ZX81 Parts List |
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Semiconductors |
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| IC1 | Ferranti ULA, Sinclair Computer Logic. Obsolete part. | |
| IC2 | 2364 | ZX81 BASIC ROM |
| IC3 | Z80A | Processor |
| IC4 | 4118 | 1Kx8 NMOS RAM. Obsolete. Alternatively 6116 (2Kx8) CMOS RAM is bigger and uses less power. |
| IC4a,b | 2114 | 1Kx4 NMOS RAM, the usual configuration. |
| D1-8 | General small signal silicon IN4148, but germanium or
Schottky diodes preferred- they have < 0V6 voltage drop. |
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| REG | 7805 | 5V 1A regulator. Requires a heatsink. |
Resistors |
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| R1 | 10K | |
| R2 | 680R | Impedance between ULA RAMCS and RAM /CS |
| R3 | Not used | |
| R4 | 18k | |
| R5 | 330R | |
| R6 | 2K2 | |
| R7-14 | 470R | |
| R15 | 220K | |
| R16 | 1K | /BUSRQ pull-up |
| R17,27 | 1K | |
| R18-26 | 1K | Impedance between Z80 A0-8 and ULA/ROM A0-8' |
| R28 | 680R | Impedance between ULA ROMCS and ROM /CS |
| R29 | 1M | |
| R30 | 0R | USA only |
| R31 | ? | USA only |
| R31' | ? | France only |
| R32 | ? | USA only |
| R33 | 4K7 | |
| R34 | 220R | |
| RP1 | 10Kx8 | |
| RP2 | Not used | |
| RP3 | 10Kx5 | Keyboard pull-ups |
Capacitors |
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| C1,7 | 47pF | |
| C2,4 | 47nF | |
| C8,9 | 47nF | |
| C3 | 22uF | Electrolytic |
| C5 | 1uF | Reset |
| C6 | 100pF | |
| C10 | 10nF | Tape input decoupler |
| C11 | 47nF | Tape output low-pass filter with R27 |
| C12 | 47pF | Tape output high-pass filter with R29 |