After some troubleshooting I found the culprits, missing FB, FBRTN, PWRGD which makes the VRM not switch (no PWD 1-4 voltage). FB and FBRTN are all connected to their respective rails. Injecting FB makes PWRGD still stay low....
Injecting Vcore directly onto the coils makes the CPU get out of reset, but it's still not posting...
All I know is that the ADP3168 sees some unknown fault and halts the switching of the VRM and that's it.
Any ideas?
kotel studios
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Last Activity: Today, 09:23 AM
Joined: 12-09-2024
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Intel D865PERL - no Vcore after replacing MOSFETs and MOSFET drivers
Hi,
Finally got time to fix this board up.
At first it didn't give any POST codes. Turns out it was an unsupported Celeron D cpu. After dropping in an Celery 2.6gHz the CPU came out of reset with clock signal, but still no post codes. For a while it did work when I applied pressure to the ADP3168 chip, but on next reboot the MOSFETs started to burn. Then I left it as is for months.
Now I came back prepared. Replaced the bad MOSFETs and the ADPxx18k drivers. Now I don't get any MOSFETs blowing up issues anymore. But sadly, the Vcore is missing. The whole VRM isn't...Last edited by kotel studios; 04-22-2025, 06:16 AM. -
Okay under general load (as I would run it) the cpu 12.8v goes down to 12.66v and [i]seems[/i] to be going slowly up. So ig it should do the trick.
Generally this whole repair could've been avoided if I cleaned this PSU and waited like 6 months before testing it without a sacrificial board.Okay under general load (as I would run it) the cpu 12.8v goes down to 12.66v and [i]seems[/i] to be going slowly up. So ig it should do the trick.
Generally this whole repair could've been avoided if I cleaned this PSU and waited like 6 months before testing it without a sacrificialLeave a comment:
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Okay, since everything seems to work fine I decided to rework the case a bit and guess what? The 4pin CPU power is proprietary. Instead of 12v or 12.4v high power it's 12.8v (no load is 13.20v while with an 12v 5w bulb it's 12.9v)...
I'm not gonna write about "downgrading" the rail here since this post was just to fix the screeching noise.Leave a comment:
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UC3845B PWM chip. I think it was ground with output shorted. Gotta recheck once I get to finalization of this repair.Leave a comment:
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Yep, it was the short on the dip 8 component at fault. Or that and the out of spec 220uF 25v cap. Odd since there wasn't any short before on it.
Now the PSU works without any fuss with the original caps. I will do further testing to confirm whether this PSU is safe for normal use.Leave a comment:
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Actually, after removing all of the transistors I noticed the dip8 component on the primary side had two legs shorted. Odd, don't think I've done that while desoldering the transistors and whatnot...
And now after putting everything back together I get no life at all from this PSU. Not even the bulb protection. I guess the 230vac wires got screwed.Leave a comment:
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Overloading shouldn't be the issue. The board takes waaaay less than 180W the PSU is rated for.
Old caps in and the original fan and still the same issue. 12v is 11.84v.
I think the sound comes from near the transformator. If it had shorted windings then the PSU wouldn't start up right?
I will need to pull out the transistors near it and check them out of circuit (in circuit they are fine).
I am running out of ideas now. I should also replace all of the smaller caps on the secondary side, but who knows if that'll help....Leave a comment:
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Primaries were replaced but the sound is still there..... So this can't be the primary side. Gotta take a closer look at the secondary or better yet, put the original caps in....Leave a comment:
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Okay still same sound, even after replacing an 10uF 50v cap connecting to 5v rail (I didn't see that one of the legs was broken). Maybe even worse. This time I measured 5v rail and it was 5.14v
Another idea would be that the primary caps are cooked and need to be replaced, but the only 470uF 200v caps I have report as 320uF which is not normal (they are from an LC clone). I think for testing they should be enough.
Any ideas?Last edited by kotel studios; 03-26-2025, 09:07 AM.Leave a comment:
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I don't think it's the first assumption since I used the same caps as with my LC clones, but who knows what hp did with their stupid engineering.
lcr t2 tester. Sure, it's nor that reliable but it gives me an rough example of what the real capacitance should be. ESR is always 0ohm (tester limitation) and V loss is either 0.2% or 0%.
...Leave a comment:
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Compaq PDP-124P - loud screeching when running
Hi,
Recently I got my compaq PDP-124P to "work" and it now screeches loudly when running (you can hear it from 60cm away!).
There's nothing shorted on it, caps were already checked and replaced when they were close to being above 20% of rated spec, apart from the primaries. Fan isn't the issue too.
I didn't have time to measure the voltage rails (beside 12V, that one had 11.7V) due to the unexpected sound.
Load was only an single sacrificial board w/o CPU power since these PSU's don't work without mainboards.
Any ideas what could be... -
That would indicate the coupling caps being bad. Recheck them if they are okay....Leave a comment:
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Okay it was another 230v cable connecting to the board doing all this wonky stuff. With it replaced the PSU runs stabely enough. No funky smells or anything.
Secondary heatsinks get around 54C warm after running with 5 3.5" HDD's and an mainboard without CPU connector in place and an 12v 35W bulb on 5v/12v rails for around 10-20 minutes.
I guess this is another repair finalized without the optional compaq PSU which shocked me wit an bright white arc from it.
Many thanks to[B] [URL="https://www.badcaps.net/member/6996-momaka"]momaka[/URL][/B] for helping...Leave a comment:
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Okay and more weird stuff.
Now after putting the sec aux rail diode back in the PSU can start with the original rail? Although there's an weird high pitch sound coming from somewhere primary to transformator side. And it's not the fan (I have unplugged it for funky smell testing).
[s]Maybe the BJT's burning? I don't have any more left of them so I don't wanna risk burning my last working pair out....[/s]
Turns out it was the 3.3v buck converter coil. Redone the solder on it and the smaller coil near it on the 3.3v rail and the noise is gone and the PSU never died so far from...Last edited by kotel studios; 03-19-2025, 08:51 AM.Leave a comment:
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Huh, this is weird....
So I redone the same test again and no wonky stuff. I have upped the voltage to 3v and I only heard the relay sound. And since I didn't have anything left to lose I upped it to 4v and spam-shorted the PS_ON (with the relay sounds). And guess what?
[B]It works[/B]. 5V rail is generating proper (5.04v). Weird how when I turned off the power to the sec aux rail (my bench PSU) the excellent was still running (4v reading from my MM)...
Anybody that could tell me what the hell is happening here?
EDIT: I was dumb and I was shorting the PS_ON...Last edited by kotel studios; 03-19-2025, 05:11 AM.Leave a comment:
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So I found something weird out. When I desoldered the anode of the sec aux rail coming from the transformator I now see 1.7V on the rail. I also hear some weird sizzling noise which sometimes appears and a funny smell follows. There wasn't anything shorted.
Now I am more keen on transferring over the parts from this to the LC PSU board. In fact I might actually start the transfer today.
As for the destructive test I think it's better to leave as a last resort [i]if[/i] the frankenstein excellent power/LC PSU won't work.So I found something weird out. When I desoldered the anodeLeave a comment:
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I have done measurement error. I have accidentally put the probe at 5VSB anode, not sec aux rail cathode....
I get 16.41V in the correct spot
I think that is [i]way[/i] too high.... Might be wrong since the all the lythic craps were changed. But nontheless other components might be screwed, but still, above 16V to drive the primary BJT's is too much IMO. I'll try to cut the power to sec aux rail and inject voltages starting from 7V to 9V (emmiter-base max voltage) and if that doesn't help up to 12 or 14v.I have done measurement error. I have accidentally put the probe at 5VSB anode, not
Leave a comment:
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Okay so I have risked seeing the diodes go sparky spark and applied power to the PSU (with the bulb protection). And it's back to the half-dead state....
I guess we could only drive the primary side with one from another PSU
[B][I]Or[/I][/B] we could go the screwery way with success chances bellow 50% and put the excellent power parts into the LC board and hope nothing else was screwed, which now it seems there is something badly screwed.....
On further inspection I see there's only 1.7V on the sec aux rail (at least that's what I think it is cause the other two...Last edited by kotel studios; 03-17-2025, 11:54 AM.Leave a comment:
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The probable cause for no life here was an broken neutral cable going from the switch to the board.
Although before I go and power it on I must know what specs are the D24 and D16 zener's cause they had no markings and I have replaced them with 4148 signal diodes, which probably [I]could[/I] work?The probable cause for no life here was an broken neutral cable going from the switch to the board.
Although before I go and power it on I must know what specs are the D24 and D16 zener's cause they had no markings and I have replaced them with 4148 signal diodes, which probably [I]could[/I]Leave a comment:
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