ULA revision

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LoadError
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Joined: Thu Apr 29, 2021 12:45 pm

ULA revision

Post by LoadError »

Dumb Q: is there any peek-y way to determine which ULA revision one has onboard without opening the case? Every time I have to open up one of my ZX* I fear tearing the keyboard flat cable... because it happened :oops:
My Sinclair belongings:
- unexpanded, unmodified, unbackporched ZX81
- expanded (from 16K to 48K) rubber keyed ZX Spectrum
- a Cambridge Scientific pocket calculator
gozzo
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Re: ULA revision

Post by gozzo »

dont think so, theres ways of telling what rom you have or if you have the rom fix board, but not ula, as far as i know, generally issue 1 boards will have 2c158 or 2c184 ulas, issue 3s 2c210 , but not necessarily always! you can tell board issue by looking in the expansion slot, if theres a transistor and few other components to the left, looking in rear keyboard facing up, its an issue 3
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Paul
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Re: ULA revision

Post by Paul »

You can tell the 2c210 from earlier versions by analysing the video signal. With back porch it's 2c210, without its an earlier versions.
Which earlier version isn't important because there is no significant difference. And none will be worth a fortune.
In theory, there is no difference between theory and practice. But, in practice, there is.
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LoadError
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Re: ULA revision

Post by LoadError »

Thanks, I'll use this info to try and determine the revision, but it has to be an early one because if I hook the machine to any modern colour TV I get a black image (so, no back porch).
I have a restrain order to keep at least 10 mt. away from any soldering iron, so I will need to find someone to do a composite mod for me :D
Plenty of options in UK I guess, but here in Italy it's another story.
My Sinclair belongings:
- unexpanded, unmodified, unbackporched ZX81
- expanded (from 16K to 48K) rubber keyed ZX Spectrum
- a Cambridge Scientific pocket calculator
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BarryN
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Re: ULA revision

Post by BarryN »

LoadError wrote: Wed May 05, 2021 4:03 pm Dumb Q: is there any peek-y way to determine which ULA revision one has onboard without opening the case? Every time I have to open up one of my ZX* I fear tearing the keyboard flat cable... because it happened :oops:
If your keyboard cable is that delicate, perhaps it's time to replace the keyboard?

https://www.sellmyretro.com/offer/detai ... rane-37048
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LoadError
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Re: ULA revision

Post by LoadError »

That happened years ago with my Speccy, and I ended up changing the flat cable, but at the time i didn't know replacements were readily available, so I was in shock :shock: :lol:
My Sinclair belongings:
- unexpanded, unmodified, unbackporched ZX81
- expanded (from 16K to 48K) rubber keyed ZX Spectrum
- a Cambridge Scientific pocket calculator
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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: ULA revision

Post by 1024MAK »

The ULA does not have any memory location that can be accessed with PEEK. And the ZX81 BASIC does not have either the IN (INP) function or the OUT command. And even if it did, that would not tell you which ULA version is in the machine.

As Paul says, the last version generates the back porch part of the video signal. But the only known way to tell the earlier versions apart for certain is to read the details visually from the chip package.

However, a lot of the first ZX81 boards that use the first (2C158) have it directly soldered in. Unless it’s a kit build...
Whereas, most boards that use the later ULAs have them in sockets.

Mark
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