-----Original Message-----
From: Jon Elson [mailto:elson at
pico-systems.com]
Sent: 01 January 2018 18:07
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: ZX Spectrum Z80 Keeps Resetting
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.
That is interesting, I hadn't considered that. Given that it gets a fair way
into the boot sequence it would have to be an intermittent failure.
Regards
Rob