A good customer sent us their Amiga 600 which was not booting. They had gone through reviewing various signals, like _RST, checked voltages and so on. They saw that the 555 was not putting out a proper signal, but couldn’t sort it out. That’s where we come in!
We started by confirming their issue, which we did; It would not start. Now sadly this post is going to be a bit short and not very climatic. I simply pushed down on the 555 and it immediately booted. I went ahead and applied flux and reflowed the chip, it continued booting without any intervention.
What should you check when your 600 does not boot?
- Look at the output of the 555, make sure it is properly changing output
- If the 555 is corroded, replace it
- If the 555 has dry solder joints, add flux and reflow.
- Using https://amigapcb.org or Amiga 600 schematics follow the path of the KB_RESET signal
- Look at the RESET signal on the CPU, also look at the HALT signal
- Q511, these can go bad due to capacitor leakage. This can be replaced with almost any NPN SOT-23 transistor.
This is a general process, if you’re unable to get your board to boot we’re available for repair.