Amiga 2000 Boots in 1.2 and 1.3 not in 3.1

ElAhrairah

Member
Joined
Dec 4, 2019
Posts
30
Country
Netherlands
Region
Utrecht
Hi people,

I don't know what to do anymore. :(

Amiga 2000 rev4.2 boots with KS1.2 and 1.3 but when the KS3.1 is inserted the powerled blinks 6 times and the computer restarts, the screen stays black.

- I tried 2 different 3.1 KS, that do work in other Amiga's.
- removed all roms, cleaned.
- removed and cleaned all chips
- test the psu, the voltages are good
- tried feeling if some of the roms got hot, they all remain normal.
- games work under 1.3 with floppy. Workbench 1.3 also is bootable by floppy, no weird issues or glitches.

There is no battery leakage, battery was removed long time ago, the pcb really looks in excellent condition. The cpu pins, and all other rom pins, are in excellent condition. No corrosion.

I'm really confused, especially with the powerled blinking 6 times. And the fact that 1.2 and 1.3 works but 3.1 doesn't.

Thx
 
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Perhaps the high address pin (A17 is pin 1 on the ROM) is unconnected on the MB for some reason? On A500, earlier revisions do not support 512K ROMs without modifications but I am not sure if this is also the case for A2000. I have been using a 512K ROM (DiagROM) in my rev. 4.2 A2000 so I do not think that should be a problem.

Edit: If you have a continuity tester, you can test for a connection between the ROM pin 1 and the 68000 pin 46.
 
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After more testing, changing chips, I finally found out that it's the CPU chip who's the culprit!
I got hold of a few other CPU's and they all booted with every KS rom.
 
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it "might" not be the cpu, I dont know about A2000 but on some A500's ( I found this out when trying 3.1 1.3 kick switch ) Commodore to save less than $1 failed to fit the inline resistor packs around the CPU.

to get around this a special HC version 68000 cpu needed to be fitted, With the HC68000 CPU the inline resistor packs are NOT required for replacement eeprom kick 3.x or switcher to work.
 
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