Thanks Doogie. Yeah, I love the P3B-F. If we ever fix it, I'll probably recap it, because it seems like easy enough to do on that board so your info may come in handy

Hello again mate i think vrm is totaly fine . And there is problem in other component . And its more likely HW monitor 99127f or associated elements . as i research lately 39 pin of as99127f is 5vsb detect so if there is 5v not present on this pin = no start . I suggest measure r13 it should be 470 ohm also measure voltage at r13 and big resistor too . Also when you will try to start inspect if anything else getting too hot .Hopefully you get it as im not that good with english 🤣

PS . Dont try to measure pin 39 on turned on motherboard as there is high risk to touch adjacent output

Boohyaka wrote on 2022-02-27, 19:18:

Red on 1.4 to Black on GND: MM beeps, and reads 006 Black on 1.4 to Red on GND: MM beeps, and reads 007 […]
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Red on 1.4 to Black on GND: MM beeps, and reads 006
Black on 1.4 to Red on GND: MM beeps, and reads 007

Those last 2 measurements have to be done with the CPU still connected, right?

Now removed CPU, and measuring resistance between VCORE and GND (so basically I can measure again between 1.4 and GND as well?):

I'm not a Pentium III expert, but 007 or 006 in continuity mode between Vcore and GND sounds like the processor is broken (short circuit). On your meter, continuity mode is implemented as secondary function on "diode test" (other meters have it as secondary function on 200 Ohms), so the numbers are not Ohms, but millivolts that allow some milliamps to flow. Possibly a Pentium III without sufficient supply voltage applied has enough leakage for the reading to be so low, but my next step would be: Test whether you can turn on the system without the CPU installed. If it starts powering up, the problem is very likely the CPU, not the board.

ciornyi wrote on 2022-02-27, 20:23:

I suggest measure r13 it should be 470 ohm also measure voltage at r13 and big resistor too .

Hey thanks, your English is fine, but your explanations are not to me, remember you're talking with someone that if life was a RPG, would probably be level 5 at best in electronics 😁
What is r13 and how should it be measured? To ground? And what big resistor, the one I mentioned as getting too hot, bottom-left corner of the motherboard I guess?

mkarcher wrote on 2022-02-27, 20:37:

I'm not a Pentium III expert, but 007 or 006 in continuity mode between Vcore and GND sounds like the processor is broken (short circuit). On your meter, continuity mode is implemented as secondary function on "diode test" (other meters have it as secondary function on 200 Ohms), so the numbers are not Ohms, but millivolts that allow some milliamps to flow. Possibly a Pentium III without sufficient supply voltage applied has enough leakage for the reading to be so low, but my next step would be: Test whether you can turn on the system without the CPU installed. If it starts powering up, the problem is very likely the CPU, not the board.

Thanks mate, appreciate all input! But I doubt it - I have tested and will test again tomorrow (too late now, I just passed by the computer for a last check of the thread on my way to bed) and:

- Both the original Tualatin+Slotket I was originally using on the P3B-F + a spare Slot1 PIII-600 I had laying around work fine on my spare Gigabyte 6BXS
- Both don't work on the P3B-F, and I'm 99.9% sure I also tested powering it up without any CPU, and didn't work either

I'll test again tomorrow to make sure in any case and again thanks for chiming in

Just tested and confirmed @mkarcher:

- Both the original Tualatin+Slotket I was originally using on the P3B-F + a spare Slot1 PIII-600 I had laying around work fine on my spare Gigabyte 6BXS
- Both don't work on the P3B-F, and without CPU doesn't work either

Hi! Just got a P3B-F in the mail which had the exact same problem. There was a broken trace near the BIOS eeprom in my case (see photo). After fixing that trace the board was working again. The green led near the AGP slot should definitely be off until the board is fully powered on. The big resistor near the ISA slot should definitely not get warm at all, there should always be zero volts across if the board is on or off.

fool wrote on 2022-02-27, 15:54:

Shorted transistor would conduct 5V straight to Vcore or Vcore to ground. There are also other scenarios but those are the two what would possibly generate short.
I would do similar short check and measure resistance between [Vcore output <-> GND] and [Vcore output <-> 5V input].

Similar for caps. Anything in parallel on a particular segment of circuit which has failed short to ground will result in very low impedance, but you won't be able to differentiate which component has failed without further testing. You can test bipolar transistors and diodes in circuit as noted previously, but MOSFETs won't behave the same, so check the part number when testing transistors. Without fancy TDR gear and such, capacitors, resistors, and other passive components must be lifted on one side to be fully diagnosed electrically.

fool wrote on 2022-02-27, 15:54:

You can also switch multimeter to diode mode and go through those legs of both transistors, all three of them. Thats 6+6 measurements. Diode mode measures the threshold voltage what's needed for current to start flowing in the circuit. I would assume to get readings like over 0.3... to something. Zero reading would be short circuit.

As noted, this works great for bipolar junction transistors. Not so much for MOSFETs.

TheNoOne wrote on 2022-02-28, 17:42:

Hi! Just got a P3B-F in the mail which had the exact same problem. There was a broken trace near the BIOS eeprom in my case (see photo). After fixing that trace the board was working again. The green led near the AGP slot should definitely be off until the board is fully powered on. The big resistor near the ISA slot should definitely not get warm at all, there should always be zero volts across if the board is on or off.

Holy shitballs!

I'm...speechless. This went completely above my head when visually inspecting the card, probably by lack of experience. I won't have time to fix that tonight (starting a new job tomorrow 1st of March heh) but this looks very very good. Well not really, but fixable. That's probably the tiniest repair job I'll ever have done, but I should have everything necessary, experience excepted.

So these P3B-F have a common failure at that very spot? Any potential explanation about why and how to prevent it?

I'm still flabbergasted. I mean...HOW TIMELY CAN YOU BE, YOU WITCH 😁

beefy diode and thin trace, wonder what is being powered down the line and thru the via

Were you using a Voodoo 3 on this board by chance?

Not in a long time, many months, probably more than a year. I was running a FX5950 at FSB133 so AGP 89MHz. Could that be the reason? Overclocking putting too much strain?

edit: I've been running at FSB133 for years on a variety of graphic cards, but the FX5950 has been the one I used for the last few months until the issue

Spooky...

Wow! Sorry for the newbie question, now, but what would be the best way to fix this particular problem?

Just solder a small bridge with e.g. a resistor leg over the broken trace as shown here: download/file.php?id=131578&mode=view

Boohyaka wrote on 2022-02-28, 21:27:

Not in a long time, many months, probably more than a year. I was running a FX5950 at FSB133 so AGP 89MHz. Could that be the reason? Overclocking putting too much strain?

edit: I've been running at FSB133 for years on a variety of graphic cards, but the FX5950 has been the one I used for the last few months until the issue

It could well be. P2B-F/P3B-F are known for being boards that don't have great AGP voltage regulation, some of these boards can't really handle even a Voodoo 3.

appiah4 wrote on 2022-03-01, 06:03:

Boohyaka wrote on 2022-02-28, 21:27:

Not in a long time, many months, probably more than a year. I was running a FX5950 at FSB133 so AGP 89MHz. Could that be the reason? Overclocking putting too much strain?

edit: I've been running at FSB133 for years on a variety of graphic cards, but the FX5950 has been the one I used for the last few months until the issue

It could well be. P2B-F/P3B-F are known for being boards that don't have great AGP voltage regulation, some of these boards can't really handle even a Voodoo 3.

That's the first time I hear of that.

doogie wrote on 2022-03-01, 02:02:

Wow! Sorry for the newbie question, now, but what would be the best way to fix this particular problem?

Best would be tracing what is being powered by that diode and running thicker wire between two points directly.

rasz_pl wrote on 2022-03-01, 12:16:

doogie wrote on 2022-03-01, 02:02:

Wow! Sorry for the newbie question, now, but what would be the best way to fix this particular problem?

Best would be tracing what is being powered by that diode and running thicker wire between two points directly.

Yes. Use the diode through hole on the right side of the picture as a solder point. Find a through hole or good sized pad on the other side of the broken trace for the other side of the wire.

gdjacobs wrote on 2022-03-01, 21:20:

Yes. Use the diode through hole on the right side of the picture as a solder point. Find a through hole or good sized pad on the other side of the broken trace for the other side of the wire.

Right, that should work and be easy enough shouldn't it?
Would a strand of Kynar wire be too fine for the potential load? Maybe a resistor leg as suggested before would be better? I may have slightly thicker cable laying around too

further, the trace has same width behind the via. Find what is being powered.