Busted Pentium 2 Power Supply?

[canadaboy25]

Hello I have an old pc with a pentium 2 processor and the power supply went on it.

I tried a newer working one but all it did was start the fans Instantly when i plugged it in. The hard drive and disk drive spin up and the processor gets hot. There is no video output either.

I also noticed that the new ps had no -5 volt wire on it. I swapped the ps out with a slightly older one that had a -5 volt wire, still same thing. The side of this power supply said supports intel Pentium 4 and Supports AMD Athon.

Do I need an older power supply or did my mb get fried?

canadaboy25

[LDSisHere]

Re: Busted Pentium 2 Power Supply?

What brand/model of motherboard is this? At one point Dell was using an ATX connector with a non-standard pin out, I am not sure if any other manufacturers did the same.

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

What brand/model of motherboard is this? At one point Dell was using an ATX connector with a non-standard pin out, I am not sure if any other manufacturers did the same.

It doesnt show a make but there is a number P2L97

canadaboy25

[larrymoencurly]

Re: Busted Pentium 2 Power Supply?

Here's a couple of diagrams of nonstandard Dell power supply motherboard connectors and industry standard ATX connectors. Notice that nonstandard Dell PSUs have blue-white wires for the +3.3V, not the usual orange wires, and on those nonstandard Dell PSUs the orange wire is for Power_Good status. I don't know when Dell switched to industry standard ATX PSUs, but their Optiplex GX260 uses standard PSUs, and it goes back to around 2002-2003 (Pentium 4, separate 4-pin 12V plug for CPU power, no SATA ports)

[LDSisHere]

Re: Busted Pentium 2 Power Supply?

If the attached PDF matches your motherboard it looks like it uses a standard (older) ATX connector / power. Your motherboard may have been damaged when the original power supply went bad. Some good quality pictures of the board would help in the troubleshooting if you want to try to get it working again.

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

Here's a couple of diagrams of nonstandard Dell power supply motherboard connectors and industry standard ATX connectors. Notice that nonstandard Dell PSUs have blue-white wires for the +3.3V, not the usual orange wires, and on those nonstandard Dell PSUs the orange wire is for Power_Good status. I don't know when Dell switched to industry standard ATX PSUs, but their Optiplex GX260 uses standard PSUs, and it goes back to around 2002-2003 (Pentium 4, separate 4-pin 12V plug for CPU power, no SATA ports)

All of the wire colors matched on both ps's I tried so I don't know.

Why does the power supply say supports Intel Pentium 4 and supports AMD Athlon?

How can a power supply not suppport a processor?

canadaboy25

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

The power supply I was using that broke was from Sunny Technologies Co., LTD. MODEL: CWT ATX-250ATX

If that helps any.

Is there a way we could fix the power supply? I have fixed others on the past.

The broken power supply had bad caps and a very dark portion of board around one. The fuse was still good.

canadaboy25

[pfrcom]

Re: Busted Pentium 2 Power Supply?

there is a number P2L97

Which is an Asus board, dating from the time Asus was a reliable brand

@OP - are you sure you had both power feeds plugged into the motherboard, particularly the small square one with four connectors in it ?

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

If the attached PDF matches your motherboard it looks like it uses a standard (older) ATX connector / power. Your motherboard may have been damaged when the original power supply went bad. Some good quality pictures of the board would help in the troubleshooting if you want to try to get it working again.

My board is a little different than the one described it also says Rev. 1.05 on the MB.

Here are some pics sorry if their not good enough I can retake.

canadaboy25

[LDSisHere]

Re: Busted Pentium 2 Power Supply?

All of the wire colors matched on both ps's I tried so I don't know.

Why does the power supply say supports Intel Pentium 4 and supports AMD Athlon?

How can a power supply not suppport a processor?

canadaboy25

On P4 boards and AMD equivalents there is an additional 4 pin 12V power connector to power the processor in addition to the ATX one. Some newer boards have an 8 pin connector for the processor.

If you have not already done so, disconnect the power switch from the motherboard then connect up the power supply with the -5V. See if it still powers on when you connect the power supply, as this will rule out the switch being stuck. If it does attempt to power on listen for any beeps. (Obviously have all the important bits connected when doing this.) Is the video card on board and if so do you have a pci one you could try? The CMOS settings may have been reset and it could be defaulting to auto power on after a power failure if it has that option.

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

On P4 boards and AMD equivalents there is an additional 4 pin 12V power connector to power the processor in addition to the ATX one. Some newer boards have an 8 pin connector for the processor.

If you have not already done so, disconnect the power switch from the motherboard then connect up the power supply with the -5V. See if it still powers on when you connect the power supply, as this will rule out the switch being stuck. If it does attempt to power on listen for any beeps. (Obviously have all the important bits connected when doing this.) Is the video card on board and if so do you have a pci one you could try? The CMOS settings may have been reset and it could be defaulting to auto power on after a power failure if it has that option.

My AMD Athlon PC doesn't even use the 4 pin processor connector but that power supply doesnt work on the broken board. When i plug the power supply in the second i turn it on the computer starts spinning the fans, hard drive, cd, and the processor warms up. There are no beeps or anything on the screen.

When I put the card in a vintage pentium-s machine it gives a beep error sohould I try it in the AMD Athlon PC?

My button is not stuck I have confirmed that with a digital multimeter on continuity test.

canadaboy25

[ratdude747]

Re: Busted Pentium 2 Power Supply?

The power supply I was using that broke was from Sunny Technologies Co., LTD. MODEL: CWT ATX-250ATX

If that helps any.

Is there a way we could fix the power supply? I have fixed others on the past.

The broken power supply had bad caps and a very dark portion of board around one. The fuse was still good.

canadaboy25

Probably had bad caps, CWT made PSUs were/are known for that issue.

They are also known for a 5vsb (5 volt standby issue) defect that will cause the nominally 5V stand-by rail to increase in voltages high enough to fry motherboards. While usually associated with older antec PSUs, made by CWT, I could see other CWT PSUs with the same issue. It's due to the circuit design, which when a certain cap fails (the "killer cap"), the voltage control goes wacky. FWIW, bestec also used this design in some of their 250W and 300W units and had similar issues with it (and a similar reputation for fried motherboards)

If you have a multimeter, power the PSU, unconnected to a mainboard, and measure between the purple wire at the ATX plug (5vsb) and any black wire (ground). If it's anything significantly over 5V, then you have a motherboard killer needing a recap and (probably) a fried PII board... and unless and until it's recapped, don't use it...

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

Probably had bad caps, CWT made PSUs were/are known for that issue.

They are also known for a 5vsb (5 volt standby issue) defect that will cause the nominally 5V stand-by rail to increase in voltages high enough to fry motherboards. While usually associated with older antec PSUs, made by CWT, I could see other CWT PSUs with the same issue. It's due to the circuit design, which when a certain cap fails (the "killer cap"), the voltage control goes wacky. FWIW, bestec also used this design in some of their 250W and 300W units and had similar issues with it (and a similar reputation for fried motherboards)

If you have a multimeter, power the PSU, unconnected to a mainboard, and measure between the purple wire at the ATX plug (5vsb) and any black wire (ground). If it's anything significantly over 5V, then you have a motherboard killer needing a recap and (probably) a fried PII board... and unless and until it's recapped, don't use it...

The power supply had bad caps and a black part of the board around one the resistors were fried too.

I already recapped the thing but am still wondering about the resistors because the colors were fried off.

canadaboy25

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

The power supply wasn't putting out any power before I recapped it.

canadaboy25

[domas]

Re: Busted Pentium 2 Power Supply?

if it is output resistors, i.e.on 3.3, 5 or 12V rails, they have a tendency to get hot. Then it is kind of normal. i do not like it anyway.

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

if it is output resistors, i.e.on 3.3, 5 or 12V rails, they have a tendency to get hot. Then it is kind of normal. i do not like it anyway.

So how would I tell the value of them?

canadaboy25

[domas]

Re: Busted Pentium 2 Power Supply?

they have color stripes that represent their value http://www.digikey.com/us/en/mkt/4-band-resistors.html (change to 3 or 5 band if it is the case)
Please take some time to learn the system, it is really much less complex than it looks like at first. Will be useful for future troubleshooting/projects. You might say it takes a minute to identify resistor, but after dome time it will take 5 seconds.

good luck

[larrymoencurly]

Re: Busted Pentium 2 Power Supply?

Why does the power supply say supports Intel Pentium 4 and supports AMD Athlon?

How can a power supply not suppport a processor?

I think it has to do with Intel and AMD certifying power supplies, about 12-15 years ago, or maybe any supply with a square 4-pin connector for the +12V is considered Pentium 4 compatible, while a PSU that has a single inline 6-pin connector with extra ground, +3.3V, and +5V lines is considered AMD Athlon compatible. BTW nonstandard Dell supplies have the same 6-pin connector, only it's wired differently and is only for ground and +3.3V.

[canadaboy25]

Re: Busted Pentium 2 Power Supply?

they have color stripes that represent their value http://www.digikey.com/us/en/mkt/4-band-resistors.html (change to 3 or 5 band if it is the case)
Please take some time to learn the system, it is really much less complex than it looks like at first. Will be useful for future troubleshooting/projects. You might say it takes a minute to identify resistor, but after dome time it will take 5 seconds.

good luck

Hi, I know how to identify resistors I have been doing it for a long time.

My question is the color rings are burned off so how would I tell the value?

canadaboy25

[domas]

Re: Busted Pentium 2 Power Supply?

oh ok, i didn't get that from the very start
did you try to measure them? If they are something like 10ohm to 100ohm range they are most likely correct. My best guess would be 20ohm for 5V rail and 50ohm for 12V rail.. The less the value the more power wasted and heat generated generated. Or just find some old simmilar p/s to look for an example.

Try some AT P/S from this list as well: http://danyk.cz/s_atx_en.html


good luck