Does anyone know which is High side and Low side?
Maybe it's easier to find this than a picture.

I looked all over for my pics but no luck so far...

My guess is higher amps P75 (75A) and then P09 (56A).

Edit: I added a pic of the area. Socket is at the top (not visible).
Yes, caps have been removed.

Nexxen wrote on 2023-08-31, 23:49:

Hello!!

I was going to solder some new MOSFETs on this motherboard but I forgot the position of these.

Maybe a schematic diagram will help:
Biostar IG31C-M7S
Look up reference designators, compare circuitry and components

P.S. Yes, P0903BDG and P75N02LDG , TO252 package

Roman555 wrote on 2023-09-02, 14:03:

Solved! And now I have the schematics too... 😀

As I was powering up the board to test the other replaced components I stumbled upon a SCD-12 @ 70-73°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … OWIE/SCD12.html

The IC that regulates power (L6703 by ST) goes to 50+°C.

I'm starting to think that the VRM IC is either busted or not working properly.

I'll solder a single P0903 and see if it blows. If it does, I'll spare the others a order either a new L6703 or just buy a new G31.
No attachment, but a very small board to test cpus.

Edit: on the schematics it appears as SS12 on that position, and to me it makes sense as the datasheet looks similar (I'm no tech so it may be my wrong assumption)
I could try to solder a SS12 instead and see what happens, if it goes up to 70°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … GHENG/SS12.html

Always more than you ask for....... 😀

EDit: 12Vcc to PD4 (highlighted)
Schottky diode; from 12.2V to 11.87V it ramps up to 70°C ----> is this normal? either failing or something else might be siphoning V somehow?

Nexxen wrote on 2023-09-02, 15:44:

Solved! And now I have the schematics too... :) […]
Show full quote

Roman555 wrote on 2023-09-02, 14:03:

Solved! And now I have the schematics too... 😀

As I was powering up the board to test the other replaced components I stumbled upon a SCD-12 @ 70-73°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … OWIE/SCD12.html

The IC that regulates power (L6703 by ST) goes to 50+°C.

I'm starting to think that the VRM IC is either busted or not working properly.

I'll solder a single P0903 and see if it blows. If it does, I'll spare the others a order either a new L6703 or just buy a new G31.
No attachment, but a very small board to test cpus.

Edit: on the schematics it appears as SS12 on that position, and to me it makes sense as the datasheet looks similar (I'm no tech so it may be my wrong assumption)
I could try to solder a SS12 instead and see what happens, if it goes up to 70°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … GHENG/SS12.html

Always more than you ask for....... 😀

EDit: 12Vcc to PD4 (highlighted)
Schottky diode; from 12.2V to 11.87V it ramps up to 70°C ----> is this normal? either failing or something else might be siphoning V somehow?

IMO, it isn't normal. What is resistance of load of PD4 (between VCC and GND pins of the chip and between the cathode and GND rail ) ? Maybe the chip or capacitors have too low resistance so current is too high for PD4

P.S. It's interesting why the mosfets were de-soldered...

Roman555 wrote on 2023-09-02, 17:53:

Nexxen wrote on 2023-09-02, 15:44:

Solved! And now I have the schematics too... :) […]
Show full quote

Roman555 wrote on 2023-09-02, 14:03:

Solved! And now I have the schematics too... 😀

As I was powering up the board to test the other replaced components I stumbled upon a SCD-12 @ 70-73°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … OWIE/SCD12.html

The IC that regulates power (L6703 by ST) goes to 50+°C.

I'm starting to think that the VRM IC is either busted or not working properly.

I'll solder a single P0903 and see if it blows. If it does, I'll spare the others a order either a new L6703 or just buy a new G31.
No attachment, but a very small board to test cpus.

Edit: on the schematics it appears as SS12 on that position, and to me it makes sense as the datasheet looks similar (I'm no tech so it may be my wrong assumption)
I could try to solder a SS12 instead and see what happens, if it goes up to 70°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … GHENG/SS12.html

Always more than you ask for....... 😀

EDit: 12Vcc to PD4 (highlighted)
Schottky diode; from 12.2V to 11.87V it ramps up to 70°C ----> is this normal? either failing or something else might be siphoning V somehow?

IMO, it isn't normal. What is resistance of load of PD4 (between VCC and GND pins of the chip and between the cathode and GND rail ) ? Maybe the chip or capacitors have too low resistance so current is too high for PD4

P.S. It's interesting why the mosfets were de-soldered...

Readings coming.

I was testing some C2D. All good. Even a E8600.
Wanted to test a few Pentium D. 1st ok, 2nd ok. 3rd, a P0903 blew. I didn't understand it was that shutting down the m/b. No short though.
Powered on again.
Another one blew (and P75 too) but I had to desolder to make the m/b work with only one rail. It was shorintg now.

I forgot to remove the Pentium D and it blew the third mosfet. My mistake. Only 1 for this power hungry cpu... Still feeling like a moron 🙁

Bought some other mosfets but they were all fakes and all died.

I ordered new ones and they are consistent in readings (Res).

Prior to all this I replaced 2 sot-23 BAT54A (but later ordered new ones) of the PD4 part.

Roman555 wrote on 2023-09-02, 17:53:

Nexxen wrote on 2023-09-02, 15:44:

Solved! And now I have the schematics too... :) […]
Show full quote

Roman555 wrote on 2023-09-02, 14:03:

Solved! And now I have the schematics too... 😀

As I was powering up the board to test the other replaced components I stumbled upon a SCD-12 @ 70-73°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … OWIE/SCD12.html

The IC that regulates power (L6703 by ST) goes to 50+°C.

I'm starting to think that the VRM IC is either busted or not working properly.

I'll solder a single P0903 and see if it blows. If it does, I'll spare the others a order either a new L6703 or just buy a new G31.
No attachment, but a very small board to test cpus.

Edit: on the schematics it appears as SS12 on that position, and to me it makes sense as the datasheet looks similar (I'm no tech so it may be my wrong assumption)
I could try to solder a SS12 instead and see what happens, if it goes up to 70°C.
https://pdf1.alldatasheet.com/datasheet-pdf/v … GHENG/SS12.html

Always more than you ask for....... 😀

EDit: 12Vcc to PD4 (highlighted)
Schottky diode; from 12.2V to 11.87V it ramps up to 70°C ----> is this normal? either failing or something else might be siphoning V somehow?

IMO, it isn't normal. What is resistance of load of PD4 (between VCC and GND pins of the chip and between the cathode and GND rail ) ? Maybe the chip or capacitors have too low resistance so current is too high for PD4

P.S. It's interesting why the mosfets were de-soldered...

anode---[SCD12]-|> --- cathode

a)
black probe on gnd and red probe on (1. anode) then (2. cathode)
(gnd-anode) 4.5K
(cathode-gnd) 35.4K

b)
anode to cathode measurements: reversing the probes so that the 30mV are in the anode and then the cathode
black com - red V =39.3K
V - com =5.7K

Desoldered SCD12 measurements:
probign one way than the other
com - V 230K
V - com 5.7K

Motherboard pads:

gnd-anode 12.3K and 50K (cathode-gnd)

anode-cathode

com-v 50K
v-com 32K

Edit: I have no SS12, SS14 could do?

Edit2: I measured a SS14 and it's 30K and 550K (one way and the other). Unless the values are so different it looks like the schottky on SCD12 is close to failing.

It was a cheap budget mainboard with weak 3-phases VRM. So it's better to use only Core CPU (not Netburst) with it.
For testing purposes I would use cheap Celeron-L or Pentium E.

I don't see any short circuits or low resistance in your measurement.
I've seen in Internet L6703 wasn't reliable. L6713 may be compatible here as someone swapped it on other mainboard models.

I don't understand resistance of the schottky. Try to set multimeter into Diode-mode.

Nexxen wrote on 2023-09-02, 15:44:

EDit: 12Vcc to PD4 (highlighted)
Schottky diode; from 12.2V to 11.87V it ramps up to 70°C ----> is this normal? either failing or something else might be siphoning V somehow?

Then 12.2-11.87=0.33V is lesser than VF=0.55V from the datasheet. It's OK

Roman555 wrote on 2023-09-02, 21:05:

It was a cheap budget mainboard with weak 3-phases VRM. So it's better to use only Core CPU (not Netburst) with it. For testing […]
Show full quote

It was a cheap budget mainboard with weak 3-phases VRM. So it's better to use only Core CPU (not Netburst) with it.
For testing purposes I would use cheap Celeron-L or Pentium E.

I don't see any short circuits or low resistance in your measurement.
I've seen in Internet L6703 wasn't reliable. L6713 may be compatible here as someone swapped it on other mainboard models.

I don't understand resistance of the schottky. Try to set multimeter into Diode-mode.

That's what I thought, a cheap C2D.
I think it just gets crazy hot around 50+°C

After resoldering the SCD12 it's stable around 58°C.
I'll buy a L6317 because the board has colours 😀

I guess these boards are doomed to fail. I'll buy some heavy duty one and be done with it.

I'll modify the resistance readings to make them intelligible.
This happens when you are not in the business (i.e. lack basic vocabulary) 🤣

If it isn't clear just point it out again.

Nexxen wrote on 2023-09-02, 21:15:

That's what I thought, a cheap C2D. I think it just gets crazy hot around 50+°C […]
Show full quote

Roman555 wrote on 2023-09-02, 21:05:

It was a cheap budget mainboard with weak 3-phases VRM. So it's better to use only Core CPU (not Netburst) with it. For testing […]
Show full quote

It was a cheap budget mainboard with weak 3-phases VRM. So it's better to use only Core CPU (not Netburst) with it.
For testing purposes I would use cheap Celeron-L or Pentium E.

I don't see any short circuits or low resistance in your measurement.
I've seen in Internet L6703 wasn't reliable. L6713 may be compatible here as someone swapped it on other mainboard models.

I don't understand resistance of the schottky. Try to set multimeter into Diode-mode.

That's what I thought, a cheap C2D.
I think it just gets crazy hot around 50+°C

After resoldering the SCD12 it's stable around 58°C.
I'll buy a L6317 because the board has colours 😀

I guess these boards are doomed to fail. I'll buy some heavy duty one and be done with it.

I'll modify the resistance readings to make them intelligible.
This happens when you are not in the business (i.e. lack basic vocabulary) 🤣

L6713. L6317 may be not existed.
Yes, this domain-specific English isn't easy for me too.
If you ask moderators to transfer the topic into a proper part of the forum it'll widen ring of readers and writers 😀
I mean General Old Hardware

By the power of Roman555, moderators, please move this to the General Old Hardware section!

Ok, let's see what happens 🤣

Yes, 6713.
If anyone could confirm that those components get that much hot I'd be glad.
As I went out for a walk I thought that I need a better board and that's it. I'll repair this one for like a SFF and some retro stuff.
I'll add a small heatsink on the L67xx chip and be sure to have a fan blowing over that zone.

Roman, thanks for your assistance so far.

Tonight I soldered a P75+P09 couple to test the board.
I tested after soldering and it didn't shut down the PSU. I went ahead and soldered the other 2 couples.
Checked and they were shorting to ground. Didn't even connect it to the PSU. Maybe it's the soldering temperature... IDK

I'm calling it as it's taking too much time and money.
Parts bin it is.

Nexxen wrote on 2023-09-18, 01:47:

Tonight I soldered a P75+P09 couple to test the board. I tested after soldering and it didn't shut down the PSU. I went ahead a […]
Show full quote

Tonight I soldered a P75+P09 couple to test the board.
I tested after soldering and it didn't shut down the PSU. I went ahead and soldered the other 2 couples.
Checked and they were shorting to ground. Didn't even connect it to the PSU. Maybe it's the soldering temperature... IDK

I'm calling it as it's taking too much time and money.
Parts bin it is.

Maybe there is some electricity charge in wires of a MOSFET so the MOSFET is opened. Try to measure later when the charge leaks.
Once I observed strange measurement in a VRM but when I de-soldered MOSFET it behaved totally right (no shorts, opened/closed) .

Roman555 wrote on 2023-09-19, 15:55:

Nexxen wrote on 2023-09-18, 01:47:

Tonight I soldered a P75+P09 couple to test the board. I tested after soldering and it didn't shut down the PSU. I went ahead a […]
Show full quote

Tonight I soldered a P75+P09 couple to test the board.
I tested after soldering and it didn't shut down the PSU. I went ahead and soldered the other 2 couples.
Checked and they were shorting to ground. Didn't even connect it to the PSU. Maybe it's the soldering temperature... IDK

I'm calling it as it's taking too much time and money.
Parts bin it is.

Maybe there is some electricity charge in wires of a MOSFET so the MOSFET is opened. Try to measure later when the charge leaks.
Once I observed strange measurement in a VRM but when I de-soldered MOSFET it behaved totally right (no shorts, opened/closed) .

Didn't know that, I'll check later.
Btw, I was going through some dead bards and found a L6713. I'll replace the old 6703.

I replaced the L6703 replaced with a L6713.
From 70°C to 32°C. Probably it was dead and killing all the power mosfets...

I'll solder stuff tonight and report.

Btw, yoy were right, some p09 and p75 were only hot and with residual charge.
I measured and no shorts...

Ok, it POSTs.
Now, I have to resolder a few caps and it should be ok.

No more Pentium D test with this board.

Edit: OK 100%

Roman555, big thank you for your help!!

Nexxen wrote on 2023-10-13, 23:55:

Ok, it POSTs. Now, I have to resolder a few caps and it should be ok. […]
Show full quote

Ok, it POSTs.
Now, I have to resolder a few caps and it should be ok.

No more Pentium D test with this board.

Edit: OK 100%

Roman555, big thank you for your help!!

It was nothing, I'm glad you managed to fix it

Roman555 wrote on 2023-10-16, 19:22:

Nexxen wrote on 2023-10-13, 23:55:

Ok, it POSTs. Now, I have to resolder a few caps and it should be ok. […]
Show full quote

Ok, it POSTs.
Now, I have to resolder a few caps and it should be ok.

No more Pentium D test with this board.

Edit: OK 100%

Roman555, big thank you for your help!!

It was nothing, I'm glad you managed to fix it

Well, I would have never thought to look for a compatible component.
It was that. Credit when deserved 😉

I got some XPs and close to level up 🤣