WARNING
Danger of severe electric shock.
Do not operate the power supply without observing all the proper safety precautions.
Do not operate with the covers removed.
If in doubt consult a qualified electrical engineer
The Sirius 1 comes fitted with one of two types of power supply made by different manufactures. As can be appreicated the level of failure increases as the components age. Generally try to avoid long periods of power down. Power up the computer at regular intervals but avoid rapid switching on and off.
COMPOWER
This is the most common power supply fitted. Should this power supply fail a large number of components will have to be replaced. Due to the low impedence of the primary circuit all components should be removed before testing.
The usual components to fail are:
Transisors
Q102 - 2N2219
Q103 - Marked SJ6942 or similar - Subsitute with 2N6545 or BU526
Diodes
D110 - IN4004
Capacitors
C103 - 33�F / 10 volt
C108 - 3.3nF / 600volt - Subsitute with 3.3nF / 4Kv (disc ceramic)
C111 - 4.7�F / 10volt Tantalum - Subsitute with 4.7�F / 35 volt
Resistors
R106 - 1 ohm / � watt (used as a fusible resistor)
Once the supply is working adjust R116 to give 5 volt output on full load.
ASTEC
This power supply is slightly better than the Compower supply in respect of its higher current capability and cooler running. This power supply is fully self regulated i.e. no presets to adjust the output so voltages may vary from that specified i.e. 5 volts and 12 volts. Capacitors should be checked for leakage.
Components likly to cause failure:
Transistors
Q1 - Marked D467 - Substitute with BC635 or BC639
Q2 - Unmarked - Substitute with BU208 or BU208A
Capacitors
C9 - 220�F 10 volt - Substitute with 220�F 25 volt
If you have any other solutions to add to this page please email them in for inclusion and a mention on the contributors page.
Note: The information above is used at your own risk and implies no warranty as to its suitability as a repair. No responsibility can be accepted for any accidents or injuries as a result of using the information. All liability rests with you.
