Re: 12V rail is not on ?
Which link ?
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Re: 12V rail is not on ?
Umm... that link isn't showing.
With your DMM set to diode mode, probe the left and right pins of the diode to the middle pin. If there is a short, the diode is bad. easy.
The SBL1040 is a 40V, 10A Schottky rectifier that has a voltage drop of 0.6V. Problem is that it is only a diode with 2 legs, it should be one with 3 legs.
Maybe you can upload nice straight shot, high resolution pictures here to badcaps, using the attachment feature.Last edited by CapLeaker; 07-21-2016, 05:58 AM.Leave a comment:
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Re: 12V rail is not on ?
Almost the same with :
"LC-B250ATX ch. Y-B200-ATX ver. 2.9 JNC Computer Co.""
I can see diode label is match...Leave a comment:
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Re: 12V rail is not on ?
Looks like it's different from the schematic, since it's not D8...Leave a comment:
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Re: 12V rail is not on ?
Are they all faulty ? I measure from new diodes 0.6VLeave a comment:
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Re: 12V rail is not on ?
Diode in the middle is connected to 12V rail...
and I measure with diode 0.1V both side from the base...
and the left and right diode SBL1040..
I got only 0.4V left and right from the base...
Leave a comment:
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Re: 12V rail is not on ?
Don't switch the PSU on after removing components. Just test them for shorts without powering on.Leave a comment:
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Re: 12V rail is not on ?
C27? Is it possible I break other rails?Leave a comment:
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Re: 12V rail is not on ?
CapLeaker has already identified the components that are likely culprits.
In any case you appear to have already found the problem -- shorted D8. After removing D8, test for shorts across the 12V output again. Also confirm that D8 tests shorted out-of-circuit. There should be an electrolytic capacitor filtering the 12V output. Test it also.
Edit:
Here is the circuit diagram for an LC-B250ATX.
"LC-B250ATX ch. Y-B200-ATX ver. 2.9 JNC Computer Co.""
https://cdn.badcaps-static.com/pdfs/...83951b6882.pdf
Some time ago I had a fake 400W PSU which was actually a 200W version of the above circuit:
http://www.electronicspoint.com/thre...atabase.132952Last edited by fzabkar; 07-21-2016, 12:14 AM.Leave a comment:
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Re: 12V rail is not on ?
If there is a short between 12V and Ground, then isolate the relevant components on the secondary side until the short goes away.Leave a comment:
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Re: 12V rail is not on ?
I tried common an ps_on..no response only can hear high pitch noise...Leave a comment:
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Re: 12V rail is not on ?
Got it..small 22nF near the chip..is that Pwm switching chip?Leave a comment:
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Re: 12V rail is not on ?
Can t find C26? Is the schematic the same between 250w n 300wLeave a comment:
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Re: 12V rail is not on ?
5VSB is always on. I am guessing that is the only thing that is powered up. No -12V, no +12V, no -5V,no +5V neither the +3.3V. To turn the rest of the PSU on, take a 1k resistor and jump 5VSB to PSon.
Other than that, check that D8 isn't shorted, T4 has continuity between pin 5 and 6, L6 isn't open, and that C26 isn't shorted to GND.Last edited by CapLeaker; 07-20-2016, 06:10 PM.Leave a comment:
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12V rail is not on ?
Guys,
Does anyone know why my 12V rail is not on ?
5V standby is on....
The power supply is LC 300ATX, does anyone have the schematic ?
I suspect my 12V rail is short, because of short on my capacitor on motherboard..
it's using to diodes soldered together into heatsink...is it FR302 ?
I saw :
http://danyk.cz/s_atx05a.png
Thanks
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Hello everyone,
I'm trying to repair my old Acer Nitro 5 (AN517-54-55T5). I've already bought a new laptop, so this is more of a learning project. For the experience, with no high expectations of success.
Well, my decice specs are the following:
Model: Acer Nitro 5 AN517-54-55T5
CPU: Intel Core i5-11400H
GPU: NVIDIA GeForce GTX 1650
Motherboard: GH51G LA-L181P Rev:1c
The symptom:
When pressing the power button, the power LED lights up for about 5 seconds and then turns off. Initially, the issue was intermittent: sometimes...05-26-2025, 10:49 AM -
Hello,
Have an Xbox One S here that has a short on the 12V power rail. There is no power, beep, or partial fan spin when connecting power cable.
After diagnosing with thermal camera, Q9F1 MOSFET (NTTFS4C50N) is getting hot. When I remove this MOSFET, the short on the 12V rail disappears.
I first replaced Q9F1 with one from a donor board and then partially reassembled the Xbox to test. When I plugged the power cord in, I got a partial fan spin and I thought I had fixed it, but unfortunately, the Xbox still did not power on. So I then disassembled the Xbox... -
Hello everyone!
This grafic card came for repair, but when I connected it to the motherboard, the board would not start (short circuit in the 12V rail).
After removing some PLs to isolate the short in the 12V rail, I got to PML1/PML2, according to the BoardView reference.
Even injecting a voltage of 1V0 and a current of 3A in the FBVDDQ rail, for example, the voltage drops to 0V20 and none of the components heat up.
The attached boardview file is very similar to this grafic card, which I am basing the repair on.
I would like some...05-10-2025, 09:19 AM -
Hi all.
This notebook was showing no signs of life.
I removed the FH52M LA-J891P mainboard and found that there was 19V at the DC jack.
However there was zero volts on the two PRB2 and PRB46 resistors immediately after the two polarity protection MOSFETs (PQB11 & PQB12).
If I remove the PQW1 MOSFET, the 19V rail starts working, and I can turn on the unit - at least I get the fans, and the power light comes on, when I simulate the power button being pressed. No display.
I tried replacing the MOSFET with a new one, but again no voltage on the... -
Hello,
first of all I want to apologize for my bad English, but I try to give my best.
Customer brought me a laptop, which is charging the battery (when the dc-jack is connected) but don't power up when the power-button was pressed down. Only the white LED lights up, and you can hear a short noise in same interval when power-button was pressed and hold for longer timer. The customer changed already battery and dc-power-adapter.
For this laptop the correct shematic is the service manual "Clevo NH50ER NH57ER NH50EPS NH57EPS - 6-71-NH5S0-D02 Schematic"....
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