Commodore 1541 Maintenance Manual page 26

The remaining Computer circuits operate the same on both
versions.
3. Encoder/Decoder Circuit
The entire Encoder/Decoder circuit on the VIC-1541 has been
replaced by UCl on the 1541. Internally, UCl performs the
same functions as the following !C's did on the VIC-1541:
UE3,UF4,UE5A,UE5B,UF3,UC1B,UF5B,UF5A,UC2,UD2,UC3,UE4,UD3 and
UF6B.
4. Read Circuit
UF6A on the VIC-1541 has been replaced by pins 23,24 and 25
of UCl on the 1541. The remainder of the Read circuit
operates the same on both versions.
5. Write Circuit
UC1D,Uf5D,UF5C and UG2C on the VIC-1541 have been replaced by
pins 2,40 and 6 of UCl on the 1541. The remainder of the
Write circuit operates the same on both versions.
6.Track Select Circuit
UE2 and UF2D on the VIC-1541 have been replaced by pins
5,15,16,17 and 18 of UCl on the 1541. The remainder of the
Track Select circuit operates the same on both versions.
7. Power Supply Circuit
Other than differences in capacitor values and in the number
of bypass capacitors, there are no changes in the operation
of the Power Supply circuit. The 1541 requires fewer bypass
capacitors than the VIC-1541 because it has fewer IC's to
bypass.
8. Optics Circuit
There are no differences in operation of the Optics circuit
between the two versions.
9. Drive Motor System
There are no differences in operation of the Drive Motor
System between the two versions.
Initial Configuration
On the 1541, the device number programming pads are located near
the front of the Disk Controller PC Board. Refer to Figure B-2.
Performance Test-no change.
Calibration-no change.
Disassembly/Reassembly-no change.
Preventive Maintenance-no change.
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