Broken Pentium 2 Motherboard

[canadaboy25]

Hello, I have an old Pentium 2 motherboard that I think is fried.

I had just brought it out of storage (my first pc ) and booted it up and it worked! I tried uninstalling a stupid program but the pc crashed while doing so and the hard drive got corrupted. I was upset so I just went to bed. The next morning I came down to find that the computer would not turn on. I pulled out my psu tester and the power supply was shot. I took a spare power supply, tested it (worked fine) and plugged it in. This psu had no white (-5v) wire but the old one did. I plugged the psu in and the instant I turned the switch on (psu switch) the fans turned on and the hard drive spinned up. The power button did nothing and there was nothing on the screen. I tried it with a psu that had a white wire but same thing. At that time I opened up the fried psu and there was severe meltage. I didn't know what to think. I pulled all of the ram out and tried, it powered on the second i plugged it in and there were no beep codes. I have tested all of the ram in a different pc and it tested fine. The graphics card is a pci one not accelerated graphics. I tried an accelerated graphics card in it but same thing. The old graphics card did nothing in a newer computer and gave error messages in an older one. The processor warms up when power is applied so I don't know what is wrong. i tested the power button and it wasn't stuck.

The board number is P2L97 REV. 105 if that helps.

I would really like to see what is wrong with this thing and if it is fixable.

Thanks and please tell me if you need more information.

canadaboy25

[momaka]

Re: Broken Pentium 2 Motherboard

Brand and internal pictures of the old power supply that had a "meltdown" would help. If this is one of those cheap gutless wonder PSUs with a suicide 5VSB circuit (i.e. the infamous 2-transistor circuit that made the Bestec ATX-250-12E become known as a "motherboard killer"), then chances are the Southbridge is gone. But it could also be bad caps too.

When you plug in a working power supply, does the Southbridge get very hot very quickly? If yes, then SB is gone. If not, post what brand of capacitors the motherboard has. Google images of the board shows "X" type vents and not Nichicon, so I'm guessing it's nothing good. Probably I.Q., OST, or some other garbage.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Brand and internal pictures of the old power supply that had a "meltdown" would help. If this is one of those cheap gutless wonder PSUs with a suicide 5VSB circuit (i.e. the infamous 2-transistor circuit that made the Bestec ATX-250-12E become known as a "motherboard killer"), then chances are the Southbridge is gone. But it could also be bad caps too.

When you plug in a working power supply, does the Southbridge get very hot very quickly? If yes, then SB is gone. If not, post what brand of capacitors the motherboard has. Google images of the board shows "X" type vents and not Nichicon, so I'm guessing it's nothing good. Probably I.Q., OST, or some other garbage.

Hi, thanks for the quick reply.

I'm real sorry the psu that had the meltdown was on a different one. The fan was liquified and the metal melted there was fan all over the computer box lol.

The bad psu that was on this one had a burn mark on the board. It was a Sunny Technologies Co.,LTD. MODEL: CWT ATX-250ATX. I noticed it had bad caps so I did a quick re-cap just to see if it would work so that is why there are some new caps.

I'm a total noob to motherboard repair so um... could you appoint me to the southbridge.... lol

canadaboy25

[goontron]

Re: Broken Pentium 2 Motherboard

Brand and internal pictures of the old power supply that had a "meltdown" would help. If this is one of those cheap gutless wonder PSUs with a suicide 5VSB circuit (i.e. the infamous 2-transistor circuit that made the Bestec ATX-250-12E become known as a "motherboard killer"), then chances are the Southbridge is gone. But it could also be bad caps too.

yep, that's the one!

[canadaboy25]

Re: Broken Pentium 2 Motherboard

yep, that's the one!

Oh my....

What do I do now?

canadaboy25

[canadaboy25]

Re: Broken Pentium 2 Motherboard

What brand of capacitors does the motherboard have. Google images of the board shows "X" type vents and not Nichicon, so I'm guessing it's nothing good. Probably I.Q., OST, or some other garbage.

It says I.Q. on the caps.

canadboy25

[momaka]

Re: Broken Pentium 2 Motherboard

If your board looks like this:
http://ecx.images-amazon.com/images/...L._SL1500_.jpg
The Southbridge is the square black chip right by the PCI slots where it says "P2L97". If this chip gets very hot when a working PSU is plugged in the computer, then the motherboard is gone.
If the chip doesn't get very hot, see if the motherboard responds to a "turn-off" signal - i.e. holding the power button down to turn OFF the motherboard after it has been turned ON. This is one of the very basic functions of the SB. If this function doesn't work, SB is likely done for. (make sure you have RAM for this test, though.)

25The bad psu that was on this one had a burn mark on the board. It was a Sunny Technologies Co.,LTD. MODEL: CWT ATX-250ATX.

Okay, do NOT use this power supply on ANY computer right now. That power supply has the same suicide 2-transistor 5VSB circuit I mentioned, and the burn mark is exactly because of that.

If you have a multimeter, though, plug the PSU in the wall (but do NOT connect to a computer) and measure voltage on the 5VSB wire on the main 20 pin connector (normally, this would be the purple wire... so measure between purple wire and any black wire). You should get about 5V (and plus/minus 0.25V max). Try to do this quickly and don't keep the PSU plugged in for too long.

As far as the I.Q. caps - those aren't very good. Because of that, there's a chance this problem may be a bad caps issue too. If that's the case, then all you would need to do is recap the motherboard (particularly the caps around the CPU) and it may work like new again.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Hey, I left the board plugged in for over 10mins and the southbridge was only warm. The board does turn off when i hold the power button!

If I were to recapp the board the caps are 1000uf 6.3v. Could i recap with 10 or 16v caps? I thought this was true but i wanted to make sure.

canadaboy25

[momaka]

Re: Broken Pentium 2 Motherboard

Yes, both 10V and 16V caps would work, but if you use properly-rated low-ESR caps, there isn't really any benefit from that. The caps, however, do need to be low-ESR, and preferably something that matches what you have right now (more on that in the next paragraph) or something better. I recommend getting them either from badcaps.net store, Digikey, or Mouser. Avoid eBay at all costs - way too many fakes there. There's only one guy that doesn't sell fakes, but his name escapes me now. Also avoid local shops and Radio Shack - they more than likely have nothing that is suitable.

As far as the I.Q. caps, do they have a series name (usually 2 or 3 letter code)? Also, check their dimensions (most importantly, the diameter). From the picture, the ones around the CPU seem like either 8 mm or 10 mm diameter. This matters because the lead spacing between 8 mm and 10 mm is slightly different. Not that one won't work with the other, but you'd have to bend leads. And fitting 10 mm caps in 8 mm spots isn't always possible. Since this is a Pentium 2 motherboard, the caps don't have to be ultra-low ESR. Most likely Panasonic FR and FM, Nichicon HD, Chemicon KZE, and Rubicon ZL and ZLG and ZLH and ZLJ will work just fine. Higher grade caps like Panasonic FJ and FL, Nichicon HM and HN and HZ, and Rubycon MBZ and MCZ should be fine too.

I'm willing to say even Nichicon HE and United Chemicon KY would work, but I'd rather check what series those I.Q. caps are first before assuming too much.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

I have 10 10v and 10 16v caps. I bought a kit from digikey or mouser and they have always worked for me. They are the same size lead spacing. I need 18 caps so would it be ok to use some 10v and some 16v?

I have an esr tester and tested one cap I took off and it tested about 928. So that means good cause it should be within 10% so why would I be recapping?

Would a power surge from a psu cause bad caps?

The caps say nothing on them besides the uf, voltage, and temp rating.

canadaboy25

[lti]

Re: Broken Pentium 2 Motherboard

I.Q caps never have a series marking. There are some with silver printing that are probably general purpose and some with copper-colored printing that have varying ESR ratings. The newer ones are close to Nichicon HM, but caps with identical markings have existed before anyone could make such low ESR caps.

I don't think the caps would cause that problem.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

I don't think the caps would cause that problem.

Well then what do you think the problem could be?

It isn't the southbridge and not the caps.

What would a power surge fry?

[momaka]

Re: Broken Pentium 2 Motherboard

I have an esr tester and tested one cap I took off and it tested about 928. So that means good cause it should be within 10% so why would I be recapping?

For motherboards, the ESR of the caps is just as important as the capacitance. You can have a cap that shows normal capacitance but still have high ESR and cause the motherboard to act all weird.

That's where the ESR meter comes in handy - with it you can test if a particular cap is bad. However, you'd have to pull every single cap and measure it, because on the board, most of the capacitors around the CPU are in parallel and so cannot be accurately measured by the ESR meter. The ESR meter will read the overall ESR, which will appear quite low. But this combined low ESR may not actually be enough to make the circuit work.
That's why ESR is that important.

Also, what brand and series of capacitors did you get from Mouser/Digikey? Again, ESR is very important. If you have general purpose caps, (or worse, 85C rated caps), then you can't use this on the motherboard or in a PSU.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

For motherboards, the ESR of the caps is just as important as the capacitance. You can have a cap that shows normal capacitance but still have high ESR and cause the motherboard to act all weird.

That's where the ESR meter comes in handy - with it you can test if a particular cap is bad. However, you'd have to pull every single cap and measure it, because on the board, most of the capacitors around the CPU are in parallel and so cannot be accurately measured by the ESR meter. The ESR meter will read the overall ESR, which will appear quite low. But this combined low ESR may not actually be enough to make the circuit work.
That's why ESR is that important.

Also, what brand and series of capacitors did you get from Mouser/Digikey? Again, ESR is very important. If you have general purpose caps, (or worse, 85C rated caps), then you can't use this on the motherboard or in a PSU.

I have a XC6013L tester that i use to test caps. I took the caps off of the board when I tested them. Is this meter testing capacitance or esr? I didn't know there was a difference?. As I said before the old capacitors said nothing about the series on them so how would I go about picking the type of new cap to put in?

I am hoping the caps I have here are good enough to find the problem because if it turns out to be the caps then I will go buy highquality ones. These I was hoping would be good enough to troubleshoot.

The caps are Chong brand CD11X -40 to +105°C.

I know that microfarads are the capcitance but is the esr invisible to my meter?

[momaka]

Re: Broken Pentium 2 Motherboard

I'm not familiar with that meter but searches on Google suggests the XC6013L can only measure capacitance.

ESR and ripple current (the other two important parameters besides the voltage and capacitance) are only given in the capacitor's data sheet (Google Nichicon HM, for example).
With an ESR meter, you can actually measure the ESR of capacitors. However, when it comes to very low ESR capacitors (such as on motherboards), an ESR meter may only be able to tell you if a capacitor is bad (has high ESR) or not.

Basically, ESR measures the internal resistance of the capacitor. The higher that resistance, the longer it takes to charge and discharge the capacitor. High ESR is almost always undesirable. And when capacitors go bad or get old, their ESR goes up (usually much faster for the crappy Chinese/Taiwanese brands than high quality Japanese ones).

I'm almost certain those Chong capacitors are not low ESR (or at least not low enough for motherboard repair). Moreover, they sound like the run-of-the-mill cheap Chinese capacitors (usually recognizable by the "CD***" series/date code/whatever it symbolizes). I wouldn't use them for ANY repair, because cheap capacitors like that don't last long at all. Maybe only for testing circuits on a breadboard.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

I'm not familiar with that meter but searches on Google suggests the XC6013L can only measure capacitance.

ESR and ripple current (the other two important parameters besides the voltage and capacitance) are only given in the capacitor's data sheet (Google Nichicon HM, for example).
With an ESR meter, you can actually measure the ESR of capacitors. However, when it comes to very low ESR capacitors (such as on motherboards), an ESR meter may only be able to tell you if a capacitor is bad (has high ESR) or not.

Basically, ESR measures the internal resistance of the capacitor. The higher that resistance, the longer it takes to charge and discharge the capacitor. High ESR is almost always undesirable. And when capacitors go bad or get old, their ESR goes up (usually much faster for the crappy Chinese/Taiwanese brands than high quality Japanese ones).

I'm almost certain those Chong capacitors are not low ESR (or at least not low enough for motherboard repair). Moreover, they sound like the run-of-the-mill cheap Chinese capacitors (usually recognizable by the "CD***" series/date code/whatever it symbolizes). I wouldn't use them for ANY repair, because cheap capacitors like that don't last long at all. Maybe only for testing circuits on a breadboard.

So basically I need an ESR tester. Could you recommend one?

[momaka]

Re: Broken Pentium 2 Motherboard

ESR meters is not my area of expertise (in terms of which one to get), but I can name you several popular ones:
- AnaTek Blue ESR meter
- ESR Micro (both version 3.1 and 4 are good)
- Peak Atlas ESR meter
These aren't exactly cheap devices, but if you're going to do a lot of repairs that involve electronics with capacitors, then it's definitely worth getting one.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Hey I will look into one of those. I currently have a long list of stuff I need from mouser. Would these caps be low ESR? --> http://ca.mouser.com/ProductDetail/N...MjJTwEpwhzI%3d

They are very cheap so I could buy them along with my other stuff and recap the whole board and be done with the possibility of bad caps. (Hopefully will be fixed)

Do you think that this will be the best plan or should I find different caps?

[momaka]

Re: Broken Pentium 2 Motherboard

Those are Nichicon HE, which are low ESR caps. Generally, their ESR is not low enough for motherboard use (at least not for anything Pentium 3 and newer), but they may be just good enough for your board.
You can get Nichicon HM for cheaper, though:
http://ca.mouser.com/ProductDetail/N...AzGLFwTEDUA%3d
And Nichicon HM are motherboard-grade capacitors, so you'd have no problem using those.

However, if you ever plan or recapping any power supplies, then Nichicon HE would be a better choice since their ESR is low but not too low. Nichicon HM, HN, HZ, and other capacitors in their grade are generally unsuitable for power supply use.

[canadaboy25]

Re: Broken Pentium 2 Motherboard

Those are Nichicon HE, which are low ESR caps. Generally, their ESR is not low enough for motherboard use (at least not for anything Pentium 3 and newer), but they may be just good enough for your board.
You can get Nichicon HM for cheaper, though:
http://ca.mouser.com/ProductDetail/N...AzGLFwTEDUA%3d
And Nichicon HM are motherboard-grade capacitors, so you'd have no problem using those.

However, if you ever plan or recapping any power supplies, then Nichicon HE would be a better choice since their ESR is low but not too low. Nichicon HM, HN, HZ, and other capacitors in their grade are generally unsuitable for power supply use.

Thanks for all of the info on the caps.

I will order them and post back when it is recapped.