Microdigital TK 85 Teardown

Written By: Vinicius Rodrigues Bellini
Published: 20/05/23
  • Comments: 1

Microdigital TK 85 Teardown

Published: 20/05/23

Teardown

Introduction

The TK85 was a ZX81 clone made by Microdigital Eletrônica, a computer company located in Brazil.

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    • 9V DC = Nomo P2 power supply

    • Expansão = Expansion connector 2x23 edge pins.

    • Joystick = Joystick connector DIN-6-07M.

    • Mic = audio output for a datacorder.

    • Ear = Audio input for a datacorder.

    • Video = RF chanel 3 VHF output.

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    • Open it carefully because of the 2 keyboard flat cables.

    • Those flat cables are very problematic

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    • The upper part of the case is the keyboard, but the keyboard itself is not removable.

    • The lower part of the case is just a plastic part.

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    • The circuit board is a very compact circuit board with dual layer traks.

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    • MM2716Q-5 => 16Kb Eprom

    • 52164KSF/N => 64kb Rom ? It is a custom Microdigital Rom compatible with the NMC2764.

    • MCM4116BC-15 => 8 x 16,348 bits Ram = 16Kb Ram

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    • Just a RF Chanel 3 VHF modulator.

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    • Microprocessor

    • Rom

    • Eprom

    • Ram

    • Oscilator 555. Works as an PWM 5 Volt power supply to the micropocessor.

    • Spare space for an audio integrated circuit. It was never implemented in producion in this model.

    • Voltage regulator 7805

    • Frequency divider = 6,5Mhz used for video and 3,25Mhz used for actual clock.

    Olá Rodrigo, tudo bem?

    Tenho um TK 85 com 16 KB TB, e quero aumentar a memória pra 48 KB trocando as memórias 4116 por 4164.

    Mas encontrei três tipos dessa memoria, com terminações no nome, de -10, -12 e -15.

    Já viu fotos da placa original com 48K?

    Sabe qual a Microdigital usou?

    Pedro Jafet -

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Vinicius Rodrigues Bellini

Member since: 12/12/22

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