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ZXNU

Verfasst: 04.07.2019, 21:39
von rune
Hello, I have built my second ZX NU which boots and works OK except for a couple of things:

1 - The first screen is mostly stable, but has rolled so that the bottom line appears at the top.

2 - If I select ZX81 or H4th, the screen rolls in jumps of about 2/3 of a screen .

I've tried changing the Z80 with 6 others which does seem to affect the amount of roll but doesnt cure it.

Can any of the ZXNU guys point me to what could be causing the problem.

Thanks

Dave

Re: ZXNU

Verfasst: 11.07.2019, 20:20
von rune
Problem solved, it was IC14 causing the problem.

Re: ZXNU

Verfasst: 12.07.2019, 12:23
von Joachim
Hi rune!
Was IC14 faulty or wrong type?

Re: ZXNU

Verfasst: 12.07.2019, 13:19
von rune
hi Joachim

it was the LS variant. It gave a perfect picture, but couldnt stop it rolling. The HCT version fixed it.

The Menu screen with black on white didnt roll, but was low by about 8 lines. The white on black rolled badly.

The ZX81 screen jumped in 12 or so line incrememnts, but a loop to print all the characters stopped it and then it was like the menu screen. Stable, but about 8 lines lower with the bottom lines coming in at the top.


Dave

Re: ZXNU

Verfasst: 12.07.2019, 15:51
von Joachim
Hi Dave,
mysterious but good to know ;)

Re: ZXNU

Verfasst: 12.07.2019, 17:12
von rune
Yes, I tried the LS version in both of my ZX NUs and got the same effects.In fact I tried 3 LS versions - all the same.

Also, changing the Z80 between the 6 or 7 I have made the effects more or less worse. But the weirdness was definitely IC14.

Dave