Broken Pentium 2 Motherboard

[lti]

Re: Broken Pentium 2 Motherboard

Asus used Rubycon YXG a lot (along with I.Q) back then. Nichicon HE will probably be fine.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Well I recapped and the issue remains. What else could be causing this?

[momaka]

Re: Broken Pentium 2 Motherboard

What power supply are you using to test the board with? (brand, model, and most preferably - internal pictures of the PSU, would be great)

I would suggest you visually inspect the board for any damage that may have been done by the previous power supply. First clean the dust from it, then look for any burn marks or darkened areas on the PCB. Also, if any of the chips has a crack on it or is missing pieces, it may be bad.

Probably a good idea to also run through all of the standard motherboard troubleshooting steps. That is:
- Disconnect everything not from the motherboard that's not necessary. Have only the CPU, RAM (1 module is enough), and graphics card plugged in (along with the PSU, of course).
- Remove CMOS battery or set jumper on the board (if it has one) to CLEAR CMOS settings.
- Re-seat CPU and graphics card.
- Apply power and test when above steps are completed and note results.

I think the SB may be gone. But I wouldn't ditch the motherboard just yet without first checking all of the voltage regulators on it. Equally good chance that only a small regulator or MOSFET shorted somewhere and is preventing the motherboard from booting. If the above steps don't yield any results (and please post what results you get), you will need to provide good high-quality pictures of your board (with a proper camera, not a cell phone) and a multimeter if you want to further troubleshoot the motherboard.

But anyways, run through the standard steps first just to see what results you get. Also, you say you can still turn the motherboard ON and OFF with the switch. In that case, after you turn it OFF, try turning it ON with the switch again. If the computer has a RESET switch, try resetting the PC after you turn on the motherboard. Note any changes in the behavior of the motherboard. Post what results you get.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

What power supply are you using to test the board with? (brand, model, and most preferably - internal pictures of the PSU, would be great)

I would suggest you visually inspect the board for any damage that may have been done by the previous power supply. First clean the dust from it, then look for any burn marks or darkened areas on the PCB. Also, if any of the chips has a crack on it or is missing pieces, it may be bad.

Probably a good idea to also run through all of the standard motherboard troubleshooting steps. That is:
- Disconnect everything not from the motherboard that's not necessary. Have only the CPU, RAM (1 module is enough), and graphics card plugged in (along with the PSU, of course).
- Remove CMOS battery or set jumper on the board (if it has one) to CLEAR CMOS settings.
- Re-seat CPU and graphics card.
- Apply power and test when above steps are completed and note results.

I think the SB may be gone. But I wouldn't ditch the motherboard just yet without first checking all of the voltage regulators on it. Equally good chance that only a small regulator or MOSFET shorted somewhere and is preventing the motherboard from booting. If the above steps don't yield any results (and please post what results you get), you will need to provide good high-quality pictures of your board (with a proper camera, not a cell phone) and a multimeter if you want to further troubleshoot the motherboard.

But anyways, run through the standard steps first just to see what results you get. Also, you say you can still turn the motherboard ON and OFF with the switch. In that case, after you turn it OFF, try turning it ON with the switch again. If the computer has a RESET switch, try resetting the PC after you turn on the motherboard. Note any changes in the behavior of the motherboard. Post what results you get.

The power supply I am using is out of my main pc but I got a new one because the fan it it was going. It works fine for diagnostics because I don't need to have it running for long. The power supply is a FSP Group Inc. Model FSP350-60PN.

No chips or anything on the board look visually bad.

I went through all of the standard troubleshooting steps and the results were all the same.

I have a multimeter and the reset switch does nothing when pressed while the board is active.

I will attach the pictures of the motherboard and power supply.

[momaka]

Re: Broken Pentium 2 Motherboard

The pictures are a little bit low quality, but I'll proceed anyways.
...
I attached two pictures.
On the first one, the red dots indicate the DC voltage you should measure. Measure each voltage with respect to ground (i.e. have the black multimeter probe connected to a black wire on the power supply or touching a metal part of the PC case). For transistor #5, measure only the side with the single pin, not the side that has the 3 pins. To measure the voltage, you need to have the motherboard turned ON. Be careful not to short anything with your multimeter leads.

On the second picture, the green diodes indicate the diodes to test. Use your multimeter's diode test function. Do this with the board powered OFF and DISCONNECTED from the power supply and all peripherals. The red dots indicate the voltages to measure. Post your results here.

If you're not sure how to use your multimeter, check the video below and feel free to ask any questions here.
video:
http://www.youtube.com/watch?v=bF3OyQ3HwfU

[Th3_uN1Qu3]

Re: Broken Pentium 2 Motherboard

I've seen that CWT PSU before... Matter of fact i think i have two boards of that tossed somewhere.

The good: Can't kill it. UC3842-based main PSU, undersized MOSFET and ridiculously tiny heatsinks, but the current limit is set low enough that it just won't die no matter what you try.

The bad: "Suicidal" 5vsb circuit as mentioned above... One of mine supplied 15 volts on the 5vsb. Vented the caps, of course, but even then, it just kept going. Tried my best to damage it by high load, shorts, you name it... didn't die. Stripped it for parts, which i think is the best way to go with one of those PSUs. CWT should be ashamed for making such a lousy and dangerous power supply.

Bottom line: I think that mobo is toast. Feel free to try and revive it tho...

[canadaboy25]

Re: Broken Pentium 2 Motherboard

I've seen that CWT PSU before... Matter of fact i think i have two boards of that tossed somewhere.

The good: Can't kill it. UC3842-based main PSU, undersized MOSFET and ridiculously tiny heatsinks, but the current limit is set low enough that it just won't die no matter what you try.

The bad: "Suicidal" 5vsb circuit as mentioned above... One of mine supplied 15 volts on the 5vsb. Vented the caps, of course, but even then, it just kept going. Tried my best to damage it by high load, shorts, you name it... didn't die. Stripped it for parts, which i think is the best way to go with one of those PSUs. CWT should be ashamed for making such a lousy and dangerous power supply.

Bottom line: I think that mobo is toast. Feel free to try and revive it tho...

Wow, I'm really glad I took that out of my main pc lol.

This was not the power supply that took out my mobo.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

The pictures are a little bit low quality, but I'll proceed anyways.
...
I attached two pictures.
On the first one, the red dots indicate the DC voltage you should measure. Measure each voltage with respect to ground (i.e. have the black multimeter probe connected to a black wire on the power supply or touching a metal part of the PC case). For transistor #5, measure only the side with the single pin, not the side that has the 3 pins. To measure the voltage, you need to have the motherboard turned ON. Be careful not to short anything with your multimeter leads.

On the second picture, the green diodes indicate the diodes to test. Use your multimeter's diode test function. Do this with the board powered OFF and DISCONNECTED from the power supply and all peripherals. The red dots indicate the voltages to measure. Post your results here.

If you're not sure how to use your multimeter, check the video below and feel free to ask any questions here.
video:
http://www.youtube.com/watch?v=bF3OyQ3HwfU

Sorry about the low quality pics. I dropped my camera so it don't focus good anymore.

I will list the voltages - these were read with only power, cpu, and ram installed
1 - 2.876
2 - 2.12
3 - 0.863
4 - 0.585
5 - 5.033
6 - 0.009

I numbered the diodes on the attached picture.
Diode 1,2,4,5, and 6 tested good. The diode labeled 3 is that 3 leaded black thing I am guessing, if so how do I test it?
Diode number 7 gave me a voltage drop of 0.6 both ways like any other diode being tested forward-biased. Is this a bad diode or does it read both ways because it is in-circut?

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Was I supposed to have graphics cards and power led's installed for the voltages tests?

[momaka]

Re: Broken Pentium 2 Motherboard

If the motherboard doesn't have on-board one, then yes, you need the graphics card. LEDs: optional... but it never huts to have them.

I was about to say, some of the voltages do seem kind of low, as if when a certain hardware isn't installed or powering on and the system is in halt on some low power state.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

The voltages were all the same as before with led's graphics card, and sound card installed.

[momaka]

Re: Broken Pentium 2 Motherboard

Oh woops. Just forgot to say...
When you are measuring the voltages for items 1 through 6, you need to measure the voltage at each red dot with respect to ground (i.e. PC case), not with respect to each other. Therefore, there should be two voltages for each item in 1 through 6 (i.e. #1: voltage-A, voltage-B; #2 voltage-A, voltage-B... etc.). Make the first voltage the one where the dot is on the tab (the side on the MOSFET that has only a single pin).

The diode labeled 3 is that 3 leaded black thing I am guessing, if so how do I test it?

That's most likely a BJT transistor or a MOSFET and not a diode. But just check to see if there is a short circuit (0.00 Ohms or close) between any of its pins. If yes, let me know. Otherwise, it's probably not bad.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

The tabs on the MOSFET's have continuity with the negative leads on my power supply... So that means that there is only one voltage doesn't it?

The little black thing is not shorted.

[momaka]

Re: Broken Pentium 2 Motherboard

The tabs on the MOSFET's have continuity with the negative leads on my power supply... So that means that there is only one voltage doesn't it?

Not necessarily.
If you did those continuity measurements with the power supply connected to the motherboard, that could be the reason why. MOSFETs usually aren't connected like that, unless this is some weird design I haven't seen before (but I doubt ASUS did that here).
Try measuring the voltages anyways. If you get zero volts at the tabs, then you are correct. But again, it doesn't make much sense to me to have the MOSFETs connected like that. Just about every motherboard I've seen uses N-channel FETs, where the tab is always the Drain and the right leg (as viewed from top with legs pointing down) is Source.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Not necessarily.
If you did those continuity measurements with the power supply connected to the motherboard, that could be the reason why. MOSFETs usually aren't connected like that, unless this is some weird design I haven't seen before (but I doubt ASUS did that here).
Try measuring the voltages anyways. If you get zero volts at the tabs, then you are correct. But again, it doesn't make much sense to me to have the MOSFETs connected like that. Just about every motherboard I've seen uses N-channel FETs, where the tab is always the Drain and the right leg (as viewed from top with legs pointing down) is Source.

Real sorry I don't know where those voltages came from.

I have attached the good ones.

And you were right there is no continuity to ground.

[momaka]

Re: Broken Pentium 2 Motherboard

No problem, it's all good .

The voltage readings on transistor 6 look bad. Such large devices are normally used to regulate voltages to chipsets, RAM, and other more power-hungry circuits. The fact that you have 0V for both A and B is weird.

I would say, check the voltage on transistor 6 again, and if you still get 0V, turn OFF power, disconnect power supply, and measure resistance between pins A and B using lowest resistance scale of your multimter (usually 200 Ohms on manual multimters... if you have an automatic multimeter, don't worry - just take note of the units). Also measure resistance between A and ground and B and ground. Let me know what you get.

While you're at it, can you also tell me the part number of transistor 6. It should be writte on top of it. Motherboard also has a label near the tab. I'm seeing "1802I" or something similar. Can you confirm?

The rest looks more or less good.
MOSFETs 1 and 2 form a synchronous buck converter for the CPU VRM. 2.8V is normal if you're running a Klamath core Pentium II (common for the 233-300 MHz Pentium IIs).

MOSFETs 3 and 4 seem to be arranged in some kind of linear VRM circuit. I'm guessing the output of MOSFET 4 (the second voltage), ~3.3V, is for the RAM and possibly CPU cache. At 3.5V, it seems to be a bit above the 5% tolerance, but it could be normal since the motherboard is not booting and whatever circuit is supposed to use that voltage rail isn't due to being disabled or on stand-by.

Transistor 5 may be just a simple pass-through. Can you check the voltage on its other pins? I just want to see what it does. Be careful not to slip your multimeter leads and short its pins (very easy to do and I've done it too - though I got lucky and didn't damange anything fortunately).

[canadaboy25]

Re: Broken Pentium 2 Motherboard

wow I attached that file from my linux laptop... came out horribly

sorry that the numbers were all in a line like that

Will check on those things tomorrow thanks

re-attached the file so others will be able to read it better (or u )

[goontron]

Re: Broken Pentium 2 Motherboard

what do you mean in a line? they look pretty darn organised to me.

[momaka]

Re: Broken Pentium 2 Motherboard

what do you mean in a line? they look pretty darn organised to me.

In Linux, yes. But Notepad was throwing a hissy-fit. Wordpad worked just fine though, so no problem .
And of course, there's always the mighty Word .

[canadaboy25]

Re: Broken Pentium 2 Motherboard

I would say, check the voltage on transistor 6 again, and if you still get 0V, turn OFF power, disconnect power supply, and measure resistance between pins A and B using lowest resistance scale of your multimter (usually 200 Ohms on manual multimters... if you have an automatic multimeter, don't worry - just take note of the units). Also measure resistance between A and ground and B and ground. Let me know what you get.

The voltages were still the same.

Between the pins I get 376 000 ohms.
Between pin A (tab) and ground I get 377 000 ohms.
Between pin B (right pin on MOSFET) and ground I get 0.2 ohms.

While you're at it, can you also tell me the part number of transistor 6. It should be writte on top of it. Motherboard also has a label near the tab. I'm seeing "1802I" or something similar. Can you confirm?

D1802: I believe that those are the markings on the MOSFET
T 7J

The numbers on the motherboard are 1802T (You were close )

Transistor 5 may be just a simple pass-through. Can you check the voltage on its other pins? I just want to see what it does. Be careful not to slip your multimeter leads and short its pins (very easy to do and I've done it too - though I got lucky and didn't damange anything fortunately).

1 - 2.166
2 - 5.012
3 - 1.512

I have attached a picture with the numbered pins so it is easier to read


I had the ram, cpu, graphics card, and audio card in for all of these tests.