It's alive under load! I couldn't have done it without all of you, I learned a lot from this little detour. I feel a lot more confident approaching power supplies now. Big thanks to [B]прямо[/B], [B]Per Hansson[/B], [B]CapLeaker[/B], and special thanks to [B]c1q3[/B] for getting the ball rolling in the beginning. Sorry trash can, but you're going hungry today! 😉
Just a quick recap of everything it took:
TNY284 chip for 5VSB
Fusible resistor
15V Zener diode
2 transistors
CM6500UN PFC chip
all because someone dropped a screw in the...
hobostove
Senior Member
Last Activity: Today, 10:15 PM
Joined: 05-08-2023
Location: Austin, TX
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It was my crappy tester again, loose connection. I think it's time to retire it. 12V is present after all! Next step now is to load it and see what happens 🤞Leave a comment:
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Anyone have some guidance on where to start tracking down why 12V is missing? I have 5V and 3.3VLeave a comment:
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Alright, new PFC chip arrived. Put it in, and now seeing 375 on the main cap. Tester stays on steady now, but no 12V yet. More to do!Leave a comment:
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I used AON7380. I ended up finding the first DC-in mosfets were short. Once I replaced those the low charging mosfet survived. It's charging now.Leave a comment:
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I found the low side mosfet PQ706 was shorted. I replaced it with one that tested good, but that one went short immediately. I tried another, and same thing, shorted. There's no short on the board. What could be killing these mosfets?Leave a comment:
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Okay, ordered another battery to rule that out.
The battery is at 11V right now. When I add AC power, the battery connector goes up to 19V briefly, then settles down at 11.5V, but it's not taking current. Taking off AC power, and it goes back down to 11V. I replaced the BQ chip.
I'm thinking one of the mosfets?
Datasheet: [URL]https://www.badcaps.net/forum/showthread.php?t=74069[/URL]https://Okay, ordered another batter..., then settlesLeave a comment:
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Looks like that resistor was in series with VCC going to the PFC IC. PFC IC is shorted. VCC pin is 3ohms to ground with the chip off the board. 5VSB is back with the chip off. Going to order one. I'll be back in a weekLeave a comment:
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Found an open resistor near the PFC IC, has a hole in it. Replaced it and now 5VSB is shorted again. Getting there!Leave a comment:
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What's the model of the power supply?Leave a comment:
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PFC OUT signal looks like this on the scope, pretty much nothing
[ATTACH=JSON]{"alt":"Click image for larger version Name:\timage.png Views:\t0 Size:\t303.1 KB ID:\t3615946","data-align":"none","data-attachmentid":"3615946","data-size":"full","title":"image.png"}[/ATTACH]...Leave a comment:
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The transistor that was shorted was Q3 on this typical application schematic for the PFC IC (CM6500UN). I replaced it last week and the short is gone. Maybe the PFC chip is dead?
Worth noting the schematic here shows one mosfet, this psu has two. Also, I'm missing the 10ohm resistor and diode between the transistors and the mosfet gate. I do have the 10ohm leading back to PFC OUT though.
[URL]https://www.kediman.com/attaches/2017/04/906-vempt0.pdf[/URL]
[ATTACH=JSON]{"data-align":"none","data-size":"full",&q...Leave a comment:
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Both led pins of that optocoupler are indeed high. I think I follow now. If the supervisor IC is happy, it'll open a ground path for that led. If it's unhappy, it'll disconnect itself and the gnd side of the LED is normally pulled up somewhere.
I get 167V on the main cap, so next step is try to work out what's wrong with the PFC I suppose.
Going back a bit, before I got 5VSB to come up, I had to solve a short. Looking at it now, it was a transistor headed into the little PFC daughterboard. Probably more than coincidence. I'm looking at that area now.Leave a comment:
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FPOB is high @ 5V. Datasheet says it's an open drain. Shouldn't it go low if the protection is tripped?...Leave a comment:
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10.2V then it shuts down
12V
[ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3615126}[/ATTACH]
5V
[URL=filedata/fetch?filedataid=380451][ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3615125}[/ATTACH][/URL]
3.3V
[URL=filedata/fetch?filedataid=380450][ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3615124}[/AT...Leave a comment:
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I attached a load (3 old 3.5" drives), and now it's shutting down immediately and staying dead until it's left unplugged for a few minutes.
So definitely seems like protection mode kicking in. Maybe without a load 10.8V was just near the threshold of an undervolt condition, and with the load it droops into a definite protect.
Datasheet seems to agree.
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3615112}[/ATTACH]
...Leave a comment:
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Alienware 17 R4 LA-D751P - Battery Not Charging
Was water damaged (pint of beer). I've been messing with it and it's mostly up, but there's an issue with the battery not charging.
The original was DoA, so there's a new one in there now. On the bench psu, measuring the battery connector (battery is 15.2V), the connector shows 16V and 9A on the 19.5v psu!
This lasts a second or two, then it settles down to 14V, 0.06A. Unplugging AC power and it shows 13.5V. Do we think battery or board (BQ, Mosfet, etc)?
[URL="https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/schematic-requests-only/67224-looking-for-schematic-for-la-d751p-motherboard?t=74069"]Link... -
Adding some photos here
[ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3612206}[/ATTACH] [ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3612207}[/ATTACH]Adding some photos here
[ATTACH=JSON]{"data-align":"none","data-size":"medium","data-attachmentid":3612206}[/ATTACH] [ATTACH=JSON]{"data-align":"none","data-size":"medium",&q...Leave a comment:
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Nvm, I have 12v1 and 12v2, tester connector was a little loose. However, they're only 10.8V. And after 10-15 seconds I can hear a relay click and the supply shuts down....Leave a comment:
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I found a shorted transistor on the hot side with a thermal cam. Replaced it and 5VSB started up. Now I can see that I'm missing 12v1, and 12v2 is at 11V. 3.3V is fine. Time for more troubleshooting!Leave a comment:
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