Commodore 1540/1541 Service Manual: Power Supply

1541 CIRCUIT THEORY

All circuit diagrams have been taken from the short board schematic 1540049 unless otherwise noted. The short board use a 6116 RAM which replaces the four 2114 I.C.s on the long board. See page 11 for the Read/Write logic differences.

The Power Supply

The input AC voltage is controlled by switch 1 (SW1). Disk circuit protection is provided by fuse 1 (F1). If SW1 is closed, the AC voltage input is applied to the primary winding of transformer one (T1). T1 steps down th AC input voltage into two smaller AC voltages. The top secondary AC output (approx. 16VRMS) is converted to DC by the Full Wave Bridge Rectifier CR1. The DC output of CR1 is regulated at 12VDC by VR1. The bottom secondary AC output of T1 (approx. 9VRMS) is converted to DC by the Full Wave Rectifier CR3. The DC output of CR3 is regulated at +5VDC by VR2. High frequency filtering is provided by C1 and C3 for the 12VDC supply, and C4, C6 to C9, C22, C27 to C30 for the 5VDC supply. Low frequency filtering is provided by C17 and C2 for the 12VDC supply, and C5 and C16 for the 5VDC supply.

This page has been created by Sami Rautiainen.
Read the small print.	Last updated September 05, 2020.