Sinclair ZX80 General Maintenance

Sinclair ZX80 Mainboard

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