ZX Spectrum Z80 Keeps Resetting

Rob Jarratt robert.jarratt at ntlworld.com
Mon Jan 1 14:56:53 CST 2018

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Adrian
> Graham via cctalk
> Sent: 01 January 2018 20:45
> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
> Subject: Re: ZX Spectrum Z80 Keeps Resetting
> >>>
> >> 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.
> I’d be interested in putting my diagnostic ROM on that just to see what it
> throws up. In the absence of having it in front of me so I can do that is the ROM
> socketed? You can easily burn your own if so.

The ROM is not socketed. I have found that every time I desolder something from this board I end up damaging the through holes, just the suction from my de-soldering gun was enough to remove the "eyelet" today when removing a capacitor. I could socket it though as that would be useful anyway, and I can check the ROM contents and make sure it reads OK multiple times.



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