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 The Colored Screen
The Amiga POST (Power On Self Test) is not commonly known to
everyone that uses it.
Unlike the single BEEP code that PC's give, when you turn it on. The Amiga makes no
audible noise when the motherboard has passed its tests. The Amiga does not display a
Happy image like the Happy MAC that Macintosh users find comfort in. The signs that our
beloved Amiga has passed it's POST, is mostly hidden from our sight, that is unless
something has gone wrong.
When the Amiga turns on, there is a series of
self-tests it performs, if it isn't too badly damaged. If the Amiga cannot tell you what
is wrong the Amiga will just give a black or dark gray screen.
Here
is the process that your Amiga goes through when starting up, for anyone interested or who
may need a diagnosis |
| Clear all chips of old data |
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| Disable DMA and interrupts during the
test |
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| Checks to see if 680x0 is functioning |
DARK GRAY: The initial hardware
tested OK. The 680x0 is running. |
| Beginning of system startup |
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| Check RAM at $C0000, and move SYSBASE
there |
WHITE: The initialization test have
has passed. |
| Test ALL CHIP RAM |
GREEN: Error was found in the CHIP RAM |
| Check that software is coming in OK. |
LIGHT GRAY: The software is coming
in and seems OK |
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BLUE: Error was found in the custom
chips |
| Setup CHIP RAM to receive data |
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| Link the libraries |
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| Check for additional memory and link
it |
GREEN: Error was found in the CHIP
RAM |
| Turn the DMA and interrupts back on. |
RED: If
an error was found in the ROM chip(s). |
| Start a default task. |
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| Check for 680x0, and or 6888x |
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| Check to see if there is a processor
error. |
YELLOW: If 680x0 found an error
before the error trapping software (GURU) was running |
| If so, do a system rest |
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| If
your Amiga stops while displaying a color you may be able to fix it without replacing
anything |
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| BLUE: Error in the custom chips = Try replacing one of the chips-- Many times if a
chip is warm it is an indication of failure -- Press down on each chip to make sure they
have not come loose, this is common on early Amigas that have socketed chips. |
| GREEN: Error was found in the CHIP RAM / RAM
chips may not have temperature change, if you can try to replace some chips |
| RED: An error in ROM = Again touch is a
good indication. Sometimes these can come loose though, especially in earlier Amigas. |
| YELLOW: 680x0 found an error before GURU
was running = Check the Memory and the Processor. There are sometimes non CPU factors.
Check the daughter boards and especially the Zorro slot cards (risers) on the A3000 and
A4000 families. |
| LIGHT GRAY: The software is coming in
and seems OK = If it stops here, there is a problem with the software, that does not have
error trapping for it. Try booting to the Floppy drive and reload the OS. |
| WHITE: Initialization test passed = If
it is stuck at this color it did not complete the next step, check your RAM. |
| DARK GRAY: The initial test is OK. The
680x0 is running = If stuck at this point, the CPU may have failed, before color was
changed or there may be another hardware failure. disconnect everything from the system.
Printer/scanner/drives (if you want to open the system the internal too),mouse, keyboard
(on BIG BOX models), and check all ports, and expansion slots. Then restart. Also check
the seating of the 680x0. |
If you have a display without one of these colors, there is more testing to do.
Check for the power light, and listen for the powering sound. Listen closely to it, does
it sound normal?
Use the brightness and contrast controls, or other switches and settings on the monitor
itself.
The best way to test for a dead monitor is to try the monitor on another computer, or
other equipment.
Smell the monitor, when monitors burn out they usually leave a smell.
Try another power cable, even if you have a power light, cables can go bad, and still
power the light.
Check the connection to the computer, they come loose, even without moving the computer.
Plug it into another outlet, without the power strip, even if you get the power light,
sometimes the outlet will have enough energy for the light but will not power the display
of the monitor.
Be sure to check that you cannot replace the fuse. It is better to be out the few dollars
for a fuse, than be out the money for a new monitor, that may have just needed a fuse.
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