus ground connections of course. The BL inverter (part of the power supply) does not send any feedback signal to the mainboard for detecting faults, something I have seen...Leave a comment:
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Sharp LC-50P66U Power Cycling
This set was brought into my shop a few weeks ago, the power supply was totally dead. Customer said the set had hardly ever been used. I ordered a power supply from an eBay seller, after installing the set would power up just long enough to display the Sharp logo, then shut off, and keep repeating. The voltages to the mainboard (12 and 16VDC) remained steady, as did the P-ON signal to the power supply, but the BL-ON and DIM signals cycle along with the power. I was sure the mainboard must be faulty too (lightning strike maybe?, so I ordered one, installed it, and got the exact same result. The... -
Re: Samsung PN58A550S1F No sound / Green squares
OK gave it a try, posted a picture of the result. Those two bars are still present, but everything else is a solid color which cycles from white to red to green.... then the TV power cycles off and on (something I forgot to mention in my original post) and it starts over again. I suspect blue would be the next color in the sequence.
The power cycling suggests the mainboard (this is a known fault), but the fact that the two bars are still present worries me that the logic board may also be faulty. Any ideas?...Leave a comment:
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Re: Samsung PN58A550S1F No sound / Green squares
Oops, that is the mainboard, my mistake. Here is the logic board:
[URL="https://www.ebay.com/p/Samsung-Pn58a550s1f-Main-Logic-Control-Board-Lj92-01457a-Lj41-04802a/1219768041"]https://www.ebay.com/p/Samsung-Pn58a550s1f-Main-Logic-Control-Board-Lj92-01457a-Lj41-04802a/1219768041[/URL]Re: Samsung PN58A550S1F No sound / Green squares
Oops, that is the mainboard, my mistake. Here is the logic board:
[URL="https://www.ebay.com/p/Samsung-Pn58a550s1f-Main-Logic-Control-Board-LjLeave a comment:
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Re: Samsung PN58A550S1F No sound / Green squares
Didn't have time to take any more pictures, but it is identical to the one shown here:
[URL="http://www.coppelltvrepair.com/p/1033/repair-service-for-samsung-pn58a550s1f-pn58a550s1fxza-main-board-bn97-02039a-bn94-01660a-causing-tv-power-cycling-failure-to-power-on-or-loud-screeching"]http://www.coppelltvrepair.com/p/1033/repair-service-for-samsung-pn58a550s1f-pn58a550s1fxza-main-board-bn97-02039a-bn94-01660a-causing-tv-power-cycling-failure-to-power-on-or-loud-screeching[/URL]Re: Samsung PN58A550S1F No soundLeave a comment:
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Re: Samsung PN58A550S1F No sound / Green squares
I'll try and get more photos if I have time. Looking around, I see there is a common fault with this mainboard which can cause similar symptoms (power light blinking indefinitely, no video), so I'm really leaning that way now. Tried disconnecting the LVDS cable from the main to logic board, and the LED's on the logic board continued blinking as before. Maybe an indication that they aren't getting any signal.Leave a comment:
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Re: Samsung PN58A550S1F No sound / Green squares
How do I run the test patterns? I don't see any info on this in the service manual.
Something that concerns me is the fact that I can't turn the power off / on with the buttons... do you think this could be a mainboard issue, or is the mainboard trying to communicate with the logic board and getting stuck?Leave a comment:
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Samsung PN58A550S1F No sound / Green squares
Got this set in my repair shop, looks like a logic board failure but I thought I'd get a second opinion before ordering a replacement. Set powers but power light remains blinking, has two squares on the screen (see photo) but no sound. Buttons produce a beep when pressed but don't do anything. Logic board has two diagnostic LED's that blink rapidly. All voltages from the PS measure correctly.
Any opinions?... -
Samsung UN50EH5000 Double Image
A customer brought this set in yesterday, the problem is that most of the picture (except for the top several inches) is jittering up and down, making it look like a double image. I've attached a photo. I'm wondering if this is a panel issue, and for this reason: I also have a Vizio E55-C1 with a very similar problem, and just tried replacing the T-con board but it made no difference. That leaves only the mainboard or the panel, and I don't want to gamble time and money on mainboards if there's a good chance the panels are bad.
Has anyone seen this problem before and might be able to give... -
Re: LG 47LN5750 Service Menu
Yeah I now realize the service menu is pretty hard to access. Turns out I don't really need it though, as the backlight brightness can be adjusted via the consumer picture menu. I dialed it back from 70 to 50, and will advise the customer to keep it as low as they can tolerate to prolong the life of the set.Leave a comment:
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LG 47LN5750 Service Menu
Just serviced one of these in my shop, replacing a bad LED backlight. To prevent repeat failures, I usually just update the firmware, but I discovered that the firmware was already up to date when the LED failed. So my next idea is to reduce the LED brightness via the service menu, as I did recently with an RCA. Does anyone know how to access the service menu on these LG smart TV's, with the "magic" remote?
IMO, the LED backlights on modern sets run way too bright, more than the customer will ever need unless maybe the TV is outside in full sunlight. I think they're set that... -
Re: New Members - please post your introductions here
Just making my first post here as per the rules, glad to find an active forum for electronic tech discussion. Used to post to sci.electronics.repair many years ago but usenet groups seem to be a thing of the past now.Leave a comment:
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