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Old 27 January 2015, 12:15   #1
xArtx
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A500 White Screen

Hi Guys,
I picked up an A500 Rev 6A today.
When powered up I get a white screen, caps lock on for a second, red power LED
keeps flashing bright and dull.. about once per second.

I never see the Kickstart screen, and no disk drive activity.

Funny thing, I have a KS 2.something ROM, and if I use that, the white screen
flashes back to black for a second, so it’s white for about 9 seconds and black for 1 second.
Put the original KS ROM in, and back to white all the time.

The expansion was corroded, and has been removed, but the A500 board looks fine.

Any ideas about this one?
Cheers, Art.
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Old 27 January 2015, 12:25   #2
Jope
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KS2 first initializes the colours as black, so it's normal to have it go black for a while in a reset loop.

So .. do you have any change in the shade of the screen in 1.x? White is the absolute last one, it goes dark grey - light grey - white.
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Old 27 January 2015, 12:30   #3
xArtx
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Hi No, I do remember what the boot looks like.. I think the emulators do it too,
but I just see the nice clean white that never changes.

ps.. I can only look through mono at the moment, but it takes about 0.5 sec to get to white..
so I don’t think the other flickers are happening between.
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Old 27 January 2015, 12:34   #4
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Try removing the chip that are in socket and put back.
Try swap the CIA chp.
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Old 27 January 2015, 12:37   #5
xArtx
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I have re-inserted all chips but Agnus for which I don’t have the tool.
Also tried two other 68k’s. One of mine must be bad because one of them doesn’t even get the screen to white.
Swapping the CIAs I will try.
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Old 27 January 2015, 12:57   #6
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Actually... forget it for now... I can’t be sure it’s white and not one of the diagnosis colours until I get colour out of it :O
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Old 27 January 2015, 13:15   #7
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My guess is a green screen..
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Old 27 January 2015, 13:26   #8
xArtx
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Quote:
Originally Posted by Jope View Post
My guess is a green screen..
Chip RAM? Why do you think so? Is that common?
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Old 27 January 2015, 14:04   #9
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A common cause for that is a corroded Agnus socket.
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Old 27 January 2015, 14:19   #10
xArtx
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Ok, thanks.

It does appear to be green. The green signal from the DB23 is higher than the other two colours.

Quote:
Originally Posted by Jope View Post
A common cause for that is a corroded Agnus socket.
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Old 28 January 2015, 06:46   #11
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The only reason I can tell why it’s working is if some of the through holes for the trapdoor
header are also vias. I only removed the header and touched all of the holes.
It just means if another expansion goes in it, it needs to be soldered , or I need a new right angled
header connector.
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