Re: 12V rail is not on ?
You need to learn how to read the spec sheet.
Is the tester testing at the 'TEST CONDITION'.
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Re: 12V rail is not on ?
You need to learn how to read the spec sheet.
https://cdn.badcaps-static.com/pdfs/...a4e657e4a3.pdf
Is the tester testing at the 'TEST CONDITION'?
And which 'C' is that the tester referring to?Last edited by budm; 10-13-2016, 08:54 PM.Leave a comment:
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Re: 12V rail is not on ?
and bad 2SC5763 as well...hfe = 18...minimum 20Leave a comment:
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Re: 12V rail is not on ?
I got bad 2N60, C = 1.06 nF...on the datasheet, maximum = 350 pFLeave a comment:
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Re: 12V rail is not on ?
It looked like you had unsoldered a capacitor next to C17 and diode D7 (next to 5VSB wire). But if you didn't then that's perhaps how the PSU came (I wouldn't be surprised.)
That said, those burned resistors are typically a result of 5VSB over-voltage or 5VSB regulation going bad. This happens if the output capacitor(s) on the 5VSB rail fail, the "critical" 5VSB cap on the primary side fails (typically it's a 10-47 uF, close to the 5VSB transformer... looks like possibly C8 in your PSU), or if the 5VSB is ran without output capacitors. Hence why I thought you had removed it.
Either way, before you even try to do anything else in the PSU, first the 5VSB rail must be fixed and working and showing 5V +/-0.25V at most. Then you check the standby secondary auxiliary rail (can be measured at one of the didoes next to 5VSB transformer on the secondary side, possibly D9, D10, or D12... one way to recognize it is to look on the trace side of the PCB and see which diode is connected to a pin on the 5VSB transformer.)Leave a comment:
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Re: 12V rail is not on ?
which capacitor are you talking about ? I never unsoldered it...Leave a comment:
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Re: 12V rail is not on ?
I see missing electrolytic caps on the 5VSB line. Did you by any chances plug in this power supply without those caps? If yes, that usually causes an over-voltage on aux. secondary side of the 5VSB transformer, and probably the reason those two resistors burned.
Point in case: do NOT test electronics with capacitors removed.Last edited by momaka; 10-11-2016, 10:19 PM.Leave a comment:
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Re: 12V rail is not on ?
35VDC is the gestimate Voltage, the cap is rated at 50VDC.Leave a comment:
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Re: 12V rail is not on ?
So 2005 needs to be replaced, I reckon...
power dissipation is P = V^2 / R = 35^2 / 1K3 = 0.942 W, that's why it was burned...how do you get 35VDC from ?
Yes it's rated 1/8W, I've replaced it with 1/4W, but I haven't changed 2005 chip, not yet arrived...Leave a comment:
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Re: 12V rail is not on ?
"I tested the resistance from pin 7 and 8 to GND = 300 ohm..." That cannot be right, they are way too low. So lets say that the Supply Voltage is 35VDC, that means the current through 1K will be about 27mA and most Vdrops will be on the 1K resistor so the power dissipation for the resistors will be about 3/4 W, those 1K resistors are rated 1/8 W or more if the supply Voltage is higher than 35V.Leave a comment:
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Re: 12V rail is not on ?
To have those pull-up resistors burnt up, it must have lots of current flowing through them to GND return, one will be the Drive output pin 7 and pin 8 are shorted out to GND pin of 2005, or the B-E junction of Q5, Q6 through D19 to GND.
You should verify first if those two resistors are connected to pin 7, pin 8 of the IC, then check the resistance between GND pin and pin 7, pun 8.
BTW, one thing we know based on the diagram, the filter cap is rated at 50VDC so the supply could not have been more than 50V.Last edited by budm; 10-10-2016, 10:31 PM.Leave a comment:
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Re: 12V rail is not on ?
R34 and R33 suppose to be 1K ohm....I don't know what the value is after burned....could be shorted..Leave a comment:
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Re: 12V rail is not on ?
those resistors are related with 2003 straight away....I'll test the transistor near by (Q5 and Q6) and show you the result...I reckon they are ok, but 2003 has a problem...Leave a comment:
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Re: 12V rail is not on ?
Just now, I saw two burned resistors....near to 3.3V rectifier....I'll show the pictures...hold on...I'll take picture of them...that's why I saw a smoke yesterday, and it was resistor burn smell yesterday, but haven't seen it yet until now...R33 and R34Last edited by bianchi77; 10-10-2016, 09:50 PM.Leave a comment:
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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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