My terminology may be wrong...as I said I am back into software and happen to be implementing watchdogs currently...sorry.
But in the electronics field I call "watchdogs" the circuits responsible for monitoring various failure conditions (OVP, UVP, lack of secondary), which all could cause the PFC to shut down. They may not be "active" watchdogs as in the software world and again my terminology in that regard may be incorrect and misleading, for which I apologize.
My logic was to exclude (hack) all possible sources of the PFC shutting down thus eventually...
CoppellTVRepair
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Not necessarily, the best proof of which is that the PFC *is* working when the track is cut.
I may get back to the drawing board once I do the other tasks...which kind of never ends, especially now that I am back at writing software (which is a lot of fun I've recently lost reverse engineering electric circuits), but in the meantime I believe I've cut either the final or at least one of the feedback signals that shut down the PFC...like OVP and UVP.
So it might not be the PFC itself that is bad, it may be the watchdogs or it may be simply (and that's what I think) that...Leave a comment:
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I thought it would be kind of pollution to just upload pictures that are already there...should have included the link to the post I was referring to, sorry...it has all the pictures already and what's missing I can upload:
https://www.badcaps.net/forum/troubl...ot-operational
I can also draw up the schematic from the board...I know I did at some point and found at least one instance of a bad high voltage divider resistor...which is why I suspect...Leave a comment:
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No offense meant and definitely not trying to start a war here or even a pissing contest, but Nick used to send us boards he couldn't repair and follow our videos for clues...not sure if he still does, it's irrelevant.
However it may sound I am keen on believing I sill have the technical edge on him.
He's a good kid, nothing against him whatsoever, it's just I really and honestly do not think I can learn how to repair power circuits from him. Still repairing an occasional XVTx73SV main board with NTR stamp on it :-)
But this one has me stumped and I am of...Leave a comment:
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Ah, forgot to say...the cut track, while keeping the board up and keeping the PFC does not appear to be a solution to the problem.
I do not have the whole TV, unfortunately, I do most power board repairs merely bench testing.
I believe I've tried that hack with a customer once before and they reported it didn't fix the TV; could be the hack is not sufficient, could be the TV had other problems too.Leave a comment:
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Sharp Aquos 80" TV ~ Model # LC-80LE844U ~ Not operational, Take 2
There's a thread on the site titled "Sharp Aquos 80" TV ~ Model # LC-80LE844U ~ Not operational", detailing the process of the most common problem affecting power supply board PSD-0888D.
For the sake of bringing something of value I'd also add (even though it probably belongs in the thread itself) that what's described there is one of the TWO possible variants of the failure - blown IC, blown fusable resistor 2.2 Ohm or 2 Ohm.
The other is an internally failed, but not shorted IC, resulting in resistor that's still intact, but the board spontaneously losing power... -
Thank you very much...I needed to hear that from experienced pro.
I'll sleep over it (some of it I can actually remember from my voltage multipliers course in college) and will get to test when other work clears up, then report here. I firmly believe one has to give if they take.
Very rarely seen bad film capacitors in TV power board BTW. Can't say never, but definitely rarely.
Fluke 87v and Tektronix scope are my measuring devices and I'd put my life on them if I have to....I am not rich enough to use cheap tools.
20 years into it I still say a silent...Leave a comment:
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Troubleshooting PFC with SPC1012T not raising output
It has been a long while since I posted here to ask anything....hope you can help.
I have this Samsung power supply that uses SPC1012T as driver for the PFC and it's giving me a problem that I can't narrow down though I've troubleshooted and fixed hundreds of boards similar circuits.
I am attaching a schematic from a different Samsung board, but the topography is very very similar if not 100% the same and it uses SPC1012T, which BTW is a pinout match to UCC28063 for which there's plenty of information. I haven't confirmed they are functional equivalents, but I strongly... -
Re: I need bios eeprom LG 34UM68 EAX66876002
You get it off a working board.
More importantly, though, you most likely do NOT need it...you just do not know it yet.Leave a comment:
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Re: Samsung UN50NU6950FXZA ( All In One )
For anyone reading this thread I do not think you are on the right track looking into SLM4683A for the problem you describe.
The IC is an inverter driver as can be easily guessed if you look the area of the board it's occupying - it takes the rectified 13V output out of secondary of the main transformer and drives two MOSFETs , which in turn take power from another secondary through bridge rectifier.
I *guess* it may be possible for one to see what you're seeing with a certain defect in the IC, but what I've...Leave a comment:
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Re: Mitsubishi Lt-46164
Since we now offer repair for LT-46164 and the other main boards in the family I can clarify a few things to buy me (I hope) the right to post the below link:
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First (commenting on past comments) EEPROM failures are NOT at all foreign to those boards; they are not the most common issues, true, but they still do happen; they happen in later TV models as well, depending on architecture and design, so it is not like they are something that's left in the past.
NAND flash EEPROMs can get 1 single block corrupt and...Leave a comment:
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Re: Intermittent Power On LG 47LV5400-UB
I'd like to comment on that.
There are a few sellers out there who offer repair kits for practically any board they've heard of; if there are SMD capacitors they'll include them and if there are 1117 voltage stabilizes they'll likely include them too.
I have personally received customer's board with a vendor's repair kit consisting of capacitors and 1117 regulators that I have NEVER EVER seen fail on a particular Sanyo main board.
Simply put, there are a lot of vendors that are...Leave a comment:
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Re: Intermittent Power On LG 47LV5400-UB
Go straight to the main processor.
Board has a standby which rarely ever goes bad and main which BGA usually degrades and needs to be replaced.
http://www.coppelltvrepair.com/p/162...ausylhr-led-tvLeave a comment:
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Responding here, albiet with significant delay, for hopefully the benefit of those still in need.
We're component level service center for TV boards and since there's a particular shortage on market for particular board for The NS-P501Q-10A I am allowing myself to plug in here.
The two most common failures in NS-P501Q-10A are the X-Main LJ92-01688A and the Y-Main LJ92-01689A boards.
They fail independently from each other, just because of wearing out (yes, electronics wear out, due to thermal cycles of expansion and contraction of semiconductor...Last edited by SMDFlea; 04-09-2023, 04:37 AM.Leave a comment:
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Re: Vizio xvt472sv - PSON Always has Voltage
Just for the record, most of the times when a main board starts automatically (BL_ON activates almost instantly) 99% of the time the problem is in the main processor, which never actually starts up properly.
Seen it happen many times on various boards and for some reason always with MediaTek MT processors as opposed to, say, the Broadcom BCM ones.
- bobbyLeave a comment:
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Re: Vizio XVT423SV
1) Disconnect from AC, wait 2-3 minutes. Less if you disconnect main from power where DC is held by caps longer.
Hold down the rocker (power on) and connect the AC; wait until you see the "V" on the screen then release.
This, to the best of my knowledge, is factory reset settings for the family.
(you can also try it from the config menu, but as I understand this is better)
2) You can just replace the whole EEPROM on the main and all settings will get replaced along with it.
On a side...Leave a comment:
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Re: Difference Between BN44-00445a and BN44-00445c Power Supply
I do not mean to pick on you, but this is definitely an overstatement.
First, there are many different reasons for moving from one revision to another and not necessarily (or even mostly) finding problems in a given revision.
Second, nothing guarantees that the later revision will have less issues than the original.
In particular I've seen MUCH more BN44-00445C bad boards than BN44-00445A ones.
Note it doesn't mean the C is...Leave a comment:
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Re: Sony KDL-55NX720 blinks 4 times
Spent some time today troubleshooting a KDL-55NX720 with screen coming up for 4-5 seconds and then shutting off.
Haven't figured it out yet, partially because of Sony's idiotic design where if anything is disconnected (or failed) the whole TV shuts down and partially because, as usual, I was hacking and reverse-engineering my way around it without consulting any service manuals or schematics.
What I found today and what may help others in the unlikely event that I won't figure it out and the more likely that I don't...Leave a comment:
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Re: Dell w4201c hd pdp hdtv plasma tv
Just read that and I can't say I agree with it.
4 zener diodes in a row @ 5.1V each make zener of 20V.
They are on the sustain output where voltage is easily Vs at peak, i.e. over 100.
Have you actually tried putting 5V zeners there?
because I think they'll fry right away....Leave a comment:
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Re: vizio stuck on logo model m470nv
We've seen that happen due to bad EEPROM/firmware IC as well as because of a shorted HDMI multiplexor.
Both are available online for DIY repair , but both carry the risk of NOT being the source for the shutdown in your particular case. Although less likely, the main processor could also be bad, for example, as it is fairly complex and it may be able to start and execute the firmware all right, but a section of it handling the HDMI or LED driver control could fail to initialie/communicate with the core at a later initialization stage....Last edited by SMDFlea; 04-09-2023, 04:41 AM.Leave a comment:
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