Feb 19
For the past few days I’ve been trying to get the DC-DC circuit working on a ZX Spectrum Issue 3. The problem was TR4 kept drawing too much current which damaged the transistor. The DC-DC circuit is really a horrible design. Even after applying the DC-DC mod which makes the circuit more stable I still …
Dec 09
After buying a few faulty ZX Spectrums on eBay which were having memory issues I decided to build a diagnostic cartridge to help troubleshoot the RAM issues. After looking through various internet sites I eventually found a schematic and diagnostic ROM by Dylan Smith. The original site however is no longer online but I did …
Aug 18
To load programs on the AZ Spectrum you need a cassette player…or so I thought. Came across TZXDuino which lets you play files from the SD card using an Arduino and a amplifier. Rigged this up in a morning and it works beautifully. I updated the code to use a LCD 16×2 without I2C. …
Aug 12
Not having a programmer for this chip I decided to use my Arduino. After trying out various projects on the internet I eventually came across TommyPROM which uses 74LS164 serial to parallel shift registers. Wired up to my Arduino Uno, fired up TerraTerm and uploaded the diagnostic ROM to the 28C256. The 28C256 is a reflashable …
Aug 10
After looking on the internet there seems to be a lot of confusing information on the pinouts for building a DIN to SCART cable. I’ve looked through the harlequin schematic and SCART pinouts and it should be as follows: Spectrum Harlequin RGB DIN to SCART DIN ———–> SCART PIN – SCART Function Pin 1 ———–> …
May 24
After spending a good few hours reading up on retro computers and wanting to relive my childhood I’ve decided to give the ZX Spectrum Harlequin a go. Yes, I know its probably cheaper to buy a complete assembled board or even a ZX Spectrum from eBay, but where is the fun in that! There are many …
Recent Comments