Search found 120 matches

by McKlaud
Fri May 04, 2018 11:02 pm
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 63
Views: 5069

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: 5069

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: 168
Views: 14064

Re: ZX81 ULA-in-a-CPLD

:D Andy, nice features :D
by McKlaud
Thu Apr 19, 2018 10:55 am
Forum: Welcome Area
Topic: Hello from Canada
Replies: 15
Views: 934

Re: Hello from Canada

Any unregulated PSU gives you more voltage than its rated voltage if the load is lower that the nominal load. Make the story shorty, it is uncommon that the ZX81 PSU gives approx. 10.5V when connected to the ZX81. In idle (no load connected) the PSU output voltage can reach 14.5V easily. Bear in min...
by McKlaud
Mon Apr 16, 2018 7:41 am
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 168
Views: 14064

Re: ZX81 ULA-in-a-CPLD

Nice and good to hear from you that you made some progress. My unit is in a storage box waiting till I will be back home in a few weeks.

BTW do you have the barebone 32K RAM on your testing PCB?
by McKlaud
Mon Apr 16, 2018 7:30 am
Forum: Hardware
Topic: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity
Replies: 10
Views: 619

Re: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity

Have a look and measure a supplying voltage to TEA200 chip. The PAL encoder requires 12V supply (pin 11 on it).
by McKlaud
Mon Apr 16, 2018 7:24 am
Forum: Welcome Area
Topic: Hello from Canada
Replies: 15
Views: 934

Re: Hello from Canada

On the output should be +5V +/- 0.25V. Anything above +5.25V means that something is wrong the voltage regulator chip. Take it out and measure a resistance between GND (middle soldering point of this chip) and +5V rail (right soldering point). The reading should be in low kiloohms but definitely mor...
by McKlaud
Sun Apr 15, 2018 7:13 pm
Forum: Welcome Area
Topic: Hello from Canada
Replies: 15
Views: 934

Re: Hello from Canada

Hi Ogien, Good that you joined us on here. I have attached a picture of the 1st broken RAM pack (48K) There is one IC on there that gets very hot quickly on it which I circled. Not sure if that is the problem but in my limited experience very hot ICs are usually not good. This pointed IC is a voltag...
by McKlaud
Fri Apr 13, 2018 9:13 pm
Forum: Development
Topic: New game - BiggOil
Replies: 4
Views: 446

Re: New game - BiggOil

Well done! I enjoy it and it is addictive. :)

Some annoying flickering when I unroll the pipe horizontally. I run the game under the ZXSP Emulator.