Retro: ZX Spectrum Hardware Mods ‘n’ DivMMC Enjoy!

May 20th, 2014 by Mr.Mouse

Here’s a small blog on prepping your old 8-bit ZX hardware to do some retrogaming: on fixing keyboard membranes, creating a composite video signal and using the DivMMC Enjoy! cartridge to ease your storage life. 

But before that first a word on Internet sellers of second hand Sinclair computers. You should be aware that a reknown problem of the ZX keyboards is that the membranes die in the course of 20 years. If you happen to stumble upon a ZX being sold on the internet, always ask them to check the keyboard. I’ve bought three computers the past few weeks, and ALL of them had worn keyboard membranes. But only one seller reported this before finishing the deal! The other’s claimed “it worked before I shipped it!”. Yeah right. Not in a million years, buster! However, I fixed them like this:

At www.sellmyretro.com you’ll find all kinds of retro sellers, with old but also new hardware for the aging computers. Among those is Rich Mellor of http://www.rwapsoftware.co.uk/ that manufactures brand new keyboard membranes for different platforms. Check photograph 1 and 2 below. You’ll see the worn membrane of a 16K ZX Spectrum I bought, most clearly visible in picture 2 where the conductive stripes to relay the keyboard presses have gone totally black and fail their function completely.

After that it is quite simple to repair the keyboard. Open it up, replace the membrane and close it again. You can see how I did it for one of my ZX Spectrum + in the pictures below. Picture 4 shows the old membrane, picture 5 the new one.


Composite video

Back in 1986 there was an article in Crash about a hardware mod to output composite video instead of an RF signal (antenna). This trick was based on the fact that the computer generates composite video, but feeds that to the RF modulator to transform that into a RF signal out. By leading this composite video signal to the RF socket, effectively bypassing the RF modulator, you’ll have a cristal clear image. Simply attach an AV jack to the RF socket and a monitor (like the Commodore 1084s) or a HD TV with AV-in. Though I’m no good at soldering, this mod even I could do as you can see in the before and after pictures 7 and 8.

The arrow indicates the composite signal bypassing the RF modulator (the square thingy). Three other leads were disconnected for this to be succesful. If you look carefully you might see which.

DivMMC Enjoy!

Finally, the DivMMC Enjoy! created by Ben Versteeg from Eindhoven, The Netherlands. Check here for his old website and here for his new one. The DivMMC Enjoy! is the successor of the widespread DivIDE. DivIDE is an interface between your Spectrum and all kinds of mass storage devices, such as your PC hard drive, CD-ROM drive and Compact Flash card. The Enjoy! is the affordable alternative that enables you to store your software on an SD card to be inserted in the interface. Upon purchase you will get the interface without a case, as Ben is still working on that using 3D printing. You do get a 4 Gb SD card, with all necessary software preinstalled, besides some demos and games. The firmware for the interface is namely ESXDOS by Papaya Dezign. This is preinstalled on the EEPROM of the Enjoy! (flash memory) and can be manually updated. The Enjoy! has a joystick port to connect standard joysticks that works like a Kempston joystick interface, which was supported in many games. There’s also a RESET button and an NMI button. The NMI button is used to start the menu and browse the SD card and start *.TAP software for instance. TAP is a tape emulation format. However, that is not the only thing the DivMMC Enjoy! can handle and the manual can provide more information, like details about the extended BASIC commands to operate the interface. A handy feature is also the option to freeze a game at any time, store a snapshot and continue later. If you’re feeling particularly bold you could delve into the ROM code using the JTAG pins. The DivMMC Enjoy! is an excellent interface to get fast access to gigabytes of games and other software. World of Spectrum is a great starting point if you’re looking for games and tools! Check the pictures below to see the interface plugged into my Plus.  View Ben’s promo vid to see it in action!

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