Amiga 4000 Grey Screen #Photos added#

[Aysel]

Hi all, I have posted in the Services Area as I’m looking for someone to repair my motherboard but thought I would ask here in help in case someone has had a similar experience and got to the bottom of it

Amiga 4000 EC030 with a Revision B motherboard, 3.0 Roms, 500mb HD, and no mods or additional cards.

Only bare minimum connected up for fault testing. PSU, Single chip RAM sim, MB, CPU, Keyboard and Monitor.

Power up sequence: Power on, PSU fires up fine, power light green and bright, hard drive light flashes for a few seconds and can hear drive spinning up and reading for a few seconds then nothing, just a grey screen, no floppy drive activity.

Looks as though the battery has leaked a little at some point as the PCB is slightly discolored around it but there is no visible corrosion at all and no fuzzy green stuff anywhere that I can see.

What I have tried:

• Pressed Caps lock, cycles six times then stops suggesting CPU issue?
• Examined CPU card and looks pristine, no visible leaking to any caps etc
• Ensured CPU card is firmly seated
• Confirmed all floppy and HD cables are correctly orientated (also removed both whilst testing)
• Ensured ROM chips are seated firmly and securely
• Examined buster chip and looks to be firmly seated
• Removed all RAM to see if green screen appears... it doesn’t, remains grey
• Left running for a few hours... no change.. grey screen

How did it happen: Installing Octamed onto HD, floppy, desktop and HD all froze with HD light remaining illuminated. Reset and got grey screen... working perfectly up until then.

It’s a very clean machine, all the boards inside are spotless... It’s been in the family 22 years from new so I know it’s never been abused lol.
I’m desperate to get her back to life so any suggestions or guidance would be very gratefully received.

Thanks in advance.

 

[robin-elvin]

Are you certain it's a grey screen and not black? Does it start black and then change to grey? As you are probably aware there is a power up sequence with tests so if it is really grey then it's hanging at a certain part and can give us a clue.
The fact you removed the RAM and get the same means it's not getting to the RAM test part. Have you tried touching all the chips to see if any are hot?

EDIT: Found this: http://www.wonkity.com/~wblock/a4000hard/deadprob.html - could be CPU card or PSU

 

[Aysel]

Hi Robin, thanks for your help.

I turn the monitor on, the monitor screen is black with a green LED, I turn the Amiga on the monitor screen shows a dark grey square covering almost all the screen with a jet black boarder around it and the LED is orange. I have tried the monitor on my A500 and it works perfectly so not a screen issue.

I have left it running for a couple of hours yesterday and could not feel any hot chips.

 

[a.mi.goun]

Maybe CIA is broken.

 

[robin-elvin]

You might want to check the caps in case you have any bulging/leaking ones. If you're going to send the board for repair eventually you may as well remove it from the case and power it up on the bench in case there are any shorts.
Some pictures of the board and CPU card might help too. I'm no expert but I suspect a board that's been ok for 22 years and suddenly dies in the middle of use is going to be either a chip working loose or component failure of either an IC or capacitor. I'm sure roy_bates will jump in at some point

 

[roy_bates]

try removing the harddrive to see if the kickstart screen appears.

 

[robin-elvin]

try removing the harddrive to see if the kickstart screen appears.

I think he already did, Roy.

 

[roy_bates]

inspect the motherboard for bad caps and micro fractures.

check power supply voltages,check contacts everywhere.

 

[Aysel]

Thank you both for the advice.. reading up on the PSU its talking about a 5v supply, can I just check the contacts on the plug coming out of the PSU with a multimeter or should I be testing on the board somewhere?

I have also noticed some odd white fluffy stuff around the base of the long CPU card plug on the MB, its not corrosion so thinking some contact cleaner on the gold contacts on both the MB and CPU card plug is worth a go? I will also do as you say and give the caps a look with a magnifying glass.

 

[vibros]

Hello,

try what roy_bates has suggested: if the kickstart screen come without problems, your motherboard is affected by leackage from battery/capacitors, that has damaged pins or tracks. Take a look at the solder joint of u901 and u902: they need to be shining and not opaque, otherwise there is instability on the contact.

Sorry for my poor english!

Regards
Stefano

 

[Aysel]

Hi, pictures as requested, as you can see a little discolouration around the battery but no corrosion to chips or track lines that I can see... the board and CPU card look really really clean underside is clean too.

Thank you for all the suggestions, I have tried everything above but still just a grey screen so any other thoughts would be very gratefully recieved

 

[Aysel]

Looks like there's light at the end of the tunnel... a very kind offer to test the board and CPU from a local member with some spares then its off to Hikey Monday to see if he can work some magic.

Thanks all for you efforts, greatly appreciated.

 

[johntayloruk]

Old thread but wondered if this was resolved and what the problem was?