Random colour in A2000

[Franchute13]

Hi!

I'm repairing a A2000. All chips were tested in A500 Rev 6 (except the Fat Agnus).
Turning on the A2000 I have different colored screens.
Examples:
Black-> Red, and so in a loop
Black-> Red-> Yellow (loops)
Black-> Gris-> Yellow (loops)
Black-> Green
Black-> gray> purple (I guess that is the background color of Kickstart 2.0)
So, random color
It can also be combination in all groups.

The electrolytic capacitors were changed.
None of the chip gets hot.
Any suggestions?

[Franchute13]

Hello.
Currently the computer does the following.
I turn on the A2000: Red Screen, dark gray, Yellow. Then make a loop of the dark gray and yellow.
If I reset using A A crtl , red, dark gray, the Yellow. Then makes a dark gray Yellow loop.
The ROM was tested on an A500 and working properly.
Any suggestions?

[Franchute13]

Originally Posted by Franchute13

Hello.
Currently the computer does the following.
I turn on the A2000: Red Screen, dark gray, Yellow. Then make a loop of the dark gray and yellow.
If I reset using A A crtl , red, dark gray, the Yellow. Then makes a dark gray Yellow loop.
The ROM was tested on an A500 and working properly.
Any suggestions?

Hello.

I could find the problem !. The M6242B chip. Cut the leg (18) goes to + and now the machine works fine

[Franchute13]

Hello.
I still have problems.

I have an A2000 Rev 6. Originally comes with 1MB of RAM on the motherboard.
We also have installed a Megachip
http://www.bigbookofamigahardware.co...t.aspx?id=1941

If the Megachip is installed, the machine starts but only see 2 mb.

If the Megachip not installed, the machine will not boot, white screen but hear floppy disk looking for disquette. If I insert a floppy, read and then hangs. (screen always white.)

Any suggestions?

[watsonfmly]

If you had 1mb and installed the megachip, you will only see 2mb (all chip ram). That part is normal.

[Franchute13]

Originally Posted by watsonfmly

If you had 1mb and installed the megachip, you will only see 2mb (all chip ram). That part is normal.

Hi watsonfmly!
Thanks for your reply.
So, A2000 works

Thks

Originally Posted by Franchute13

Hello.

I could find the problem !. The M6242B chip. Cut the leg (18) goes to + and now the machine works fine

How did you work that out? I'm interested as I have a board which only shows a black screen after battery leak damage. I've done some repair and my next stop was 74 logic.

Thanks

[Franchute13]

Originally Posted by robin_elvin

How did you work that out? I'm interested as I have a board which only shows a black screen after battery leak damage. I've done some repair and my next stop was 74 logic.

Thanks

Hi Robin.
First, you should check the chip (CPU, Paula, Denis, etc) in an A500 to see if they work.
Second, connect the power LED to see if it makes any flicker.

Remember that the battery acid must be neutralized (lemon juice and then wash with hot water)

Perhaps this helps to repair.
http://www.amigawiki.org/dnl/schematics/A2000_R6.pdf

Hi,

I've done quite a bit of checking and the custom chips are all fine. Yes, I know about neutralising the battery leak.

I was just thinking the memory path was damaged when I found your post and wondered how you decided the clock IC was at fault. It might help me.

Thanks

[Franchute13]

Originally Posted by robin_elvin

Hi,

I've done quite a bit of checking and the custom chips are all fine. Yes, I know about neutralising the battery leak.

I was just thinking the memory path was damaged when I found your post and wondered how you decided the clock IC was at fault. It might help me.

Thanks

Hello.

Add some photos of good quality.

Black Screen is not memory problem or memory traces cut. Maybe a CPU o Agnus problem (Bad socket or trace cut.).

The power LED light makes some flicker?

Bye