ZX Spectrum Z80 Keeps Resetting

[Jon Elson]

On 01/01/2018 11:22 AM, Rob Jarratt via cctalk wrote:
> I just replaced the last of the electrolytics, but the spikes on the Z80 5V
> rail have not gone away. They only exist on the 5V rail in close proximity
> to the Z80, other chips with a 5V supply don't have the spikes on the 5V
> rail.
>
It could be caused by bus contention, which may also be the 
cause of the resetting.  Possibly some of the
decode logic has failed, and is allowing two devices to 
drive the data bus at the same time.  I've seen this
before, and it does cause spikes on the 5V rails.

Jon