CMOS battery and the case of the blank screen

[Pyroman]

Heya

 

Having a problem that i can't get my head around.

 

We have some old machines and on one of them, when you switch the machine on, the screen stays blank. If you then remove and put the battery back in, the machine will start fine, screen working, until you restart or switch it off, then the screen doesn't work again until you remove the battery etc etc...

 

I've reseated the RAM changed the HDD changed the battery, any thoughts?

[Pyroman]

Update:

 

Just checked with no CMOS battery atall and the same thing happens only now with the power cable. It looks as though the PC is happy to boot when it's had no power (power cord and battery disconnected) but only on the first time. If you either have no CMOS battery in and leave the power cable attached or have the CMOS battery in and no power lead it'll only boot and switch the screen on first time, if you restart it'll not boot the second time.

 

Only way to get it to boot is to totally remove power before trying to boot.

 

*scratches head*

 

P.s I've also tried this with 3 seperate power supplies and 3 batteries

 

also tried 3 sticks of RAM

Edited April 17, 2012 by Pyroman

[chazzy2501]

sounds like the mainboards are duff. I know you've cleared the CMOS but have you tried loading the defaults to see if it still happens?

[Oaktech]

is there a bios update you can try?

[Pyroman]

Tried both unfortunately, looks like it's going on the scrap pile, it's 5 years old anyway but i hate having to throw stuff out! As much as i can i try and keep stuff running as our budget is pants!

[difinity]

Are you testing out of the case ? And i guess you've checked for leaking/bulging capacitors.

[Pyroman]

Still in the case, i've looked at the caps and 1 looks slightly dodgy, however i've just been shouted to a couple of other calls and pretty much the same thing on 2 other machines so i think this batch of motherboards is slowly dying

[difinity]

Replacing capacitors is cheaper than replacing motherboards, especially is money is tight. Usually about 50p a cap.

[Pyroman]

Replacing capacitors is cheaper than replacing motherboards, especially is money is tight. Usually about 50p a cap.

 

Might have to give that a go, see if my soldering skills are still up to it.

[difinity]

I recommend getting some liquid flux like this NO CLEAN LIQUID FLUX PS3 YLOD XBOX RROD BGA REFLOW 50ml | eBay

and one of these Aluminium Solder Sucker, Solder Vacuum Desoldering Pump, De-soldering Tool | eBay

It will make the job alot easier, especially the flux as it helps with heat transfer.

[Pyroman]

Just as a quick update i've searched google for a similar problem and came up with this http://www.edugeek.net/forums/hardware/83349-scl-pcs-msi-945gcm7-motherboads.html

 

This is my exact problem, should have searched first! Same manufacturer and mobo's.

 

Time to get the soldering iron out!