Vaio desktop powers on then right back off

[stevenriz]

It's a Vaio PCV-RZ14G desktop PC that when you hit the power button, the fans start up and immediately shut back off again. No bios screen, nothing. I know the power supplies are proprietary but to test, would any power supply work if I just fed the cables to the mobo?

the mobo is a P4S533-VX, probably proprietary too...

Knowing it could be just about anything, power supply, CPU, mobo, do you have any other suggestions on how to narrow this down to the bad part? It's a decent PC so I think it's worth spending a few dollars on.

thanks everyone!
thoughts?

 

[edfair]

The immediate action is a symptom of a "crow bar" shutdown. As the power supply starts to come up excessive current flow in one section sends a signal to shut down to prevent damage.

General troubleshooting is to pull all power supply connections except the motherboard and see if it still fails. If not, then add items back one at a time until you get a failure again. If it fails with just the M/B connected you have something shorted there, the processor has shorted out, or the power supply has issues.

I've generally found that the most likely failures are power supply, modem, CD, M/B, processor, and hard drive, in decreasing order. Others may have had different results.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[G0AOZ]

I'd go with Ed's first suspect - the PSU.

The mobo part number you've quoted is a standard Asus board, so connecting another standard ATX PSU should be straightforward.

But carry out Ed's list of tests first, and check that you don't have a stray bolt or anything jammed under the motherboard shorting it out...

ROGER - G0AOZ.

 

[wahnula]

First step is always strip down to thee basics...then tear down your PC. First test should be ONLY PSU, mainboard (with ALL power headers connected, especially the 4-to-8-pin second connector in addition to the 24-pin main connector.

Disconnect ALL front panel headers and switches from the MB, all ODDs, all HDDs, nothing but MB, RAM & CPU. This should get you to the BIOS screen. If nothing I'm in the bad-PSU camp.

edfair, I've heard you describe a "crowbar" shutdown before, is this because the electronic symbol looks like a crowbar or the actual relay does?

Tony

Users helping Users...

 

[G0AOZ]

In the U.K. the meaning of "crowbar" relates to a shorting out of live and neutral voltage rails. The crowbar as a tool is made of thick, heavy metal which when placed across a potential difference isn't going to melt like a fuse - it's just plain gonna short it out. PSUs have what is called crowbar protection, i.e. they will (hopefully) shut down quickly if a short circuit is detected on any of the low voltage output rails, thereby preventing damage, overheating, fire, etc.

Hope that helps...

ROGER - G0AOZ.

 

[edfair]

When I speak of a crowbar shutdown I mean the electronic equivalent of slapping a physical crowbar across two bus bars. The electronic equivalent is a SCR that shorts the rails. And that is the name for the circuit in the power supply.

Roger's description is accurate except for the fact that the short is thrown across the rails for several reasons beyond a potential short.

It is assumed that for electrical purposes a crowbar across the busses will blow the supply fuses and protect whatever is connected.

I've seen people put a jumper between hot and neutral in a 120v installation to protect themselves if somebody else does something stupid. You get more than one person working on distribution and there is always the risk of somebody activating a circuit. I had one co-worker take off a circuit breaker handle lock and activate a circuit I had been working on. No need to repeat what I told him.



Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[stevenriz]

thanks everyone for this valuable information. I'll get going on some of this over the next couple days. I have a PS tester that should give me some information. I'll report back as well!!

Steve

 

[BadBigBen]

@Steve - if the PSU switch does nothing, then try the CLR CMOS jumper, this does wonders at times... and if that does nothing, then do strip down that PC to it's bare essentials and bread board it (place the mainboard on a table top (non conductive), PSU, 1 RAM stick, CPU and HS fan) and troubleshoot from there on...

IMHO, though, it is not worth spending any money on a S478 mainboard with a SiS chipset, as you can get great deals on newer bundles (CPU&MoBo&RAM)...

@Tony - I grew up in TX (and EU) and I have heard about a crowbar shutdown before, just made me wonder that you did not... oh, and btw. those old ASUS P4S533 boards, ergo Socket 478, only use the 20+4 pin power connectors...


Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[stevenriz]

ok gentlemen, here is what I've done so far.

- with the original PS, the system turns on and shuts down
- if I hold the power button down, it starts and stops about 3 times per second
- I've tested the PS with a tester. All lights came on except the -5v and all connections seem to light their particular light on the tester itself, the 4pin square connector, the 4pin device power connector etc... I don't know that this is a pertinent test
- I then tested a new power supply and all lights for the 20pin lit up including the -5v
- I put that new power supply on the vaio and it turns on and the computer stays on but there is no video post
- since I am fixing another computer at the same time, I thought I'd test its power supply and it lights all the lights except for the -5v as the original vaio power supply does so now my theory that the vaio PS is dead kills the theory

think I should just go for a mobo?

do these tests tell you anything further??

thanks!
Steve

 

[BadBigBen]

Probably the PSU, if it is really dead, took out the gfx-card as it went... but this is just conjecture, as I do not have a VAIO PSU or mainboard at hand to test with...

like I said in my earlier post, it probably would be more economical to purchase another mainboard, and rebuild it...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[paparazi]

You are in one of those catch situations:
This looks to be a minimum PSU/motherboard and possibly graphics card. Trouble is....they are all obsolete so would need saucing second hand or refurbished. Socket 478 motherboards actually command quite a high second hand value so this won't be a cheap repair. This is further compounded by the fact technologies have also moved on ie:
Your PSU has 20pins they are now 24
Your graphics card is 8X AGP they are all PCIe
The memory type on this board is just DDR now we are in to DDR2 and DDR3
The hard drive is IDE, we are now using SATAII
The case is likely not vented particularly well and not to the latest standards....the list goes on.
My advice could be to install an upgrade bundle: Motherboard/CPU/Ram but this would also lead to the necessity of replacing your power supply as well to get the 24 pins and extra power connectors used on modern motherboards.
The other alternative is of course a whole new unit.
Martin

On wings like angels whispers sweet
my heart it feels a broken beat
Touched soul and hurt lay wounded deep
Brown eyes are lost afar and sleep