Desktop PC relucant to switch on!

[#1]

BIOS is the first thing to wake up, it tells the box of bits you have that its a computer.  Listen to the error codes.  When you boot your PC, there should be one short beep.  If you have that, leave the damn BIOS alone.  Watch the screen to look for any error messages that may or may not flash up, they could only be there for less than half a second.  I'm still in favour of a hard drive issue.

[#2]

A hard drive issue would be easy to check for - simple unplug all drives and see if the problem persists. You should still get to the BIOS with no drives connected.

Since the PSU has already been replaced, I expect it's a motherboard (or perhaps CPU) hardware failure. We've had at least one AMD-based system die like that, but that was a few years ago and it was pretty old by then.

[#3]

The screen doesn't light up - even if I switch it on a few seconds before applying power to the PC.

Also no beeps.

Also holding F2 down (to enter the BIOS setup) is (usually) unresponsive.

I can boot from a Blu-ray if that's any help?

I wonder what booting FreeDOS from a USB with a MBR to a UEFI BIOS with a priority of booting from GPT/EFI disks is going to do?

BTW It seems very convoluted to put FreeDOS onto a USB (but possible).                                     

[#4]

---

@ejs wrote:

A hard drive issue would be easy to check for - simple unplug all drives and see if the problem persists. You should still get to the BIOS with no drives connected.

Since the PSU has already been replaced, I expect it's a motherboard (or perhaps CPU) hardware failure. We've had at least one AMD-based system die like that, but that was a few years ago and it was pretty old by then.

---

Thanks @ejs - but it's intermittent and not totally dead yet.

[#5]

When you had the case open, did you try pulling the power switch connector off the pins and using a screwdriver to short them? I keep a "salvaged" switch/lead for use with motherboard "out of the case" testing (the boards don't bend with AMD heatsink fixings )

 Phil

[#6]

---

@VileReynard wrote:

When I switch my PC on, more often than not, it does not fully power up.

The fans spin up, as do the disks and various LEDS (including the on/off switch).

If all the disks and fans power up, surely it can't be a problem with the switch?

[#7]

I'm afraid I didn't try shorting any pins because there were loads of different pins coming from the front of the PC and there didn't appear to be any apparent method of removing the front of the PC. I know you are supposed to be able to short 2 pins of the ATX power connector - but it seems easy to get it seriously wrong.

[#8]

---

@shutter wrote:
what could possibly go wrong ? ) 

---

---

Er, PEBCAK...

Anyway, enough of "its the power switch" nonsense (never let software guys work on hardware!), simple things to do when looking for a fault:

1. Unplug all peripheral hardware (USB devices, PCI cards, SSD/HDD & ODD, etc.) leaving just a keyboard, mouse and monitor, then try again, if it works first time every time, put things back one at a time 'til it breaks again.

2. if that fails to sort it, remove the RAM and reinsert one stick, if it starts fine on one, try the next, until it breaks again.

3. If memory shuffling doesn't change anything, remove the graphics card and try another (if you have one to hand).

4. If that doesn't work, unplug from the mains, press the power button to drain the caps off, and reset the BIOS using the "CLRTC" jumper just above the front panel connections.

5. If that doesn't work either, put everything back in as it was, get it to boot up, update the BIOS and try again.

6. And if all else fails, pay someone else to do it, cos giving out free advice that is ignored gets tedious...

Yes, this involves a bit of work inside the computer I know, but, it's that or pay a tech to do exactly the same...

[#9]

---

@twocvbloke wrote:

---

@shutter wrote:
what could possibly go wrong ? ) 

---

---

Tongue in cheek comment... as Foxy has been prevalent in the past few years on how wonderful and infallible Linux is, comparative to Windows... 

Moderator's note by Mike (Mav): Quote fixed.

[#10]

---

@VileReynard wrote:

BTW Trying multiple on/off cycles (up to 7 or usually "cures" the problem.
This is a recent occurrence in a two year old PC.

---

Could it be the effects of a low CMOS battery level?

This has similar elements to a problem I had with a laptop, where not changing all ( 6+  ) references to hibernation to off depleted the main battery below the "charge" threshold. Repeated "on" attempts pulsed enough charge into the battery for the charge parameters to be readable by the charging circuit and the laptop then started and fully charged the battery.

I also had a strange effect with a desktop set to "lazy startup mode" - it was set to "restart after power fail" and turned off at the mains socket when not in use. Switching the socket on would automatically power up the system However, it suddenly started powering up a few minutes after shut-down, if the socket had not been switched off, which was the result of a low CMOS battery. Not low enough to corrupt the BIOS data, but low enough to stop the clock (which was reset through NTP) and trigger the "power fail" circuit.

Phil

[#11]

Highly unlikely to be the battery, it would still boot, just not with what the box of bits we call a computer.  Pop the case, take a look at the small capacitors around the CPU socket.  Do any of those appear to bulge on the top?  They will be around 1/4 of an inch in diameter and about 5/8 of an inch tall, possibly with a black plastic sheathing shrink wrapped on them with white lettering.  They will also have what looks like a letter 'Y' stamped in the bottom and that's where the bulge will appear if it is indeed present.

[#12]

Again since it is only 2 years old it shouldn't be the caps, unless it was a really cheap board,
WRT cmos battery common fault on mac's that one, esp. the early ones. LCII etc.
Now foxy, you say it will boot from blu-ray, does that mean you CAN boot to a bios screen or are we still talking about no screen at all?

It might be worth resetting the cmos, near the battery there is usually a jumper switch, move the jumper to the alternate set of contacts, power up/off. Reset the jumper. Then try it.

[#13]

I've had caps blow on boards that are less than 2 weeks old.  I'm not that experienced mind, I've only ever built around 5,000 PC's and repaired some 17,000 odd so I'll bow out from this and leave it to your superior knowledge.

[#14]

Couldn't see any obviously blown capacitors.

I have always left the PC plugged in to a live power supply and switched on. I have a pretty UEFI BIOS which I go into every few weeks so I can tell it it to boot using USB to load an in-memory Linux. This allows me to make a backup of my hard disks to an external USB disk, with no file locks in place.

Booting seems to work OK if I tell the machine to re-boot, even though this momentarily removes the power (the disks spin down).

[#15]

@adrianscotter Well yes from NEW I have had the issues, what I am saying is that after working for 2 years it is unlikely to be the issue. Classic bath tub diagram, if it is going to fail it is more likely at the start or well in to the end of life.

How ever, if like me you have worked in a capacitor factory in a technical role, then I will bow to your knowledge.