Author: Charles

Something for the Zeddy

The vLA81 has a few ‘hidden’ features which can only be fully unlocked with a 32K memory upgrade. If this is present then, as well as the standard 16K memory map, there are three other modes available.

They are all documented in the user manual but in summary they are:

RAM from 0x2000 (8192 dec) to 0x9FFF (40959 dec) – useful for HRG (high resolution graphics)

RAM from 0x4000 (16384 dec) to 0xBFFF (49151 dec) – the standard 32K expansion

RAM from 0x0000 to 0x7FFF (32767 dec) – a special mode which maps the ROM space to RAM

There have been several designs available to upgrade the ZX81 to 32K and I’ve always had the intention to provide a simple, inexpensive, design in kit form or fully built. I finally got around to it and here’s the result:

Couldn’t be simpler!

The design incorporates a thin PCB ‘shim’ between the 32K ram chip and the socket. The PCB does the simple job of rerouting a few pins to the right place and has no active components. Most of the ram chip’s existing pins are left intact. Four address wires are required to be connected to the ZX81 PCB as well as one short jumper under the board to connect A13 to the vLA81.

Available soon at all good vLA81 stockists 🙂

The vLA82 gets an upgrade

Ever wanted RGB quality video from a humble Speccy?

Getting decent a quality video output has always been a must have for most Speccy enthisiasts. From the simple composiste video mod to addons providing HDMI or VGA there is certainly quite a choice.

That’s where the upgraded vLA82 comes in. An RGB interface as well as an AY sound emulator have been shoe-horned into the original 40 pin DIP footprint to provide an upgrade that is simple to do as well cost effective compared to other options providing similar features.

The vLA82S+ (+ for RGB and S for AY sound) is installed in the existing ULA socket and connects to either an external (no Spectrum modification necessary) or an internal interface (replacing the RF modulator).

Units are now available on the vRetro Design online shop as well as occasionally on Sell My Retro.

Please see the vLA82S+ product page for more information.

Where to buy…

It has certainly been a challenging time for a micro business such as vRetro Design to try and navigate the various import rule changes in Europe and the UK over the past 9 months. We’re too small to justify directly selling to the EU due to the punitive compliance charges and handling VAT for the UK has added yet more work.

I have found no single solution so far and so, for customers, where you buy online will depend on your geographical location. vRetro Design now has an online shop which specifically caters for the EU and another which handles the rest of the world.

VAT collection at checkout, for those countries that require it, is now supported by both these shops leading to more transparency for import taxes and duty as well as a more hassle free import process.

If you’re in the EU then please visit : https://www.etsy.com/shop/vRetroDesign

Otherwise please visit :https://www.vretrodesign.com

I still sell on Tindie, but please be aware that VAT/GST is not collected at checkout (the main reason why I’ll be dropping Tindie soon) and further costs may be applied at the border.

vDriveQL Firmware Update 004 + MGG ROM support

Firmware release 004 is now available for the vDriveQL

This fixes a small problem with format. Also updated is the user manual which has instructions for troubleshooting the ‘vDrive not responding’ error.

At the request from a few of my German customers I’m providing a special build of the firmware to support the MGG ROM. This enables image formatting which was not supported when the MGG ROM was installed.

Please check out the downloads page for more information.

New Product: QL Power Converter

Been a while but have had a busy year. Amongst the odd projects that I’ve been working on is a power converter for the Sinclair QL. The original power supply is fairly hard to get and its unique power connector means that there hasn’t been an off the shelf alternative – until now.

QL_PSU_model
QL Power Converter

The converter takes a nominal 12V input from a customer supplied power supply (plug pack or other suitable power source with a 2.1mm DC plug) and converts this single voltage into the DC and AC voltages the QL requires. The converter comes with a custom 3D printed case and QL power plug.

Protection is provided with the converter returning to standby if excessive power draw is detected or if the external power supply is of insufficient power rating.

A user guide can be found here

If you want to grab one please check out my new store 🙂

Coming soon will be a similar product for the +2A/B and +3 Spectrum computers.

Enclosures for ZX and QL vDrives

Finally, an enclosure* to go with your vDriveQL or vDriveZX!

No need to dismantle an existing Microdrive for the case, you can now buy a custom 3D printed enclosure designed specifically for the vDriveQL or vDriveZX (there are two case styles to choose from).

Case includes a LED upgrade kit (rectangular LED + resistor). Please check out my new store for the case by itself or bundled with a vDrive and other options.

Acknowledgements: Michele Perini for the original 3D case model

*Note the enclosure is 3D printed and although the visible surface finish has been optimized there are still some minor surface imperfections due to the printing process.

Installation instructions for the QL case can be found here,  and for the ZX case here

vLA News-updated

The complete vLA family (so far)

vLA81/82/128 now all available on SellMyRetro….

After the vLA1 was completed I set myself a challenge to replicate the functionality of some of the other Sinclair ULAs, firstly the ZX81 followed by the ZX Spectrum and finishing with the Toastrack ULA (as this would leverage most of the ZX Spectrum ULA design).

I knew that all of these had been already done before but as the inner workings had not been published in detail this meant that there would be plenty of design still required (the part I enjoy the most). Armed with Grant Searle’s fantastic ZX80/81 repository and Chris Smith’s wonderful expose of the Spectrum ULA, I started about a year ago on the vLA81.

A functioning vLA81 was completed in October 2018 and work started on the vLA82, by far the most complex of the three. A working vLA82 prototype was completed in March 2019 and work was begun on the vLA128. In parallel with the design, schematics were refined, PCBs finalised, and samples sent out for testing when they became available.

A working vLA128 was completed in May 2019. Over the time the other vLAs were progressing the vLA81 underwent its own evolution. As the Xilinx XC9572XL CPLD used in the vLA81 had unused resources I decided to add some extra functionality (see features below).

The complete vLA family (so far):

vLAx4

Feature summary:

vLA81
1. Fits within the same 40 pin DIL socket outline as the original ULA.
2. Narrow IC pins for easy plugin ULA replacement. In most cases the existing socket will be OK.
3. Provides the same functionality as the 2C210E Sinclair ULA.
4. Video level selectable between standard video (suitable for direct connection to a 75 ohm monitor input) and high sync level (suitable for the modulator input or some video mod boards).
5. Back porch on/off select.
6. Internal 32K memory support (High or Low for the different hires schemes).
7. Programmable user configuration gives access to:

  • Inverse or normal video and choice of black or white border.
  • 50/60 Hz video standard.
  • Ability to map ram to the ROM space (write protect enable/disable – 32K internal ram required).

8. Configuration port socket provided on PCB base for external config switch option.
9. Tested with an extensive suite of ZX81 software (full list to follow).
10. Ideal for preserving the original ZX81 ULA.
11. Low power consumption.

vla81_top
vLA81 installed in an issue one ZX81

vLA82
1. Plugin ULA replacement. In most cases the existing socket will be OK.
2. A low profile and 40 pin DIL footprint means that the vLA82 is designed to fit in a ‘rubber key’ ZX Spectrum case without further modifications.
3. Provides the same functionality as the 6C001-7 Sinclair ULA.
4. Passes standard ULA benchmark tests (floatspy, Brendan’s Diagnostic ROM etc.).
5. Tested with an extensive suite of ZX Spectrum software (full list to follow).
7. Ideal for installing in an aftermarket Spectrum PCB without needing an original ULA.
6. Low power consumption.

vLA82_top
vLA82 installed in an issue 4S Spectrum

vLA128
1. Fits within the same 48 pin socket outline as the original ULA.
2. Narrow IC pins for easy plugin ULA replacement.In most cases the existing socket will be OK.
3. Provides the same functionality as the Sinclair 7K010E-5/ Amstrad 40056.
4. Passes standard ULA benchmark tests (floatspy, Brendan’s Diagnostic ROM etc.).
5. Tested with an extensive suite of Spectrum 128/+2 (Grey) software (full list to follow).
7. Ideal for preserving the original Toastrack/+2 ULA.
6. Low power consumption.

vLA128_top
vLA128 installed in a Toastrack (will also work fine in a Spectrum +2 Grey)

 

If any of these items would be of interest then please email to vdrivezx@gmail.com