Our PEEK*a Member subject for this month took us to the home of Wes Brzozowski, an electrical engineer by occupation, had long been interested in computers, particularly ones using the Z80 microproccessor chip. Having even toyed with the idea of building his own computer using the Z80, Wes jumped at the chance to buy the kit for the Sinclair ZX-81. He reasoned that the ZX-81 kit gave him “an inexpensive way to have a Z80 type computer that” he “could hang more junk on.” Being a “tinkerer”, Wes wanted to improve on the Sinclair. In fact, even today Wes says that he spends too much time trying to make it into a better computer than he does using the better computer he already has!
Assembly presented few problems. Wes did have some pins break through the tape and contact the ground strip, but the biggest problem he had was lack of sleep! Once the kit arrived he could not put it down and worked well into the night. He then took a vacation day the next day to correct the problems and fire up the ZX-81! He is probably not the only one to have done this. Later his father would buy a kit and send it to Wes for assembly.
After about six months of working within the limits of 1K, Wes saw the virtues of the 16K-RAM pack while visting his father out west. He does not regret the time spent without a 16K RAM, however, he felt it helped him learn the disciplines of compact programming plus learn just how the ZX-81 memory is organized. One early project was to disassemble the ROM by hand. (This does not mean take it apart, it means checking every address of the ROM). The ROM is 8K, that is 8 times 1024 bytes, and that is when Wes found out “that 8K is a very big number!” He never completed the project by hand, but he learned a lot
He is set up on a bookcase in a study and the first thing that you notice is the “volt meter” next to an array of connections at the rear connector. It is not a voltmeter, but rather a fourth generation Brzozowski Box for Computer Cassette Compatibility, hereafter referred to as the “Black Box. This is the fourth and most sophisticated unit he has built to monitor the load/save procedure as well as let him hear the signal, get a reading on the meter, plus “clean up” signals of poor quality cassettes to insure loading. The “Box” is very professional and expensive looking-with neatly labelled knobs and switches. Wes says the “Box” has maybe $40 worth of materials and that he did spend nearly as much time on the case as he did wiring up the inside.
Additionally, Wes has built a keyboard that plugs into the rear edge connector. Wes wants to avoid wiring into the computer itself as these wires inevitably will come loose due to moving the computer around. That doesn’t mean he hasn’t opened his ZX-81 up once he had it built. Far from it-he couldn’t get another wire inside the computer without using a shoe horn. Other “junk” he has added include a reset system-the “Box” has the ON/OFF switch-hardware to produce 64 characters (which he has used to produce lower case letters!)-even a switch that turns off the repeat key (even though he hasn’t built the keyboard with a repeat key on it!).
He also has a collection of Sinclair reject RAM packs that he got at a ridiculous price. Five of them were easily repaired. The most interesting one is the one with the “chirping oscillator”.
Software selections include utilitarian things like “Tool Kit”, “Assembler”, “Disassembler”, and “Hot Z”. He also has some games.
Wes has just purchased a TIMEX 2040 printer and he likes it very much, using it primarily for program listings. He particularly prefers the paper of the TIMEX over that used on the Sinclair version.
Several software projects warrant mentioning. First, it seems Wes and his family enjoy another pasttime-launching homemade rockets! So Wes developed a program that computes the altitude the rocket will achieve given such variables as launchsite altitude, temperature, the thrust of the engine, weight and etc. He says it allows him to pick an engine size that will give him a good launch but avoid losing the rocket in the clouds!
Though the hour was too late to demonstrate it, Wes told me how he uses a “choo choo” train to help teach his small daughter the letters of the alphabet. The train moves across the screen and stops at a letter. When the child presses the key with that letter, I understand a smiling face rewards them and the train moves to another letter.
Several programs were developed because Wes wanted to find out how to beat the system i.e. copy programs that could not be copied. Also, because of his programming work is usually machine code, he is concerned that he does not “drop a bit” in loading/saving. So he has two “Checksum” programs – one of which can just go at the head of each BASIC program and is invisible – that is the program comes up running unless the checksum is wrong then you get a load check failed prompt. Wes also demonstrated a unique program that listens to a loading program in, I believe,64 byte groups and plots a bar graph of the sound. By turning the volume up or down you can determine the most desirable volume setting. It is a fascinating idea!
Wes Brzozowski is an extremely well organized computer hobbyist. An expert on circuit design in electrical engineering he combines the engineering knowledge with strong communicative skills and the patience of a saint. I gained much insight into the hardware that can be “hung on the Sinclair” by “tinkerers” like Wes. In fact, I trusted him to open my TIMEX/Sinclair up and drill more ventilation holes. Thank you Wes for that assistance.
But Wes’ strong suit is his enthusiasm for the Z80, the Sinclair, and the hobby. If you saw his first presentation at the June meeting on machine code, you saw that enthusiasm and communications skills. I mean Wes made “twos compliment” sound exciting!
He concluded our interview with the observation that the Z80 is a slick microprocessor and the Sinclair is a marvellous toy for the price. I learned a great deal in our several hours at his home and appreciate the chance to have visited him.