Search found 337 matches

by McKlaud
Thu May 17, 2018 10:54 pm
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123687

Re: ZX81 ULA-in-a-CPLD

Image
by McKlaud
Wed May 16, 2018 10:04 pm
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123687

Re: ZX81 ULA-in-a-CPLD

I am impressed with your progress, Andy. Well done and the board looks stunning. :geek: :geek:
by McKlaud
Mon May 14, 2018 12:28 am
Forum: Hardware
Topic: 28C64 in 2364 socket (28 pin to 26 pin)
Replies: 10
Views: 5423

Re: 28C64 in 2364 socket (28 pin to 26 pin)

Hi Martin,

Have you managed to squeeze your board inside the Zeddy case? I went to the SMD route and still the board a bit too fhigh. I should buy some flip-pins and try them.

Image
by McKlaud
Fri May 11, 2018 10:12 pm
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 63
Views: 39432

Re: zx spectrum in zx81 case

Do you have an oscilloscope? If so, check 14MHz (74HC004 - pin8) & 3.5MHz (Z80 clock - pin 6) signals on the board and also the Csyns signal on to pin 8 of miniDIN8 socket.

If you touch with a finger the bottom of your board near the 74HCU04 is anything changing on the screen?
by McKlaud
Sun May 06, 2018 7:52 pm
Forum: Development
Topic: ZX Printer Belt
Replies: 139
Views: 85870

Re: ZX Printer Belt

Mark, much appreciated. Anything (any parts) for ZX Printer are welcome.
by McKlaud
Sun May 06, 2018 5:05 pm
Forum: Development
Topic: ZX Printer Belt
Replies: 139
Views: 85870

Re: ZX Printer Belt

They look great! Unfortunately my ZX Printer has got a cooked ULA and no replacement available :(
by McKlaud
Sat May 05, 2018 12:17 am
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 63
Views: 39432

Re: zx spectrum in zx81 case

I did not say that was anything wrong with the crystal. The type of the 7404 inverter is critical. You should try to install there 74HCU04 instead of either HCT or HC.
by McKlaud
Fri May 04, 2018 11:02 pm
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 63
Views: 39432

Re: zx spectrum in zx81 case

It works with 100ms RAM chips. I have them in my ZX Max 48K board. I think that in your case you are facing issues with the 14MHz clock, because the horizontal synchronisation is lost.
by McKlaud
Fri May 04, 2018 8:38 am
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 63
Views: 39432

Re: zx spectrum in zx81 case

What make of the inverter (7404) do you have? The clock signals generator works much better with HCU series instead of HC. Personally I would recommend Philips, NXP or Toshiba chip in this application. TI make 74HCU04 is not hassle free. I've tested a few of them.
by McKlaud
Mon Apr 30, 2018 6:06 am
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123687

Re: ZX81 ULA-in-a-CPLD

:D Andy, nice features :D