Dell Optiplex 755 Won't Start

[RVB]

I've been given a 2007/8 Dell Optiplex 755 which has been in storage for a few years. Unknown why it was put into storage.

When the power button is pressed, the fans come on and it begins to power up for a few seconds then switches off again. Nothing appears on the monitor.

I've disconnected various bits (HDD, RAM, CD/DVD, internal speaker, button battery) hoping that one might be faulty but nothing makes any difference.
I checked the HDD and RAM in another computer and the HDD is dead but the RAM works fine.

I'm now wondering if its failure to power up even to a BIOS screen is a motherboard fault? However, it's very clean inside and there are no signs of puffed/leaky capacitors or other worn-out looking parts.

What do you think?

[RVB]

peterperkins said:

Replace the button battery unless it is already new .

Reseat the RAM and try again.

Presumably it will need a working disc drive with OS to boot.

Thanks.
I already tried a HDD from an identical computer with same Windows version (still wouldn't startup) and have taken out the RAM to test in another computer and refitted when it checked out OK.

I will try a new battery later. It's quite likely the battery is low but would it cause a failure to start? Normally the computer will just say 'system battery voltage low, press F1 to continue' before it powers up (or something like that).

[RVB]

Mr Pointy said:

Does this model have a PSU self test button on the back? Give it a press if it does.

Thanks. I'll check that later along with the new battery that's also been suggested.

[RVB]

Durzel said:

From my memory of the Optiplex 755 the green light will come on, then go off, and then a few seconds later come on again. Presumably it doesn't do the second bit?

Yes, green light comes on for about three seconds and then everything shuts down.

[RVB]

Jinx said:

My Dell studio 540s (similar vintage) - won't start at all if the CR2032 battery is dead. Replace and try again.

Tried two different batteries - one brand new, one used, but no improvement.

[RVB]

buggalugs said:

Check the mobo for swollen or leaking capacitors

Everything looks remarkably clean with no swollen or leaking capacitors that I can see.

[RVB]

Mr Pointy said:

Does this model have a PSU self test button on the back? Give it a press if it does.

Can't see a PSU self-test.

[RVB]

anonymous said:

[redacted]

Just tried that and made no difference.

[RVB]

bigandclever said:

Might help .. https://www.manualslib.com/manual/356816/Dell-Opti...

Thanks.
Light 1 comes on very briefly but light 3&4 stay on until it powers off.
That decodes as memory failure.

I swapped RAM with an identical computer and the working computer was happy with the non-working one's RAM, while the non-working one still didn't work with known good RAM.

There are no beep codes unless no RAM is fitted.

[RVB]

bigandclever said:

Just to clarify, only one module?

Otherwise .. “NOTICE:If you remove your original memory modules from the computer during a memory upgrade, keep themseparate from any new modules that you may have, even if you purchased the new modules from Dell. If possible,do not pair an original memory module with a new memory module. Otherwise, your computer may not start properly”.

It has 2x 1GB Kingston in slots 1&2, with 3&4 empty as is often the case.
I swapped both Kingston for 2x 1GB Samsung from another working 755 but it still wouldn't start.

The 2x 1GB Kingstons worked fine in the 755 that I borrowed the Samsung RAM from.

[RVB]

eeLee said:

pull all pullable things from the motherboard - drives + power, CPU, RAM, video card. See if it does the same with nothing connected at all. Then put things in one by one starting with CPU and then RAM and video.

You will then start to understand whether the PSU is toasted or it's something else.

So far I've disconnected everything except the CPU (individually and all at the same time) and it didn't make any difference.

[RVB]

eeLee said:

it seems you're faulting through the possible issues, do you have a donor PSU to test against?

I don't have a PSU without pulling a 100% working computer apart.

[RVB]

Durzel said:

Dells can be a bit funky and esoteric, but what I tend to do in situations like this is unplug everything except the CPU and PSU, and then try booting it. You'd get a load of beeps (assuming it has a speaker, it ought to) but then you'd be further along in diagnosing the thing that's stopping it from coming on at all.

I've disconnected everything as you suggest but it only spends ~3s trying to power up before switching off again. It doesn't get to the part where it might beep.
However, if I try to power it on without RAM it will beep before powering off again, so it is capable of beeping.

[RVB]

eeLee said:

RVB said:

I don't have a PSU without pulling a 100% working computer apart.

can you pull one close enough that you can use the power from it to core components such as mobo?

I don't think the cables would be quite long enough. If it is possible it would be a squeeze and require some careful balancing of one computer edgeways on top of another.

However, I have now removed the power supply from the offending computer and might be able to test it in the other 755 later, since it's easier to manipulate just a power supply unit than to manipulate a power supply still fitted inside a chunky computer.

[RVB]

eeLee said:

RVB said:

I don't have a PSU without pulling a 100% working computer apart.

can you pull one close enough that you can use the power from it to core components such as mobo?

Offending computer's PSU works fine in the other 755.

So I guess we're left with CPU or motherboard?

[RVB]

eeLee said:

with no CPU in mobo, it should at least error in some way, not turn off

So I guess motherboard is the forum's final answer.

[RVB]

BigRuts said:

I don't intend to come across as a douche but is there some sort of sentimental attachment to this a 13/14 year old computer that is driving you to bring it back to life?

Windows XP.

[RVB]

xeny said:

Should I have any surplus XP compatible PCs, and be headed in your general direction, would you appreciate a PM so I could drop a couple off with you?

Yes, I would appreciate a PM if at some point you happen to have some old Dell Optiplex 755 or 760, possibly 780.
I don't mind travelling to collect - we all like driving on here, don't we? But if you see a V6 Insignia being driven like a granny it might be because it has a boot full of old Dells.

The model I find most useful for my XP needs is the Optiplex 755 in what is referred to as 'small form factor' (measures 34 x 31 x 9cm approx).
The 'desktop' version at 40 x 35 x 11cm is a little too large, as is the 'tower' version at 43 x 41 x 19cm.
The 'ultra small form factor' which measures 24 x 24 x 6cm approx seems to have some unknown hardware change which causes some issues with XP and older programs.

The reason I was prepared to try to get the subject of this topic working again was because it is my preferred model for the task I have in mind; Optiplex 755 in 'small form factor' 34 x 31 x 9cm.

[RVB]

Mr Pointy said:

Here you go: £12 for a MB
https://www.ebay.co.uk/sch/i.html?_from=R40&_t...

£16 for an unused one.

Thanks.

Bought one inclusive of processor (for £11 - offer accepted) to cover both eventualities.

Tune in to this topic next week for the next episode.

Edited by RVB on Thursday 24th June 08:46

[RVB]

bigandclever said:

Can't just be me who's nosey for what your 'task in mind' is

Windows XP and programs which won't run in Windows 7/8/10, often due to a combination of operating system, hardware and drivers.