Amiga 2000 stopped working... (FIXED)

[stephen_usher]

My hunch is that the system is halting as soon as the ROM code tries to do any I/O.

Given that the first thing that DiagROM tries to do is write to the serial port but the Kickstart ROM probably does a memory test first would be why one runs for longer before stopping.

[BennehBoy]

So that circles back to a bus error then? And maybe those LS245s?

[terriblefire]

:!:

My hunch is that the system is halting as soon as the ROM code tries to do any I/O.

Given that the first thing that DiagROM tries to do is write to the serial port but the Kickstart ROM probably does a memory test first would be why one runs for longer before stopping.

But since he's measured ROM /OE and it never goes low it's not. It's not even enabling the ROM to execute code

[Kepler]

This is interesting...if I remove U300 and measure the voltage at pin 2, it reads 0.45v at start up. If I insert U300, it measures 5v at start up...

Actually, now that I have seen and read the previous posts, this is correct behavior.

[BennehBoy]

You said you tried all the custom IC's in another board... what about the CPU? EDIT, although it wouldn't explain OE on the ROM...

[Kepler]

I wish I had missed that and it was the cause of this grief...but it was the first IC I replaced. 😭

[terriblefire]

I wish I had missed that and it was the cause of this grief...but it was the first IC I replaced. 😭

Is there any way you can capture /AS low and ROMOE at gary at the same time on your scope? trigger on the falling edge of /AS once .. if you could hold the machine in reset with the power on beforehand that would be even better.

[Kepler]

Capturing both would require two leads presumably?
How do I hold the machine in reset with the power on?

[terriblefire]

Capturing both would require two leads presumably?
How do I hold the machine in reset with the power on?

Short the reset line to ground until you are ready or if you have a helping hand hold CTRL-AMIGA-AMIGA , set the scope to trigger then let go.

[stephen_usher]

@terriblefire given that the OP is reporting different symptoms depending upon which ROM is installed, do you think it may be a good idea to perform this test without either ROM installed, just in case the fault is being compounded by the ROM chip(s)?