Hi & Replica ZX80

[PokeMon]

Is very funny that nearly all 80ies computers have the same technical and optical keyboard layout with matrix 8x5, 40 keys arranged in the same positions, for ZX80, ZX81, Jupiter Ace, TK85.

[Wolf]

The TK85 was the equipment evolved over a line started by Microdigital with TK82, TK82 and TK83-C. Personal computers were small, ideal for beginners in computing, for home use, lightweight professional or educational and aficionados who wanted to learn computer without large investments. Was compatible hardware and software with English micro ZX81, Sinclair equipment.

Whole (CPU, memory, keyboard, etc) system is housed in a black plastic box 23.5 cm X 14.3 cm X 4 cm, weighing 500g. Uses an external power supply connected to the normal power grid. The feed stream (110 or 200 V AC) is converted to 10V DC.

The monitor program (operating system) and the BASIC interpreter are pre-recorded in a ROM 10Kbytes.

All electronic components are mounted TK85 on a single printed circuit board. On the back panel there are several connectors, three type "jack". The first (DC) serves to connect the power supply. The two remaining jacks (MIC and EAR), microphone and headphones, respectively, are used to connect the computer to an ordinary cassette recorder. Another is the coaxial type connector (video) and serves to connect the PC to the external antenna input of a conventional TV receiver. There are also a DIN type female socket for connection to a joystick and a special connector multiple contacts (expansion), providing access to all signals from the microprocessor (internal bus) can bind to a wide range of extensions and peripherals.

The TK85 cassette recorder used as auxiliary memory. The mechanical functions must be controlled manually, because the writer has no connection to the motor drive (REMOTE). It has two speeds read and write: normal, high and 300 baud, 4200 baud (which requires the use of recorders and tapes good quality low noise).

To load a program was to turn on the "EAR" the TK85 taking the headphone socket on the recorder. The recorder controls the volume was turned up to 3/4 of the maximum and the tone control was set at keenest possible.

The TK85 had as a joystick peripheral, cassette recorder, tone generator, allowing the recording of three channels of sound, printer (Printer TK) 32 column, speed of 45 cps and weighing only 300gr, used special thermal paper roll. Other peripherals and interfaces could be connected through the bus itself.

The software was made by the monitor program in extensive scientific BASIC interpreter, both recorded in ROM 10Kbytes. The BASIC commands had 46 and 37 mathematical and handling of characters, editing programs, etc chain functions. Programming in machine language was possible directly from BASIC, or assembler programs (Z80 Assembler).

There were large number of applications programs offered (recorded on tape) in the areas of entertainment and leisure, education, financial and administrative, professional, etc..

KEYBOARD

The keyboard is a QWERTY TK85, the embedded system and the box itself is simplified mechanical type, ie, small multifunctional furniture keys (rubber). The keyboard is quite compact, commanding up to 160 functions and characters with only 40 keys. This is accomplished by assigning various functions (up to five) to the same key. Switching between functions is accomplished by pressing the SHIFT, or GRAPHIC FUNCTION keys, or automatically, as it is typing.
An interesting feature of the TK85 and all those compatible with the ZX80, ZX81 and ZX-Spectrun, English, is that it is not necessary to type letter by letter the full name of commands, statements and functions of the BASIC language. When you press a key, the name of the associated instruction is transmitted by the extensive micro and screen. This mode of representation can also eacutém & considerable saving of time typing and prevents many errors in spelling and syntax, which makes a very appropriate micro TK85 for beginners.

VIDEO

The TK85 uses as screen a home TV unit in black and white or color (although the image is always monochrome), which is connected to the PC by a coaxial cable shield. The connection is made through the external antenna must be tuned to VHF channel 2. The sound is direct on TV fone.
The screen has 24 lines of 32 characters, uppercase only, black characters on white background, the characters can also be represented in reverse video (white on black background). The display resolution is 64 dots horizontally by 44 vertically.

Game puzzle TK 85 - 296KB

[gozzo]

The TK85 did NOT always have the sound generator fitted - mine hasn't - as I understand it, it was an 'upgrade/ 'optional extra'.... and the circuit and PCB has links for using either a set of 8 4116 RAMS (16K) or 8 4164's...whether using the 4164's actually gives you more RAM or not, I haven't yet studied the circuit diagram in detail yet, but some have said on various pages on the net that it does, as said above, go to 54K - mine has the 4116's ... ???!! Also in mine there are other parts 'not fitted' .. mainly around the cassette 'EAR' input circuitry, omitting the op-amp chip shown on the diagram... It would be great if 'replica' boards could be made of this machine, but no, I'm not desoldering mine and scanning it!

[Wolf]

The sound is out direct on TV in the TK-85.
I don´t have the diagram of the machine.
Initialy, I bought the TK-85 model with 16K RAM, and later, I exchange for another with 48K RAM.
Today he still being sold by a sales site (Mercado Livre) http://lista.mercadolivre.com.br/tk85-microdigital.

[gozzo]

The sound does not normally go out through the TV, there is a separate connector for it, unless yours has been 'modified', which is possible...... here is the circuit.... it shows the sound as going to a speaker, but actually goes to a socket next to the 9v input. Mine has the LM324 and sound circuits omitted...looks like they were never fitted from new... (apologies for the large picture size but if I reduce it, the quality will be worse if zooming into parts of it..)

[Wolf]

The normal Sinclair internal BASIC only access 16K, to access the remain 32K is necessary a series of Pokes or a little machine language routine.
The TK-85 don´t have speaker, the sound is direct out on TV speaker.
Only few commercial programs which access above 16K was disposable on local market, but there were several magazines that published programs using this extra space.
I have too a sound synthesizer, which as the 32K extra memory, is accessed by Pokes and ML.
Here is a example of a magazine of this time: http://www.google.com.br/url?sa=t&rct=j ... 0277,d.cWc

[gozzo]

Quite right, you can't use the above 32768 RAM easily, as with a ZX81, but I still say that a 'normal' TK85 does not output sound through the TV, mine wouldn't do, even if I fitted the sound chip circuit! , there are unused socket 'holes' on the PCB near the 9v DC in socket, and that connects to the output of a LM386 audio amp chip fed from the AY-3_8912.... do you have a picture of the insides of yours? Maybe its a rarer(?!) later version or has been 'upgraded' at some point?

[Wolf]

Ok, the sound is only a "click" which you can know you are tipping, with the synthesizer (bough apart) you can obtain a variety of sound.

[gozzo]

If you fit the AY sound chip and the rest of its circuitry, it gives the TK a built-in ZON-X81 compatible sound generator, so an external one is no longer needed...there was a webpage somewhere giving all the details...

[Wolf]

Interesting, this deserve an research and attention, thank you.