2 layers
LM80C R6
leomil72/LM80C
A Z80-based homebrew computer withTMS9918, AY-3-8910, Z80 CTC, Z80 PIO, and Z80 SIO
153 parts123GPL-3.0
2 layers37.1 × 24.1 mm
ZX81-Composite
redhawk668/ZX81-Composite25ZX81 Composite video with Backporch
- Size
- 37.1 × 24.1 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 16
- Nets
- 12
- Pads
- 37
- Tracks, vias
- 105, 7
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 5 (file 20171130)
- Created
- 4 May 2021
- Updated
- 19 Jun 2021
Overview
ZX81-Composite is an open-source printed circuit board by redhawk668, from the redhawk668/ZX81-Composite repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 37.1 × 24.1 mm with 16 parts on 12 nets, routed with 105 tracks and 7 vias.
It is built around the NE555 and BC337. Its parts include 4 capacitors, 4 resistors, 3 connectors, 2 diodes and 2 transistors.
Main components
2README
README.mdZX81 Composite Video with Backporch
This PCB provides composite video for the ZX81, it replaces the internal PCB from the modulator. For ZX81's with earlier type ULA's it generates a back porch signal.
It will work with the later 2C210 ULA. However, this ULA does provide a backporch signal, so the 555 timer chip is not needed and can be removed. It is based on instructions and schematics found on zx.zigg.net.
Billing of Materials:
| Qty | Value | Component | Package | PCB |
|---|---|---|---|---|
| 2x | 10K | Metal Film Resistors | Axial DIN204 | R1, R2 |
| 1x | 68R | Metal Film Resistor | Axial DIN204 | R3 |
| 1x | 56R | Metal Film Resistor | Axial DIN204 | R4 |
| 1x | 10nF | Ceramic Capacitor | Disc 5mm | C2 |
| 1x | 820pF | Ceramic Capacitor | Disc 5mm | C3 |
| 1x | 82pF | Ceramic Capacitor | Disc 5mm | C4 |
| 1x | 22uF | Electrolytic Capacitor | Radial 6.3mm | C1 |
| 2x | 1N4148 | Diodes | DO-35 | D1, D2 |
| 2x | BC337 | Transistors | TO-92 | Q1, Q2 |
| U1 | NE555 | Timer IC | DIP-8 | U1 |
Usage:
Desolder the modulator case, remove the PCB and solder the new PCB in. Solder wires to the +5 volt input, video input and video output. Re-assemble the modulator case and solder it back on the ZX81 board. Connect video output with the RCA, connect +5 volt and video in with the correspending pads on the ZX81 board.
Parts
16| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 10K | Resistors_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal | R1, R2 |
| 2 | 1N4148 | Diodes_THT:D_DO-35_SOD27_P7.62mm_Horizontal | D1, D2 |
| 2 | BC337 | TO_SOT_Packages_THT:TO-92_Inline_Narrow_Oval | Q1, Q2 |
| 1 | +5 Volt Input | Pin_Headers:Pin_Header_Straight_1x01_Pitch2.54mm | J1 |
| 1 | 10nF | Capacitors_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C2 |
| 1 | 22uF | Capacitors_THT:CP_Radial_D6.3mm_P2.50mm | C1 |
| 1 | 56R | Resistors_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal | R4 |
| 1 | 68R | Resistors_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal | R3 |
| 1 | 820pF | Capacitors_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C3 |
| 1 | 82pF | Capacitors_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C4 |
| 1 | NE555 | Housings_DIP:DIP-8_W7.62mm | U1 |
| 1 | ULA Pin 16 | Pin_Headers:Pin_Header_Straight_1x01_Pitch2.54mm | J2 |
| 1 | Video Out | Pin_Headers:Pin_Header_Straight_1x01_Pitch2.54mm | J3 |
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Questions
How big is the ZX81-Composite PCB?
It measures 37.1 × 24.1 mm and has 2 copper layers, 1.6 mm thick.
What parts does the ZX81-Composite use?
16 parts, built around the NE555 and BC337. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the ZX81-Composite KiCad files?
From the redhawk668/ZX81-Composite repository on GitHub, at the commit this page was made from: the board is Rev. A/ZX81 Composite.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the ZX81-Composite design in my own project?
Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).