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Dell Optiplex 745


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6 replies to this topic

#1 eranda gunasinghe

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Posted 02 November 2015 - 03:25 AM

Power light blinking after press the power botton and cpu fan spin once and won't pc turn on....

 



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#2 RolandJS

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Posted 02 November 2015 - 05:00 AM

There might be a short somewhere.  Have you tried removing all peripherals, save KB?  If still nogo, you might have to unplug some internal things such as cd-dvd drive, etc., save HD.  If still nogo, carefully unplug everything, leaving only power supply, motherboard.  Add each stick memory one at a time, add back a device until a successful post and boot -- hopefully into HD.  Reason for suggesting all of this:  sometimes a real good careful re-seating was all that was needed, sometimes a device goes bad and must be replaced.


Edited by RolandJS, 02 November 2015 - 05:04 AM.

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#3 dc3

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Posted 02 November 2015 - 09:07 AM

What is the make and model of this computer?


Edited by dc3, 02 November 2015 - 09:07 AM.

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#4 rqt

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Posted 02 November 2015 - 09:31 AM

Old Dell machines sometimes do this flashing power light thing - & sometimes the problem is the power supply unit (other times it appears to be the motherboard). If your OptiPlex 745 is a Mini Tower or a Small Format Factor case you can use a standard ATX power supply to test the rest of the machine. The ATX power supply will not fit into the SFF case but the connections are the same apart from the optical drive. I would expect the Desktop case to use the same power supply connections as well, but I have not worked on one of these. If you have the Ultra Small Format Factor case then you would need another Dell PSU for testing.

 

If the fault is not the power supply then it's probably easiest to just replace the machine as used Dell OptiPlex machines of the 745 era (& upto  at least the 760) are widely available at low prices (in Europe & the USA at least). It would probably cost me about £20 for a used 745 motherboard, but under £30 for a complete 745 machine (although probably without a hard drive).


Edited by rqt, 02 November 2015 - 09:37 AM.


#5 dc3

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Posted 02 November 2015 - 10:04 AM

Well... I missed the title.

 

The blinking amber power button either indicates a problem with the PSU or the motherboard.

 

rqt has suggested using a ATX PSU to test the system.  The problem is if this is a non ATX PSU then the 20/24 pin connector may not have the same pin configuration as a ATX motherboard.  So if you try to test the motherboard with a ATX PSU you will probably fry it. 

 

This computer was originally released in 2007, so this computer's technology is eight years old.  I would suggest that you would be better off investing in another computer rather than investing in this relic.


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#6 rqt

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Posted 02 November 2015 - 10:24 AM

I did (about 3 years ago so I can't remember whether the OptiPlex has a 20 or 24 pin connector) check the wiring of the OptiPlex 745 SFF power supply against a standard ATX power supply & having satisfied myself that they were the same I used an ATX PSU to test an SFF machine (without frying anything). The Mini Tower PSUs are just ATX anyway (although the motherboards boards are a Dell variant of BTX).


Edited by rqt, 02 November 2015 - 10:25 AM.


#7 dc3

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Posted 03 November 2015 - 11:09 AM

The following is an excerpt from an article titled "Dell proprietary (non-standard) ATX design".
 

It seems that starting after September of 1998 Dell defected from the cause of industry standardization and began using specially modified Intel supplied ATX motherboards with custom wired power connectors. Of course they also had custom power supplies made that duplicated the non-standard pinout of the motherboard power connectors.
 
An even bigger crime than simply using non-standard power connectors is that only the pinout is non-standard, the connectors look like and are keyed the same as is dictated by true ATX. There is nothing to prevent you from plugging the Dell non-standard power supply into a new industry standard ATX motherboard you installed in your Dell case as an upgrade, or even plugging a new upgraded industry standard ATX power supply into your existing Dell motherboard. But mixing either a new ATX board with the Dell supply or a new ATX supply with the existing Dell board is a recipe for silicon toast. How do you like your fried chips, medium or well done?
 
Basically, if you have a non-ATX PSU the pinout for the 20 pin connector is not the same as a ATX PSU, this means that the motherboard will mirror the non standard pinout configuration.  Because of this there is no way you can mix ATX PSUs or motherboards without without damaging one or both components.
 
This only applies to power supplies that have the 20 pin power connector.  So this does not apply to the Dell Optiplex 775 computer as it has the 24 pin connector.

Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.

 

 

 

 





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