Search found 1257 matches

by mrtinb
Thu May 19, 2016 6:19 pm
Forum: Hardware
Topic: MIC amplifier
Replies: 71
Views: 14084

Re: MIC amplifier

you can try implementing the mic pre-amplifier I've built into my ZX81 clone, which is working well. http://forum.tlienhard.com/phpBB3/download/file.php?id=4639 If I try to input it into this simulator, the output is not much (240mV). Maybe I've set up the simulation wrong. http://www.falstad.com/c...
by mrtinb
Wed May 18, 2016 9:45 pm
Forum: Sinclair Misc
Topic: Help with resistors
Replies: 19
Views: 4816

Re: Help with resistors

I have some components I have difficulty identifying.

The components' texts are:

Code: Select all

+ ,1 35
4P7
4.00
UnknownComponents.jpg
UnknownComponents.jpg (63.45 KiB) Viewed 2481 times
by mrtinb
Wed May 18, 2016 9:37 am
Forum: Hardware
Topic: MIC amplifier
Replies: 71
Views: 14084

Re: MIC amplifier

PokeMon wrote:I think mrtinb is more looking for a solution working with original hardware without inside modifications. ;)
Yup :)
by mrtinb
Mon May 16, 2016 10:29 pm
Forum: Hardware
Topic: Creating Wilf Rigter's ZXKBD v3
Replies: 52
Views: 14259

Re: Creating Wilf Rigter's ZXKBD v3

It is finished!

https://youtu.be/ZpxC4x36jlg
image.jpg
(1.02 MiB) Downloaded 371 times
by mrtinb
Fri May 13, 2016 9:07 pm
Forum: Development
Topic: Creating TeleText?
Replies: 17
Views: 3893

Re: Creating TeleText?

dr beep wrote:How often could you 'refresh' the content of the page.

If frequently you can indeed use the settings of teletext as a screen and resolution.
This is not easy reading for me, but seems like a whole tele text screen can be fitted per frame.
by mrtinb
Fri May 13, 2016 1:43 pm
Forum: Development
Topic: Creating TeleText?
Replies: 17
Views: 3893

Re: Creating TeleText?

PokeMon wrote:Second a bit has a duration of 144ns vs. 154ns with the 6.5 MHz resonator in the ZX81. So I think you have to replace the resonator with a 7MHz type (gives 143ns pulses).
Err... the need of a change to the ZX81 almost beats the purpose.
by mrtinb
Fri May 13, 2016 1:01 pm
Forum: Development
Topic: Creating TeleText?
Replies: 17
Views: 3893

Creating TeleText?

Tele text is data sent between picture frames to a TV. Could a custom display routine on the ZX81 create Tele text data, and thereby let the Tele text decoder create the screen? Then the rest of the screen could be used in "FAST mode", because it is not shown on a Tele text decoder. And then the ZX8...
by mrtinb
Fri May 13, 2016 12:47 pm
Forum: Hardware
Topic: MIC amplifier
Replies: 71
Views: 14084

Re: MIC amplifier

Hi :) I'm trying to learn about transistors. Is there any map on the Internet which lists differences between these transistors (so I can see which might be replaced by others), so I would not have to read every single datasheet and make the mapping myself? BC107 BC108 BC109 BC546 BC547 BC548 BC549 ...
by mrtinb
Thu May 12, 2016 11:35 am
Forum: Hardware
Topic: Putting a ZX81 onto a CPLD
Replies: 59
Views: 12228

Re: Putting a ZX81 onto a CPLD

Hasn't this been done already?

http://www.bitcycle.org/retro/zx81/ula/
by mrtinb
Tue May 10, 2016 7:34 am
Forum: Hardware
Topic: Hi-res graphics mode in the ZX81
Replies: 13
Views: 6359

Re: Hi-res graphics mode in the ZX81

I meant:
1024MAK wrote:
mrtinb wrote:If I understand correctly - True Hires is either
  • a memory expansion with Hires capability,
  • a modified memory expansion, or
  • an internal modification addition of RAM circuits.