Search found 757 matches

by siggi
Thu Nov 23, 2017 7:44 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 25
Views: 356

Re: Help with Homemade ZX80-81- HIRES problem

Hi Siggi. Yes, probably during low refresh period the ROM add some data on data bus. I am planning to add some additional logic .. to disable the ROM or add some delay, during refresh period. (just to understand better the problem) Some idea about which signals needed to disable ROM in the right ti...
by siggi
Thu Nov 23, 2017 9:46 am
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 25
Views: 356

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano I don't understand, that ROM (or something similar) affects the behaviour of RAM. Maybe there is a collision between ROM and RAM due to an error in address decoding the RAM or ROM area? Then not the speed of the ROM, but the strenght of its databus output drivers would more or less affect...
by siggi
Wed Nov 22, 2017 6:02 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 25
Views: 356

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano the picture above is OK to generate /RAMCE: http://www.sinclairzxworld.com/download/file.php?id=4975 And to generate /OE you should use an AND gate: /RAMOE = /RS AND /RFSH (any of /RD or /RFSH LOW shall enable ram output and give a LOW at /RAMOE) About capacitors: you should have approx. ...
by siggi
Wed Nov 22, 2017 2:48 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 25
Views: 356

Re: Help with Homemade ZX80-81- HIRES problem

Hi Luciano you should use this logic as given above: This is from the ZXpand RAM select logic. RAM = true when RAM is required. assign IFRAMOE = !nRD | !nREFSH; assign IFRAMCE = (!nMREQ | !nREFSH) & RAM Could you show us a picture of your ZX81? Maybe there are other problems? Not enough deblocking c...
by siggi
Tue Nov 21, 2017 1:46 pm
Forum: Welcome Area
Topic: Pictures of Our Babies.
Replies: 14
Views: 332

Re: Pictures of Our Babies.

And here you can see, what Joachim uses his ZX81 for:

https://www.youtube.com/watch?v=-WudgMDa5kc

https://www.youtube.com/watch?v=2hIty9hYKfQ

:mrgreen:

Siggi
by siggi
Fri Nov 17, 2017 5:58 pm
Forum: Welcome Area
Topic: Pictures of Our Babies.
Replies: 14
Views: 332

Re: Pictures of Our Babies.

Here are some pictures of German babies ;)

http://forum.tlienhard.com/phpBB3/viewt ... ?f=2&t=300

Siggi
by siggi
Tue Nov 14, 2017 3:42 pm
Forum: Hardware
Topic: ZX81 cooling fan
Replies: 56
Views: 817

Re: ZX81 cooling fan

Actually the third pin should be used to control the speed of it. But I have no idea how... Maybe use a pic or arduino to set the speed, in relation to the internal heat. I leave it up to you which point you will measure. The downside of this again is that the pic has more processing power than the...
by siggi
Tue Nov 14, 2017 7:57 am
Forum: Hardware
Topic: ZX81 cooling fan
Replies: 56
Views: 817

Re: ZX81 cooling fan

Hi Moggy and others what do you think about that type of fan? https://www.ebay.de/itm/Notebook-Radial-Lufter-Radiallufter-Laptop-FAN-70mm-3-pol-Anschluss-5V-0-34A-NEU/322869248155?hash=item4b2c81c09b:g:pNUAAOSwZB9aAdCj So it would be possible to blow out the warm air through a slot at the left or ri...
by siggi
Mon Nov 13, 2017 3:28 pm
Forum: Hardware
Topic: ZX81 cooling fan
Replies: 56
Views: 817

Re: ZX81 cooling fan

Andy Rea wrote:
Mon Nov 13, 2017 3:04 pm
No no no your all wrong... you gotta go big :D

https://youtu.be/EM2G5vLGcQQ

:mrgreen: :mrgreen:
If those fans are used, all socketed ICs within the Zeddy would need a safety belt to remain in their socket :mrgreen:

Siggi
by siggi
Sat Nov 11, 2017 11:27 am
Forum: Hardware
Topic: ZX81 cooling fan
Replies: 56
Views: 817

Re: ZX81 cooling fan

I was wondering if it was possible to use it to draw warm air out of the case by placing it on the vents where the heat sink used to be. Hi Lardo cold air is heavier than warm air. Thus the warm air will leave the case at the highest possible hole in the case (MIC, EAR sockets?). Since the fan is l...