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Power not supplied

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by lbsmusica2

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I guess it is back to the 533MHZ CPU 256MEG ram,Via Chipset,dual cpu support,Tyan S1854 Trinity 400 motherboard.It has a PPGA-370 Intel Celeron processor,ATX form factor and supports 8.4 gig and higher. The power supply was a power switch on front and on off switch in back it's gone,was 300 watts. I purchased an ATX power supply,inserted it, turned it on and no power.I purchased it from where I purchased the computer.They know me and my machine.I returned twice because of no power.There is no back switch.All pins are on the way they were before.

25 replies

by arichart

This is probably already been looked at, but are the jumper settings for the power (LED, reset, etc.) in the correct places?

by lbsmusica2

You see,when removing a power supply,there is no need to remove the front casing or the button switches from the board.

by lbsmusica2

Poster rated this answer.
Yes all the pins are indeed in the right places.Pinouts are:1,3 HD LED,2 POWER LED and 4 SLEEPLED,5 GROUND and 6 POWER ON/OFF,7 RESET and 8 GROUND.PIN 13 can be used if a 3 pin bicolor is available with power led.1,3,5 odd top,2,4,6 even is bottom.

by thechas

Just for clarity, an ATX system uses a 20 pin double row connector to connect to the motherboard.
While there may be a power switch on the power supply itself, an ATX power supply does NOT connect to the front panel power switch.

Check the 120V 240V switch on the power supply, and verify that it is in the correct position.

Unless there is a power switch on the supply itself, an ATX power supply is part way on ALL the time.

There is a 5 volt standby power line that supplies power for the power control circuit and a few other functions on the motherboard.

For an ATX system, the front panel power switch is a momentary contact push-button switch that connects to the motherboard using a 2 pin header connector.

To check an ATX power supply, measure the voltage on the Purple wire (pin 9) to ground (any black wire)
With power applied, but the PC off, there should be 5 volts DC on the Purple line.

If there is no 5 volt standby voltage, there may be a short in your system that is blowing the fuse inside the power supply.

Chas

by lbsmusica2

There is no need to check the old power supply it is finished.The new power supply works in another machine,but not the Tyan dual cpu machine.The hard drive blew as well with the old supply.The new supply carries the same pinout for the motherboard.The option of a 2 pin power con or a 3 pin if it had one.That was power switch on power supply back only.Not on front of machine.

by lbsmusica2

Poster rated this answer.
The 20 pin connector that connects to the motherboard fits snuggly with no signs of life,when the front power on switch is pressed.There is sufficiant power from the line that runs the 5 volt fans,but nothing works.What of reverse polarity or parity errors.Could this have happened to the board?

by sgt_shultz

well, the power supply is set to 110, not 220, right? does it have a fuse? does the fuse ohm out? if you just set the power supply on a bench, plugged in, with a hard drive plugged into it (becausde switching power supplies need to have a load before you can measure voltages), when you switch it on, can you measure any DC on any output pins? if so, chances lean towards power supply being ok. or, easier, maybe, can you try the power supply in another computer? if you have been thru two power supplies, i'd start looking at the motherboard instead as problem point...you getting any led's lit on motherboard? have you reseated the processor, RAM? have you taken out all cards and hard drives?
i have two dead motherboards here...the led's light up but they act just like the power supplies are dead. i know the power supplies are ok because i swap them into other pc's and they work...i have no idea how to approach troubleshooting the mboards beyond what i mentioned above so would like to hearhow you make out fixing yours...

by lbsmusica2

Power supply is fine in another machine.All leads are fine as well.The day it went,I removed all items from the board and had put the board through all tests.It is fine.Maybe the Dual cpu,Riser one and the Ziff are needing more power to work.Meaningdual board.Yes it is 110-115v,no fuse.Only one cpu can be used at a time,up to 1.6 ghz.

by lbsmusica2

Poster rated this answer.
The bios has bit the big one.I sat in ahh as I watched my two year old boards bios turn black in the center.The crystal in the award bios has turned back to coal.I thought this time I had finally fix something.It seems peoples help has not been good today.I tried to set it up barebones,just the hard drive,motherboard,memory,cpu and video card.All attached to the wonder dok case it came with.The power connections were done right,the way the board read.I pluged the machine in,pushed the power button,nothing,again and saw the center of the bios blacken.I unplugged all,saaad.

by thechas

Since you know the power supply works, I suspect that when the other supply went, it damaged the motherboard in addition to the hard drive.

When you start up an ATX system, the motherboard sends a signal to the power supply to turn on the main power.

If the power supply does not receive a power good signal shortly thereafter, it shuts down.

Further, 300 watts would be the bare minimum supply for a dual CPU system.
I would go to at least 500 watts.

Take a close look at the capacitors, resistors and transistors near the CPU sockets on the motherboard.
If ANY parts are bulged, charred, or singed, the motherboard is toast.

Chas

by lbsmusica2

The power does not even budge.Nothing,zip,and no.The store says 200 watts is all I need.As long as it meets standard revision 2.01 and ATX. The board tested fine.There is a rainbow color to some pin terminals and a sweet odor to the board.The res,caps, and chips I am not sure the color before.None are charred though.

by lbsmusica2

Poster rated this answer.
There is one thing I have not check for,parity error or maybe polarity error.Polarity errors can not be checked by machines but parity is onboard at boot up.I can not bootup.So how to check for polarity errors.The omhs is plus, the watts is plus.No volts -,so the voltage regulator needs to be checked.I am out of options.

by thechas

Okay,

The power supply is good.

You say the motherboard is also good.
How have you verified that the motherboard works properly?

If you have an ohm-meter, you can check that the front panel power switch works properly.
When the button is pressed, the resistance between the 2 leads from the switch should be nearly 0 ohms.

Next, use a multi-meter to check the power supplied to the motherboard.

Pin 9, the purple wire should have 5 volts DC on it any time the power supply is plugged in.
(All of the black wires are ground.

When you press the front panel power button, Pin 14, the light green wire should go low (nearly zero volts).

If the 5 volts is not present on pin 9, the motherboard is loading down the standby power toheavily. There is likely a short somewhere.

If pin 14 does not go low, then the power control circuit on the motherboard is bad.

If pins 9 and 14 function properly, and the power does not come up, then there is a device connected that is loading down the 3.3 or 5 volt supplies so heavily that the power supply shuts down as it powers up, before enough voltage is developed to even spin up the fans.

I would unplug the power and data cables from ALL drives, and have just a video card plugged into the motherboard. If power now comes up, one of the other devices is the cause of the short.

Chas

by lbsmusica2

Poster rated this answer.
You see the power on the purple is 5v,green is 2.3v but the power stays the same.There is a 8 meg agp video card attached.Rarely used onboard video and sound(builtin)also had usb key and mouse.Could any of these be using the power.The 3v battery is also dead(holds mem.)I think that does.Power fluxuates when power button pushed to start then dies.When it did start the monitor did not move from standby to on.

by stuart_at_oz

IF the new power supply is good, then it's unlikely you have a problem with polarity or connections.

If the old power supply took out the harddrive, then it probably took out something else as well. Most likely the motherboard, but it might also be the CPU(s) or memory.

Will the motherboard normally run with only one CPU? Try it with one, swap 'em and try again.

You also may have blown the mother AND the CPU's, but that depend heavily on the size of the spike the power supply sent down the line. (And sometimes, on the motherboard - I believe some motherboard/CPU combinations tend to go out in sympathy. No sorry I don't know which)

'luck.

Stu

by lbsmusica2

Poster rated this answer.
If you mean a big thunder clap,you gotter,smoke show too.The sparks and flames were scaryer though.But the board,cpu,video card, memory,all checked out fine.After all the smoke cleared the harddrive started to bootup and that is when that blew,with a flash and the cd-rom started smoking.I always leave the side cover off,so I can hear the sounds. better.

by rcom

Try this. Remove the mother board form the case and set it up on the bench. Just install CPU, video and ram. Connect the pwoer supply, try to start it up by physically shorting the 2 pins on the MB that the front power switch connects to with the tip of a screwdriver? Just touch and let go. By doing this you can eliminate the possibility that something is grounded to the frame.

Reset the CMOS.

by thechas

2.3 volt on the power start line is not good.

It should be nearly 5 volts when the PC is off, and close to zero volts when you turn on the PC.

From what we have gone through on this, I strongly believe that the motherboard is bad.

It is possible that the motherboard was stressed when the old power supply died, and just took a few more startups to finally die.

Chas

by lbsmusica2

Poster rated this answer.
Yeah,it is now coal city.See other comments.Some other screw driver trick took care of it.Good thing I have three boards and three bios.I can only follow certain advise and try all possibilities.This is how I had learned to trust my own judgement and gut feeling when it comes to computers,they are like tempered children.Baby them and they play nice,yell and they act bad.Not to hot not to cold,nonstatic,nonvolitile.You have to have intuition.I will succeed.You have helped Chas,thanks.Can you see comment dated 08/06/03 after answer 3.Starting over,get back to me with that.You got it.

by stuart_at_oz

You have said the board, CPU, mem & video card checked out OK - you have had them running ok somewhere since? How did you check them?

(If your HDD & CDROM started smoking, I would be suspect of everything else too.... Takes a fairly good overload to do that methinks.)

Stu

by thechas

After reading the comments, I still come to the same conclusion, when the old power supply went, it stressed the motherboard.

What often happens when a PC power supply dies is that the voltage from the supply spikes up to 2 or 3 times the normal voltage for the supply.
The 5 volt line could have been at 15 volts, the 12 volt at 36 volts.

This over-voltage stresses electronic components in a way similar to static discharge.
The part is now weakened, and will fail before the end of it's normal life expectancy.

I have seen photographs of the microscopic damage to an IC from electrical over-stress. It looks like a bomb went off inside the part.

Nearly all motherboards have additional on-board voltage regulators that drop the 5 volts from the power supply to lower voltages needed for some of the ICs.
Unfortunately, when these fail, they often fail in short circuit mode and place the full input voltage onto the parts.
After that, it is only a matter of time until a complete failure.

Chas

by lbsmusica2

The Chas was a helpful part in the determination for me to go on and get this machine to work.The machine is not working yet but by the end of sept. I will make it work.The answers,some helpful some not and some I can not use.

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