Search found 2469 matches

by 1024MAK
Sat Sep 07, 2019 1:56 pm
Forum: Hardware
Topic: ZX80 trouble shooting
Replies: 37
Views: 1720

Re: ZX80 trouble shooting

Hi Moggy So just to be clear, the only chips you changed were the Z80 and the ROM/EPROM chips, yes? The symptoms are a white screen only (no inverse K) and the +5V supply is present and correct on all chips. So my questions so far are (and forgive me if I start with the obvious things that you may h...
by 1024MAK
Fri Sep 06, 2019 2:22 pm
Forum: Hardware
Topic: ZX80 trouble shooting
Replies: 37
Views: 1720

Re: ZX80 trouble shooting

Lardo Boffin wrote:
Fri Sep 06, 2019 1:04 pm
Where do I get the 5 and 9V rails on an 80? I’m not familiar with the layout of these.
7805 regulator pins or edge-connector pins are the easiest places.
Apart from lacking the ROMCS line, the edge-connector pin outs are the same,

Mark
by 1024MAK
Fri Sep 06, 2019 10:48 am
Forum: Hardware
Topic: ZX80 trouble shooting
Replies: 37
Views: 1720

Re: ZX80 trouble shooting

The Sinclair 16K RAM pack is I believe, one type that should work. What voltages do you get on the +9V and +5V rails with the ZX80 running on its own, and then with the RAM pack attached? It is possible to use an EPROM, but pin compatible EPROMs that are suitable are a lot less common compared to th...
by 1024MAK
Fri Sep 06, 2019 2:41 am
Forum: Welcome Area
Topic: Hello fellow 8 bit owners
Replies: 3
Views: 513

Re: Hello fellow 8 bit owners

Welcome on board Andy!

:D :D :D

Hello. A warm welcome to Sinclair ZX World.

I hope you have fun here :D

I don’t have an original Ace, but I do have a recreated ACE. If you can find the relevant thread, there should be some photos :mrgreen:

Mark
by 1024MAK
Fri Sep 06, 2019 2:34 am
Forum: Hardware
Topic: ZX80 trouble shooting
Replies: 37
Views: 1720

Re: ZX80 trouble shooting

Hi Which RAM pack did you try? Not all are necessarily completely compatible with a ZX80... Sir Morris did a special version of the ZXpand for the ZX80, but I can’t remember what the differences are. But do keep in mind that the ZXpand has an overlay ROM included. The overlay ROM has to be based on ...
by 1024MAK
Tue Sep 03, 2019 1:54 pm
Forum: Hardware
Topic: I released my ZX81+35 ZX-81 clone design files on Github
Replies: 17
Views: 1252

Re: I released my ZX81+35 ZX-81 clone design files on Github

1E2CE72C-A55D-431E-BCCE-C56CDAD6C67C.jpeg
ZX81 keyboard connector pin-out
Mark
by 1024MAK
Tue Sep 03, 2019 1:40 am
Forum: Hardware
Topic: I released my ZX81+35 ZX-81 clone design files on Github
Replies: 17
Views: 1252

Re: I released my ZX81+35 ZX-81 clone design files on Github

This is the schematic that I mostly use (apart from the French video circuitry):
Image

Although to be fair, I don’t remember doing any detailed checking of the keyboard matrix...

Mark
by 1024MAK
Tue Sep 03, 2019 12:30 am
Forum: Hardware
Topic: I released my ZX81+35 ZX-81 clone design files on Github
Replies: 17
Views: 1252

Re: I released my ZX81+35 ZX-81 clone design files on Github

Yes, although the ZX Spectrum matrix looks the same as a ZX81 matrix, they are different.

It helps if you draw it out on paper...

Mark
by 1024MAK
Fri Aug 30, 2019 10:16 pm
Forum: Hardware
Topic: Improving Timex/Sinclair Tape Loading
Replies: 149
Views: 28992

Re: Improving Timex/Sinclair Tape Loading

Sorry, the delay is 100% my fault :oops: . Far too many distractions coupled with rather a lot going on with my work life.

I’ll go poke myself with a ULA hot soldering iron :shock:

Mark
by 1024MAK
Thu Aug 29, 2019 11:49 am
Forum: FAQs
Topic: why only 1k of ram?
Replies: 2
Views: 951

Re: why only 1k of ram?

Sinclair’s aim with the ZX80, was to produce the lowest cost, but fully functional home computer that was possible. Hence every single part of the design and manufacturing was geared towards this. Apart from the Z80, the ROM chip and the RAM chips, all the remaining chips were inexpensive standard 7...