Big box of PCB’s

January 30, 2020

This week saw the arrival of another big box of PCB’s. A lot of PCB’s. Some old but many new.

Arriving where some new stock of RC2014 prototype board, prototype plus boards and extender boards which I sell on Tindie.

Also in the box where some new board designs. No new RC2014 PCB’s this time but some boards for the ZX Spectrum and Commodore 64 computers. I’ll share more details of these in the coming days and weeks.

Time to break out the soldering iron 🙂

Here’s my Tindies store.


ZX Spectrum Projects – Data Storage

December 31, 2019

When the ZX Spectrum came out in 1982 the options for data storage on home computers were very limited. You usually had the choice of audio cassette tape or floppy disk. The ZX Spectrum initially came with audio cassette storage via an external cassette player/recorder. Sinclair Research would develop a variation of tape storage in their microdrive system via their Interface 1 add-on and it was only very much later that floppy disk storage would appear as a add-on option (i.e. DISCiPLE drive) or as a official computer model (the ZX Spectrum +3)

Now, lets fast forward to the present. Audio tape cassettes and floppy disks are very much a thing of the past and getting new blank tapes or disks is difficult to almost impossible.

However all is not lost as the retro community has been very busy in the intervening years and has come up with many alternatives to tape and disk storage. These alternatives are usually based on either Compact Flash or SD-Card. Below is a short list of some DIY projects:

“Everdrive”/DivMMC for Spectrum list
View at Medium.com

SD-Card interface round-up
http://www.retroisle.com/general/sdcard_roundup.php

ZXMMC+ (sd-card access, IF-1 – RS-232 and Network), 1MB ram/rom, Kempston joystick
http://www.probosci.de/zxbada/zxmmcp/index.html

ZXcard DIY SD/MMC interface

ZXcard DIY SD/MMC interface


https://easyeda.com/sundbyk/ZXcard_II-234ad2c853054ed68d318ca9ed6dcd9f

maxduino – Unified firmware for tzxduino and casduino
https://github.com/rcmolina/MaxDuino_v1.53

TZXDuino
http://arduitape.blogspot.com/

TZXDuino-Uploader
https://github.com/rickyelqasem/TZXDuino-Uploader

Tapuino-Reloaded – A reworked smd version of the Tapuino Mini Pro.
https://github.com/arananet/Tapuino-Reloaded

TzxDuino-Reloaded – A reloaded version of the TzxDuino
https://github.com/arananet/TzxDuino-Reloaded

TZXDuino Arduino based TZX
https://github.com/StormTrooper/TZXDuino


ZX Spectrum Projects – Diagnostic & Repair

November 1, 2019

Now I’m back on my retro computers I’ve put together this quick guide for those looking to diagnose and repair ZX Spectrum computers.

Schematics and Service Manuals:

Having a set of schematics or even better a full service manual is the good thing to have before starting any repair. Fortunately for us, full schematics and service manuals for the all ZX Spectrum models are available on the web. I have my Speccy schematics printed out on the biggest paper size I’ve got access to, namely A3. The service manuals are a great place to start when looking to diagnose a fault.

Schematics and Service manuals can be found at:

World of Spectrum

Spectrum for Everyone

IC Data sheets

wikipedia
7400 series
4000 series
Zilog Z80

Diagnostic Software Tools:

Happily the ZX Spectrum has quite a few diagnostic software tools to help the would be fixer in his fault diagnostics. Most of these are based on external ROM device which avoids the need to have a fully working Speccy or the problem of loading diagnostic software from tape.

Here’s a few ROM based diagnostic tools

Brendan Alford on github has “ZX Diagnostic”

Paul Farrow of fruitcake has the following ROM tools: 128K RAM Tester & ROM Tester
he also has the official Sinclair Test ROM as well
Phil Ruston of Retroleum has the following “ZX Spectrum Diagnostic ROM”

Tools needed:

Hand tools
Side cutters
Pliers
Screw Drivers: Philips and flat blade
IC extraction tool

Soldering Iron
De-soldering tool

Multimeter

Advanced
Oscilloscope
Power Supply (Adjustable/current limited)

Diagnostic software tools (see above)

TV Monitor/Screen (or car reversing monitor for composite video)

Repair mat
Anti static wrist or foot strap
IPA Wipes (no not the beer) – Isopropyl alcohol to clean edge connectors and contacts

Good web sites:

If the your own best efforts have not yet found the problem then there several good web sites that share their repair achievements where you can search. I like the following sites:

Dave Currah of Tynemouth Software

nightfallcrew

If you’re still no wiser, then try asking on one of the various Retro Computing Forums or general electronic forums in their repair section if they have one.

Remember to share as much information about the Speccy model, what it is not doing and what you have tried so far. Avoid simple statements like “Speccy not working please help”. It goes without saying that following the forums etiquette for posting will usually get you a more productive and polite response.

World of Spectrum forums
https://www.worldofspectrum.org/forums/

These are more general forums:
atariage forums

EEV Blog fourms


ZX Spectrum Projects – HD Video output

October 28, 2019

I’ve neglected my retro computer collection for a while now, so recently I’ve been dusting off my collection, starting with the ZX Spectrum to start some new projects with them. Whilst I have a few that need repairing I quickly got distracted into wanting to make a cool project for them.

Getting the Speccy to work with modern TV’s is becoming more of a problem. I’ve made composite video modifications to my Speccys in the past, I even made a small PCB that fits into space where the existing video modulator sits. But I want to see if HD / High Definition video was possible. By HD video I mean either VGA, DVI, DisplayPort or HDMI.

A quick web search found me Victor Trucco’s TK Pie. This is an interesting way of using a Raspberry Pi Zero to provide a High Definition (HDMI) video interface to the Speccy. It uses a mix of external hardware (CPLD) and the processing power of a Raspberry Pi Zero to capture writes to the Speccy’s video RAM and convert the pixel data into HD video via the Pi’s HDMI. There’s a similar project for the BBC Micro called RGDtoHDMI.

Here’s a link Victor’s web site and TK-Pie source code files

There are couple of useful reviews of TK Pie by GozdniJezek, Building TK-Pie by Victor Trucco

and martin@8bity, HDMI output for Sinclair ZX Spectrum – TK-Pie

Some more searching found me the next two devices. They don’t seem to be DIY projects but I thought they looked interesting.
Ben Versteeg at ByteDelight has ZX-HD: The story of the ZX-HD

and also Goran Radan with his ZX-VGA-JOY