Ripped off a trace and pads when removing the transformer to get to what i thought were two heatsink-mounted diodes, but they were mosfets that had their third leg soldered to the heat sink
They both tested good as mosfets
Board's very bent
Over it...
It's now a parts PSU now
Maybe someone can add to this topic if they make any further progress with one of these
socketa
Asbelowsoabove
Last Activity: 06-09-2025, 01:43 AM
Joined: 06-18-2014
Location: hell
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Q27 and Q28 were shorted D-S,
which placed shorts across the other two non-shorted mosfets Q26 and Q29
Additionally, after removing the solder and disconnecting a leg, it looks like one of the rectifying diodes is open, as i get no response from it on multimeter diode test mode - this connects to the 5V rail via a 2 Ohm resistor, which, as mentioned before, is unexpectedly connected to the gate of Q29.
Neither he gate of Q29, nor it's series 2 Ohm resistor, are connected to any of the pins of the 6601 FSP controller chip...Last edited by socketa; 11-16-2024, 02:44 PM.Leave a comment:
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3.3V and 5V rails are shorted to ground,
so that's probably what's causing the transformer to squeak
also, testing across all four mosfets, in circuit, that are on the back of the PCB, the drain and source are all shorted to groundLast edited by socketa; 11-15-2024, 08:20 PM.Leave a comment:
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Was checking the other side of the 10K ohm resistor AC with a multimeter and was just about going to connect the scope, but before that i powered on the PSU few times and one of those mosfets blew up with a bang and a spark.
Talk about Murphy's law...Twice!
I took a chance, and replaced the mosfet
(The mosfet that's next to it looks damaged, but that was just some surface damage that happened when i was removing it earlier on)
So now after checking with a scope on both sides of the resistor...
the side that is connected to the chip displays an /| /| /| waveform, of...Last edited by socketa; 11-09-2024, 04:44 PM.Leave a comment:
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Thanks for you suggestion,
Yes, that did cross my mind.
I have a scope
... and thought that that might be a good option, but wasn't sure about it, so decided not to, since i don't want a high voltage to damage the scope
Also i may have tried connecting a multimeter on AC, and didn't see significant voltage; so that might have discouraged me?
Now the PSU as gone back to the fan briefly spinning... but now with an additional short, mouse-type, squeak that's coming from the main transformer 😠(used a small rubber hose to pinpoint the area)
I checked the rectifying...Last edited by socketa; 11-09-2024, 02:24 AM.Leave a comment:
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Checked the temperature of the chip, the pin of the chip that's connected to the 10 ohm resistor, and the PCB near the resistor; but the resistor is the hottest.
How can a resistor heat up like that with such a small current?...Last edited by socketa; 10-26-2024, 05:07 PM.Leave a comment:
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Checked the voltages at either side of the diode:
12.15V at the cathode, and about 11.6V at the anodeLeave a comment:
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Working good now
Except the 10K resistor heats up to more than 100 [B][URL="https://www.metric-conversions.org/temperature/fahrenheit-to-celsius.htm"]°C[/URL][/B]
Couple of youtube vids of folk replacing this resistor that had obviously burned out due to to excessive current, but they failed to check the temperature
Over 1M ohm at the resistor to ground, and the only other path that's connected to the resistor (except for the SMD caps and the FSP chip pin) is a diode that has 47K ohm to ground on it's other end.
This diode (D1) is biased for current flow into...Last edited by socketa; 10-26-2024, 02:22 AM.Leave a comment:
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So it looks like it's probably the same fault
I've put it back together and will order replacement mosfets, and then try using a 10 ohm resistor (post #24)
The output caps tested good ESR and resistance (couldn't read two of them because i pulled out the leads when removing them)Last edited by socketa; 09-28-2024, 06:35 PM.Leave a comment:
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I just destroyed one of these that had the same symptoms
​After a lot of effort getting the large toroid off, i saw that the gate of 031N03L (Q29) goes to one of those 2R0 resistors, and then to that through-hole dot, then through the board and onto the top side of the board to a trace that goes to through-hole dot that is between the two mosfets (G26, Q27), which are connected to both big square pads, which are connected to the 5V rail
So it looks like the gate of Q29 is meant to be connected to the 5V rail via a 2R0 resistor
Gate Q29 ----- 2R0 ----- 5V...Last edited by socketa; 09-28-2024, 01:13 AM.Leave a comment:
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[ATTACH=JSON]{"data-align":"none","data-attachmentid":"3331302","data-size":"thumb"}[/ATTACH] Removed the south bridge and, unfortunately a couple of pads 😢
If i replace the pads, will UV-curing conformal coating cure if it's underneath the pad, so that it secures the pad?...Leave a comment:
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That was probably because i put the chip back on the wrong way around
... to be continuedLeave a comment:
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Since my diagnostic card wasn't showing any readout, i figured that the BIOS wasn't being read.
Flashed it, but the board still doesn't POST
There is a hard short to ground on the BIOS Vdd power supply pin,
Which could mean that the chip is faulty (which is unlikely since i had no problem flashing it), or there is some shorted component.
I checked a couple of schematics of similar boards, and the BIOS chips are powered directly from the 3V or 5V rails...hmmm,
But the 3V or 5V rails are not shorted to ground on this boardLast edited by socketa; 08-12-2024, 11:01 PM.Leave a comment:
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My Hipro HP-D3057F3H only had 2.6V on the 5VSB
The fault was due to 5ohm ESR on one of the non-bulged Teapo SC 1000uf output caps; so i guess that the Viper22A detects overcurrent, and goes into a low power mode
BTW, this PSU has a tricky (for me), unusual, feedback circuitry on the 5VSB: The Viper22A is connected to the first optocoupler, of which the secondary side is earthed, and which is turned off or on by one of the TL431 shunt regulators (there's three on the secondary side of this PCB), which is connected to the adjacent optocoupler.
Also, in terms of being able to remove...Last edited by socketa; 07-30-2024, 04:48 PM.Leave a comment:
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Ok, so i lifted the three legs of the PWM controller, and there was no voltage on it's OUT pins that are going to the three drivers, even when shorting the VID pins to ground.
Then i put the overclock chip back in, and there is the same voltage on each of the PWM controller's OUT pins (50-250mA - it changes each time that i power it up)
Shorting the VID pins to ground makes no difference.Last edited by socketa; 02-08-2024, 04:05 AM.Leave a comment:
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Removed the overclock chip, so it's VIDOUT pins are definitely disconnected now
But lower mosfets still don't turn on when shorting VIN pins to groundLast edited by socketa; 02-07-2024, 10:27 PM.Leave a comment:
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Yes, i disconnected the PSU and moved the CMOS reset jumper to reset position and then back again
I also flashed the BIOS because it's checksum had changed
So even though i ground the VIN pins that go to the controller which tell it what voltage to regulate at, there seems to be something disabling the chip from outputting signals to the drivers,
Like you say, maybe the overclock chip is telling the controller chip to not output, irregardless of whether i try to force VCORE by grounding the VID pins
I found a schematic of a board with that overclock chip
[URL]https://elektrotanya.com/gigabyte_ga-8knxp_rev_2.0_sch.pdf/download.html[/URL]...Last edited by socketa; 02-02-2024, 01:32 AM.Leave a comment:
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Maybe due to this?
Top right and bottom right
[URL=filedata/fetch?id=3208398&d=1706775733][ATTACH=JSON]{"alt":"Click image for larger version Name:\ttop right near lever..jpg Views:\t14 Size:\t50.5 KB ID:\t3208398","data-align":"none","data-attachmentid":"3208398","data-size":"small"}[/ATTACH][/URL] [URL=filedata/fetch?id=3208421&d=1706777047][ATTACH=JSON]{"alt":"Click image for larger version Name:\tTop left.jpg Views:\t0 Size:\t59.0 KB ID:\t3208421","data-align":"none","data-attachmentid":"3208421","data-size":"small"}[/ATTACH][/URL]...Last edited by socketa; 02-01-2024, 03:30 AM.Leave a comment:
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The VID pins of the VRM controller chip are direclty connected to the VIDOUT pins of the jumperless overclock chip
It seems like the job of the overclock chip is to override the voltage that the controller chip is putting out.
Shorting pins VID 3&4 of controller chip to ground should give 00111 (1.35V)
But this new PWM controller chip is also not sending out any PWM signal voltage to the drivers.
The three driver chips each have 12V power at VIN, and voltage on drains, and the controller chip has PGood voltage,
and the jumperless overclock chip correctly detects...Last edited by socketa; 01-31-2024, 11:38 PM.Leave a comment:
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Well, it looks like that VRM controller chip was possibly OK
because i replaced it, and there's still no voltage on it's PWM out pins, even when grounding the VID pins (which are all high)
so no Vcore
and the board won't shut down using the power button...Leave a comment:
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