I just picked up a Sharp LC-80UQ17U here in Denver on Craig's. The previous owner said he was watching it and "pop" it stopped. Opened it up to find a blown fuse on the high Voltage side of the PS. I bypassed it with a 7.5 Ampere automotive fuse and saw a flash in component NTC7001 (as the fuse popped). I am not going to try to apply any more power to the board until I can locate a schematic. Does anyone have the schematics to RUNTKB217WJQZ?
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hello pin AC_DET what condition is maybe is to hi -
It would appear as though some sort of schematic is on the back of the board. Is it safe to assume that these boards are single layer? Sorry for the DQs - I did avionics in the Navy but never at a board level.Comment
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Okay so here's a question for the experts. RL7001 on the back of the board (HF12FF marked on the relay package) is showing 300 Ohms or so on the relay coil but short across the switch contact. The datasheet for HF12FF doesn't show if its normally open or normally closed. The icon on the backside of the board shows open. It just so happens its adjacent to NTC7001 that gave off a small flash when I did my "fuse testing". Anyone have specific knowledge or experience with this part?Comment
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"The datasheet for HF12FF doesn't show if its normally open or normally closed."
Sure it does. It shows a normally open diagram, and the switch contacts will be closed when the coil is energized.
If you measured almost no resistance (0 ohm or exactly the resistance of your probes being touched together) then yes, it is shorted.
Most likely because the contacts have fused together, or just simply stuck. If stuck, you can try applying 12V DC to the coil and check if that will make them unstuck, if not then replace the relay.
Also, it is recommended when working with power supplies to use a DBT (dim bulb tester) so you won't end up with components blown to bits when there is still a failure in the circuit.
When the main fuse is blown, what you need to check first is always the bridge rectifier in diode mode, then the semiconductors in the primary side (more diodes, transistors or mosfets)
After the primary side is confirmed to be ok, then you can move on to the secondary side where the low voltages are.
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I second the dim bulb tester, easy to make for a few dollars, can check youtube for many how tos.Comment
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Holy Cow - this dim bulb tester is brilliant. What a great way to work on power supplies without roaching them. Heading to my Home Despot today to grab parts and build. Thanks all.Comment
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This MOV reads .86 MegaOhms in circuit. I have other PS boards that work with MOVs that are wide open this close to the fuse. Is close to 1 MegaOhm a defect? I have to think it is without any Voltage applied.
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If you can read the fine print on the varistor you can find out the spec, but you should measure its resistance out of circuit to get a better reading.
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hello check the voltage on d7950 (BU5V) or conect in this point extermla power supply an check if the main borad tour on the relay or the stnd by led is blinkingComment
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This TV is too huge and too expensive. I have decided to go with a repair service on eBay while I continue to teach myself SMPS circuits. Thanks for all the opinions here. I did indeed learn something even though its been 30 years since I left Navy electronics school.Comment
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The power supply board is very easy to remove, it is usually mounted by screws on a galvanized steel chassis inside the TV, and repairing it doesn't really need the TV at all.
Don't understand why the TV size and value would be a hindrance.
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It was indeed easy to remove and was fairly easy to diagnose to a degree. However, I cannot find the relay here in the US and didn't want to mess with it. I don't want to recycle this one as its huge, looks great and is extremely heavy.Comment
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On the relay contacts there is a low resistance thermistor in parallel for a soft start and it seems to you that the contacts are stuck together.Attached FilesComment
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I think that is true too. But I cannot source the relay so I sent the entire board out for repairComment
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.
The screen seems to blackout and stay black, but with a flashlight I can see the display.
With my Playstation 4 connected via HDMI, and running a game I can hear sound.
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I did not have any 27uf @ 50 volt capacitors but one nice thing is that it has enough room for two capacitors in parallel a 22uf and a 4.7uf @ 50 volts 22 plus 4.7 equals 26.7uf which so very close to 27uf I will show some pictures of it sometime tomorrow
This is one of the shit est boards I seen in a very long time and it was the daughter board the traces just lifting off the board I had to use the capacitor leads to repair the the traces and the main board is not any better because I had to repair several traces for the daughter board to the main board
After all of... -
Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic... -
Hey everyone,hope everyone is fine, I got an issue hoping you guys can help me,
I got a HP V193 monitor it has a E59670 now i got a few of these, been using them for long time now, however this particular monitor was blacking out for a few times then after unplugging and plugging it back in it gets back to normal until now its dead.
I tried switching the power supply board with another similar monitor and it works,so I'm trying to fix this power supply board I got some basic in electronics as a hobbyist.
Steps taken so far:
Checked all...02-21-2023, 04:00 AM -
Hello, I came here after finding some similar questions asked on other monitors and hope someone here can help me get an ancient Viewsonic VP230mp (23" 4:3 LCD) back to working condition.
First a little background, I have a background in computer and electrical engineering, and I'm smart enough to know I know nothing about LCD displays and how they work. For this topic I'm as green as they come.
When the display is turned on the viewsonic logo displays in the uppper left for 2 seconds then the screen goes black, the power LED is green (on) and when a computer is connected...
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