Sinclair Spectrum Vega Plus Console

As part of Timex's introduction into the American market, they licensed the creation of ZX Spectrum compatible. The computer was named TS2068, launched in 1983, it was intended to be the high-end product of the line and, because competition with other brand computers was quite high at the time, they introduced several dramatic changes in the hardware that actually made the computer quite incompatible for anything that was not Sinclair BASIC. Nevertheless, some of the enhancements were  impressive.
Depending on the point of view of the user, all these changes in hardware ended being a really bad thing (most cases) or a really good thing (for just a few people with knowledge of electronics). It is quite hard for me to remain unbiased here as I am a very happy owner of a TS2068 and I do know something about electronics; I have a debt of honor with Sir Clive and the unknown individuals behind the developement of the TS2068 as this was the very computer that allowed me to polish the base knowledge of digital electronics which led me to become a proffesional in the field.

As mentioned above, the TS2068 came with several enhancements over the original Speccy, remember that this is 1983 so the Spectrum 128 was not yet available. Nevertheless, the TS2068 sported:

1) Enhanced Sinclair style keyboard, the keys were made of plastic, not rubber, pretty much like modern chiclet keyboards with a much better response and a larger spacebar right in the middle below the last line of regular keys. Not a proffesional modern keyboard but it was quite nice.

2) A cartridge slot with plastic cover placed on the right side of the case, which made the computer wider than the Speccy. This cartridge slot was used by a few commercial programs such as home accounting or spreadsheet applications. In most cases, the slot will be later used to house the Spectrum emulator cartridge.

3) An AY-3-8912 sound chip. Yes, the TS did come with the very same chip the Spectrum 128 will come with years later.

4) Two joystick ports, although these were not of the Sinclair of Kempston type so basically, useless unless the game loaded was designed for the TS2068 (altough the Timex joysticks were quite nice, used mercury activated reed switches instead of regular switches).

5) 24 KB of ROM (to handle the added hardware) and 48KB of RAM, totalling 72KB of memory. Obviously, the ROM was nothing similar to the Speccy's, this is the main reason less than 10% of the software written in machine code would actually run in the TS.

6} Video output connector.

7) Power switch.

In addition to the above, there were a few things not apparent/visible, without opening the case, that made the TS2068 a more sofisticated device than the Speccy:

1) The power supply delivered 15VDC instead of the Speccy's 9VDC, the internal 5VDC downstep regulation was achieved using a switching power supply instead of a 7805 like in the Spectrum and most computers of the time. This allowed for a much cooler operation so the TS2068 did not feature a heat sink as it generated very little heat.

2) The handling of the 72KB of memory was achived via bank switching, for that purpose, the TS2068 had a daughter board, placed inverted in the middle upper area of the PCB (I remember myself wondering what this little board was for, until I read the technical manual of the TS2068 and found out that it could actually address up to 16MB of memory, yeah 16MB via bank switching, a beauty).

3) An enhanced ULA supporting additional video modes. Besides the regular 256x192 of the Speccy, the TS2068 could do 256×192 pixels with colour resolution of 32×192 (two colors per character scan line) and monochrome 512×192(80 columns mode).
4) Much robust construction: despite a few design errors(evident by a couple of jumper cables on the PCB) one could tell right away that the TS2068 was designed to be of better quality than the ZX, thicker plastics, thicker PCB, better keys, etc.

Most of the enhancements made the machine very incompatible with the Speccy, which ultimately led to its demise. A couple of years later, when the machine was already discontinued a neat Spectrum Emulator cartridge appeared in the market, the cartridge basically eliminated the TS2068 ROM set and replaced it with a pure ZX Spectrum ROM, this made most Spectrum software runable with only a few exceptions. Before the Specrum Emulator cartridge, some people, like me, got a hold of the Speccy's ROM, burnt a 16KB EPROM with the code, mounted it on top the TS2068 main 16KB ROM and used a simple switch to enable one or the other.

The ZX ROM addition allowed Spectrum software to run but some of the H/W differences will pester the users for years:

1) The TS2068 ULA will output black color with brightness, so games featuring black backgrounds (or black sprites) will have an annoying grayish square in graphics if the programmers did not care of the state of the brighness bit in the attribute.

2) In the last years of the Speccy some programmers and software houses used extreme, borderlining programming tricks. Seriously affected by timing issues and differences in the I/O ports addressing could make some titles (like Arkanoid) to crash in the TS2068.

3) Although the sound chip was available, the ports used to address it were different than the ones on the Spectrum 128 so the sound would not work. Fortunatelly, most of these games could be corrected with a few pokes to work with sound in the TS2068.

4) The switching 5VDC regulation produced an annoying buzzing in some of the machines.

5) The clock for the TS2068 ran slightly slower than the ZX (3.528Mhz vs. 3.58Mhz), some games with extrict timing could have some effects totally off (I think Aquanoid was one of them, if I recall correctly).

6) The bus expansion connector did not follow the same order the ZX computers had, so most added devices will simply not work. A twister board connector could be made/purchased that will adapt most signals allowing the use of many Spectrum peripherals such as Interfaces 1 & 2, Kempston, etc. In order to have all signals (and eliminate extra signals) some of the tracks in the PCB had to be cut or rewired.

7) The tolerance levels of the cassette player input were quite low, cassette players with high outputs could easily blow a couple of components for the input circuitry in the ULA. Fortunately, placing an OP-Amp in the input with a couple of million amplification factor could cope with the problem, this also made the input much more reliable (it would load anything).

Despite of the differences with the ZX Spectrum which made the TS2068 not very suitable for gaming it was great machine, as I mentioned before, for the folks handy with a soldering iron and some knowledge of electronics the 2068 could be used as a solid platform for electronics projects. I'll describe below some of the addons I was able to put together despite of the limited knowledge of electronics I had a the time:

1) EPROM reader/programmer, this was just an adaptation of the same circuit used with the TS1000/1500.

2) 2KB RAM expansion, this 2KB mapped in a portion of the Spectrum ROM that was not used, a NMI will trigger execution so I used it as snapshop. Pretty much like the snapshot/dumper/poker interfaces of the time.

3) 5 1/4 floppy drive interface, I used the same RST 8 error handling the Sinclair Interface 1 used for microdrives, the only difference was the commands given to the disk drive.

4) 256KB memory expansion: the TS2068 used memory divided in banks and chunks, I couple of OUT instructions will switch banks as wanted. Based on this added feature I was able to have my own Speccy ROM modified to handle RAM banks. It would not switch banks automatically from BASIC but a non destructive reset (keep the contents of the RAM upon reset, like the C64 did) paired with an all electronics bank handler via NMI allowed me to have several different types of data in each bank; for example, a modified GENS assembler could read the text from a bank but compile and desposit the resulting machine code in yet another back. If the code got frozen or reset, a watchdog timer woudl produce an NMI that will reset the computer. Being not destructive the assembler could be reentered having the source text exactly as it was so I could correct and try again. Quite handy for debugging assembler programs, much faster than reloading from even the floppy disks.

5) Several automation boards to control knitting machines and ticker tape style LED displays, etc.

One of the most interesting things of the home computers was the fact that once the initial investment to purchase the computer it was not really necessary to drop more money unless one wanted someting extra like a joystick or a microdrive, etc. We actually were able to enjoy the computers for years without expending a dime, unlike the PCs were a gaming machine required a constant injection of capital into it if you want to play newer decent games.