Board Revisions
Board Revisions
| ASSY Number |
Year |
Key Differences
|
| 001 |
1980 |
Original design with basic components.
|
| 002 |
1981 |
Improved power supply circuit and minor layout changes.
|
| 003 |
1982 |
Enhanced memory management and additional ROM features.
|
Power Supply & Regulator Care
The Sinclair ZX80 utilizes a simple power supply and regulator setup. Below are the recommended PSU models, common failure modes, and on-board regulator capacitor information.
PSU Models
- Sinclair ZX80 Power Supply (Original)
- Third-party 9V DC adapters (ensure correct polarity)
Common Failure Modes
- Overheating due to inadequate ventilation.
- Voltage drop under load leading to unstable operation.
On-board Regulator Capacitors
- C1: 100µF, 16V (Electrolytic)
- C2: 10µF, 16V (Electrolytic)
Capacitor Replacement (Recap)
Capacitor Replacement (Recap)
| Board Position |
Capacitance |
Voltage |
Notes
|
| C1 |
100µF |
16V |
Replace with low-ESR 105°C part.
|
| C2 |
10µF |
16V |
Replace with low-ESR 105°C part.
|
| C3 |
100µF |
16V |
Replace with low-ESR 105°C part.
|
| C4 |
1µF |
50V |
Replace with low-ESR 105°C part.
|
Voltage & Clock Test Points
Voltage & Clock Test Points
| Test Point |
Location/Pin |
Expected Values
|
| TP1 |
Near C1 |
+5V
|
| TP2 |
Near IC1 |
+12V
|
| TP3 |
Near IC2 |
Clock signal: 1.77 MHz
|
