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Summary
Summary
The Amiga, like most computers, has a cold and warm reset process that is initiated upon power on or upon a triggered reset signal. The various chips used in the Amiga receives a reset signal when this reset process is initiated. If the reset signals do not get propagated to the various chips then Amiga will hang and not boot up.
The schematics found at:
https://www.amigawiki.org/doku.php?id=en:service:schematics
and board views at:
are excellent resources to understand and locate the reset signals and traces.
To better help this understanding and troubleshooting I have created diagrams that shows the various signals and related components and pins. The aim is to provide a single diagram view of the reset signals.
TTL Signals and Logic Probes
TTL Signals and Logic Probes
The Amiga uses TTL logic signals (Low = 0V and High = 5V) and my recommended way of seeing/measuring those signals is with a logic probe. You can buy relatively cheap logic probes from Amazon, eBay or other well known online retailers that looks like this:
They come with crocodile clips that you need to connect the black clip to a GND (0V) source and the red clip to a VCC (+5V) source on the Amiga motherboard.
If you have not got a logic probe then you could use a digital multimeter to measure the voltage of the signal, but this will not be as easy or convenient and you will not have the benefit of the visual and audible feedback that the logic probe provides.
I highly recommend watching this YouTube video on how to use a logic probe:
Reset Diagrams
Reset Diagrams
The reset diagrams currently available are:
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