Search found 5044 matches

by 1024MAK
Sun Feb 25, 2024 10:47 pm
Forum: Welcome Area
Topic: Hello from Poulette73
Replies: 9
Views: 384

Re: Hello from Poulette73

Issue one board
Issue one board
Issue one board
Issue 3 board
Issue 3 board
Issue 3 board
Click on the pictures for the full size version.

Pin 16 shown. An alternative is on the connection for diode D9 indicated.

Mark
by 1024MAK
Sun Feb 25, 2024 5:26 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

msknight wrote: Sun Feb 25, 2024 5:01 pm This is messy, but it's "open" so you can see what I've done. - probably something stupid, knowing me.
I think I will need to open those pics on a PC rather than my 'phone while crawling around in the loft :lol:

Mark
by 1024MAK
Sun Feb 25, 2024 5:23 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

msknight wrote: Sun Feb 25, 2024 4:49 pm I have some N4007 - should I use those instead?
No. They are designed for low frequency use.

Mark
by 1024MAK
Sun Feb 25, 2024 4:41 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

Not having a RAM pack in front of me, I can't answer your question directly. Both the black band on both diodes on both diodes indicates the cathode, and should be connected to the circuit that goes to the relevant edge-connector socket pins. The other end of each diode should form a connection with...
by 1024MAK
Sun Feb 25, 2024 3:20 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

In both the simulations, click the H inputs to flip each one to L in turn, and observe the output, both the logic level and the voltage.

Mark
by 1024MAK
Sun Feb 25, 2024 3:10 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

Simulation of the added circuit using 1N4148 diodes:

Link

Same circuit, but using Schottky diodes:

Link

Mark
by 1024MAK
Sun Feb 25, 2024 2:44 pm
Forum: Hardware
Topic: 16k Sinclair issue 1 pack
Replies: 28
Views: 516

Re: 16k Sinclair issue 1 pack

Well, if no one has any ideas to help on this... Which diodes did you use in the end? Standard silicon diodes have a forward voltage of between 0.55V and 0.7V at low currents. Germanium have a much lower forward voltage, but are rather hard to find now. Hence why I recommended Schottky diodes (BAT ...
by 1024MAK
Sun Feb 25, 2024 11:15 am
Forum: ZX BASIC
Topic: New Screen Saver :-) Enjoy!
Replies: 3
Views: 245

Re: New Screen Saver :-) Enjoy!

Here's my screensaver:
IMG_7867.jpeg
Runs on a 1K machine.

Mark
by 1024MAK
Sun Feb 25, 2024 9:31 am
Forum: Hardware
Topic: How close is the ZX80/81, Jupiter Ace and Spectrum in machine code backwards hardware compatibility?
Replies: 5
Views: 111

Re: How close is the ZX80/81, Jupiter Ace and Spectrum in machine code backwards hardware compatibility?

Memory Maps compared ZX80 / ZX81 0000-1FFF ROM (8K bytes for ZX81, 4K bytes for ZX80 2000-3FFF Echo of the ROM 4000-7FFF RAM (1K or 16K bytes) 8000-BFFF Echo of the ROM C000-FFFF Echo of the RAM, used for generating the display Spectrum 16K/48K/Spectrum+ Memory Map 0000-3FFF ROM (BASIC) 4000-7FFF R...
by 1024MAK
Sun Feb 25, 2024 9:07 am
Forum: Hardware
Topic: How close is the ZX80/81, Jupiter Ace and Spectrum in machine code backwards hardware compatibility?
Replies: 5
Views: 111

Re: How close is the ZX80/81, Jupiter Ace and Spectrum in machine code backwards hardware compatibility?

Hi, I'm curious in how backwards compatible programming in machine code, is between hardware in the ZX80, ZX81, Jupiter Ace and Spectrum? Not very is the generic answer. Let's take the ZX80 and ZX81 first, If you are careful, the same program can run on both of these. However, the tape format is di...