Re: lenovo G550 zombie laptop.
Check the Close Lid switch to resolve the backlight.
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Last Activity: 02-04-2022, 02:00 AM
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Re: LG 1918s No power
Oops i was measuring AC on the large cap.
Large cap has DC Voltage 345V, ALL caps have been replaced except those two small starter caps. Yes i am aware of the irony that the monitor won't start and i have not replaced the starter caps. They are not currently on stock and will replace them when they are available.
Here are the pictures:...Leave a comment:
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Re: LG 1918s No power
Thank you for the replies,
We have 230AC here so i set the dmm to 750V AC and messured the leads on the large capacitor. No volts.
I thought it was the transformer clicking but i could be wrong, sound is coming from that area. I will post pictures tomorrow when i am able to access the monitor.
Diode checked the bridge rectifier - no shorts and no reverse current flow
Thermistor looks ok but i forgot to test it. That would explain the problem i think.
Thank you for the answers, i will...Leave a comment:
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LG 1918s No power
Hello,
Sympoms are:
No power on
Transformer clicking
Diagnosys and Tests:
No 5V VSB
No voltage on large cap 100uf 450V
Bridge rectifier OK
Mains fuse OK
0.47uf capacitor OK
ALL caps look OK but not replaced
My main concern is why is there NO voltage on large cap?? Can somebody please shed some more light on this case?
Thank you -
Re: Problems with Samsung 740N monitors
Thanx for all the help guys!! Even if i fail to fix this thing, im really happy that i found this forum. So much to learn here. If i find a solution to my problem i will post it, but i will not post anymore questions.
Big thanx again to allLeave a comment:
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Re: Problems with Samsung 740N monitors
750V was due to a broken DMM
i forgot to mention that later.
1. Line voltage here is 230V AC
2. & 3. I disconected the fuse to the inverter and the green transformer is making less noise and does not stop working (when the fuse is in place, transformer is working for 2 sec then stops working, then starts for another 2 seconds...)
4. DMM Velleman DVM 760, ESR meter
13V and 5V line was measured on CN2Leave a comment:
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Re: Problems with Samsung 740N monitors
Thanx for all the help so far. Yes, they were all Capxons. Caps definately arent the problem. Thats the third set of caps in this board
.
Leave a comment:
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Re: Problems with Samsung 740N monitors
Sorry for the late answer, i was sick these couple of days.
Still no improvements, I replaced ALL capacitors from a working 740n monitor and i still cannot find the problem. 5V line is ALWAYS ok. As soon as i turn it on, 5V line reads 5.1V and stays that way. All resistor have been checked and they have the same value as the working one. I am starting to think that the big green transformer is the problem, because every other part has identical readings as the working monitor.
Can i attach an external power supply to...Leave a comment:
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Re: Problems with Samsung 740N monitors
Still no luck,
i detached the 3A fuse so the inverter wouldnot startup a did everything you said Wizard. All resistors check out, and yes, on tl431 there is 2.49V. I am using low ESR capacitors and i still dont have a clue what is wrong. Do u have some other advice i could try? I would hate to throw away this monitor for a problem that maybe cost a few bucks.
I noticed that voltage dropped to 16.30V when i removed the 3A fuse. Is this information helpful?Leave a comment:
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Re: Problems with Samsung 740N monitors
You guys here are quick. Didn't expect a reply so soon.
I replaced all caps again and no luck. I put in 3 CapXon 25v 1000uf. I did that on my friends monitor and his is working like a charm. Mine just wont stay on. Itried 2 1000uf + 1 470uf and the problem remains.
1. I turn the monitor on,
2. Big green transformer starts to make hissing sound and 13V line reads 18,3V
3. Lamps go on for a split second, 13V line reads 10-13V
4. Big green transformer stops making noise and lamps turn off...Leave a comment:
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Re: Problems with Samsung 740N monitors
Greetings to all
I have changed 3 820uf capacitors and 3A fuse and now the CCFL lamps start for a second and they turn off again. After two seconds they startup again for a second and turn off again. I checked 13V line and it reads 18V and just as the lamps turn on for a second voltage drops to 13V and comes back to 18V when the lamps turn off. What can be the problem?Leave a comment:
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