Microdigital TK 85 Teardown

ID: 161276

Description: The TK85 was a ZX81 clone made by Microdigital...

Steps:

1. 9V DC = Nomo P2 power supply
2. Expansão = Expansion connector 2x23 edge pins.
3. Joystick = Joystick connector DIN-6-07M.
4. Mic = audio output for a datacorder.
5. Ear = Audio input for a datacorder.
6. Video = RF chanel 3 VHF output.

7. Open it carefully because of the 2 keyboard flat cables.
8. Those flat cables are very problematic

9. The upper part of the case is the keyboard, but the keyboard itself is not removable.
10. The lower part of the case is just a plastic part.

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

12. MM2716Q-5 => 16Kb Eprom
13. 52164KSF/N => 64kb Rom ? It is a custom Microdigital Rom compatible with the NMC2764.
14. MCM4116BC-15 => 8 x 16,348 bits Ram = 16Kb Ram

15. Just a RF Chanel 3 VHF modulator.

16. Microprocessor
17. Rom
18. Eprom
19. Ram
20. Oscilator 555. Works as an PWM 5 Volt power supply to the micropocessor.
21. Spare space for an audio integrated circuit. It was never implemented in producion in this model.
22. Voltage regulator 7805
23. Frequency divider = 6,5Mhz used for video and 3,25Mhz used for actual clock.