Spectrum +48 Oddities

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RWAP
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Spectrum +48 Oddities

Post by RWAP » Mon Jul 24, 2017 7:27 pm

I have a ZX Spectrum+48 which has exhibited some odd behaviour.

Originally when I had it, the power connector and EAR connectors were both dubious, and I replaced them both. The Spectrum then worked and loaded software and I could leave it running in a demo mode for a game for an hour, but any attempt to load a new game after that time resulted in the Spectrum resetting (until it cooled down).

MutantCaterpillar had a look at it and could not replicate the issue, but to be on the safe side, recapped the machine and added a heatsink to the ULA.

It has been working fine since, but then today has exhibited similar behaviour. Now the machine works fine, unless I try to load a game on it (even from cold). I can enter the normal LOAD "" command without an issue, but as soon as turn on my cassette player (ie switch it on at the mains, or if it is already on, press the PLAY button), the Spectrum appears to reset but then immediately shows an error code (!). The error code is either:

4 Out of Memory 0:1
or
I FOR WITHOUT NEXT, 0:1

If it is the second message, then I cannot do anything until I reset the Spectrum.

Any ideas as to what might cause this? Could it be something as simple as a faulty memory chip ?

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1024MAK
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Re: Spectrum +48 Oddities

Post by 1024MAK » Mon Jul 24, 2017 11:06 pm

That is some odd symptoms.

While it may well be a RAM fault, it could just as likely be a CPU, ROM or power rail / 0V rail fault...

Is it consistent? If yes, do the same thing, but with the cassette player NOT plugged into the wall socket. Yes, I know that sounds strange...!

Mark

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