Zx Spectrum 48k vertical black lines on boot problem

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1024MAK
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by 1024MAK » Tue Jul 04, 2017 12:55 pm

It looks like the ULA has suffered from some damage to one of it's inputs.

If it still accepts commands, either type in this simple test program, or if you have another Spectrum, type it in, SAVE it to tape (or other audio recording device), then LOAD it into the faulty Spectrum.

10 CLS
20 POKE 16384,85 : PRINT AT 5,0; PEEK 16384
30 POKE 16384,170 : PRINT PEEK 16384
40 PAUSE 0

If the returned values are correct (85 and 170), then, it does rather look like the ULA chip has been damaged.

ZX Spectrum memory map http://www.worldofspectrum.org/ZXBasicM ... hap24.html

Fault finding guides
http://www.1000bit.it/support/manuali/s ... ec4_2.html
http://www.worldofspectrum.org/SpectrumRepairGuide

Mark

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Paul
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by Paul » Tue Jul 04, 2017 1:27 pm

AmintaSpectrum wrote:
Tue Jul 04, 2017 12:34 pm
Yes, and the only option I have is to "cannibalize" another Spectrum, isn't?
Fortunately there are replacements available.
Unfortunately I am not the one who knows which exact options there are and where to get them.
Could some ZX-Spectrum specialist please help here? I am more into ZX80 :oops:
In theory, there is no difference between theory and practice. But, in practice, there is.

AmintaSpectrum
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by AmintaSpectrum » Tue Jul 04, 2017 1:28 pm

Thanks Mark!

Unfortunately, I think the ULA is the culript...

So I have to buy a new Spectrum to get one?

Thanks!

Image

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1024MAK
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by 1024MAK » Tue Jul 04, 2017 2:03 pm

There are no stocks of original Sinclair Spectrum specification ULAs as far as is known. One repairer has searched many leads and come up with nothing.

However, there is a modern recreation. I have one 8-)

Give me a minute, I'm mobile at the moment and my memory has gone blank...! :shock:

Mark

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1024MAK
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by 1024MAK » Tue Jul 04, 2017 2:26 pm

Ah, memory returned :D

Have a look at the Nebula - A Spectrum 16/48 ULA Replacement Module and the important fitting notes.
Link to shop.

Note that as demand mostly outstrips supply, you have to keep revisiting the shop in the hope that some more have been made.

Mark

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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by AmintaSpectrum » Tue Jul 04, 2017 2:58 pm

Yes Mark,

I knew the Nebula Project, it's only that is not so "philological".... In the end, it's partially emulation... However, if I can't cannibalize another Spectrum, I'll opt for this solution, at the end...

Thanks!

Davide
1024MAK wrote:
Tue Jul 04, 2017 2:26 pm
Ah, memory returned :D

Have a look at the Nebula - A Spectrum 16/48 ULA Replacement Module and the important fitting notes.
Link to shop.

Note that as demand mostly outstrips supply, you have to keep revisiting the shop in the hope that some more have been made.

Mark

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Paul
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by Paul » Tue Jul 04, 2017 3:18 pm

Sorry to interrupt here:
CPLD and FPGA have nothing to do with emulation.
It's a reconstruction on basis of gates like if you took a breadboard with many TTL chips and put all these neccessary wires to remake a ULA.
There is no software involved. No emulation. No delays. Everything in parallel.
It's real hardware. Just really tiny. And configurable.
Im recreating a ZX81 ULA at the moment and it's completely schematics, no line of code included.
Kind regards Paul
In theory, there is no difference between theory and practice. But, in practice, there is.

AmintaSpectrum
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by AmintaSpectrum » Tue Jul 04, 2017 3:23 pm

Perfect Paul, sorry but I've read the word "emulation" on the official description....

Sure I've misunderstood it. "The core has only the features that the original Spectrum ULA has – nothing more (the CPLD is full anyway!). Emulation aims to be cycle perfect – it passes the FUSE tests and runs programs that rely on the floating bus behaviour."

Thanks for your explanation!

Davide

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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by Paul » Tue Jul 04, 2017 3:44 pm

I haven't been on their site yet.
Maybe they speak about emulation because the true schematic is unknown and they Mimik the original behaviour cycle perfect.
I wouldn't speak about emulation but about reverse engineered.
The definition of emulation isn't really fixed.
In my usage it's software that tries to behave like hardware. As it is only sequential (at least not many thousand processes at the same time) it can't be perfect.
There was an emulator that tried to emulate signals instead of behaviour (ZX81 on a mac if I remember right) but that was really slow because there are many signals in a Z80 computer.
In theory, there is no difference between theory and practice. But, in practice, there is.

AmintaSpectrum
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Re: Zx Spectrum 48k vertical black lines on boot problem

Post by AmintaSpectrum » Tue Jul 04, 2017 4:59 pm

Thanks for your useful explanation! Unfortunately now the Nebulas are out of stock...
Paul wrote:
Tue Jul 04, 2017 3:44 pm
I haven't been on their site yet.
Maybe they speak about emulation because the true schematic is unknown and they Mimik the original behaviour cycle perfect.
I wouldn't speak about emulation but about reverse engineered.
The definition of emulation isn't really fixed.
In my usage it's software that tries to behave like hardware. As it is only sequential (at least not many thousand processes at the same time) it can't be perfect.
There was an emulator that tried to emulate signals instead of behaviour (ZX81 on a mac if I remember right) but that was really slow because there are many signals in a Z80 computer.

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