The XXH1541 cable combo

You should follow these instructions if you already have an X1541 cable and you want to transform it.

Important notes

• Because you will solder a cable onto some pins of the VIA#1 chip inside the drive, you will have to first make sure that these pins are not used for any other purpose. This depends on the version of the drive you have:
  • In original Commodore 1541 drives, nothing is defined to any of the bits of Port A. You can solder the cable without any problem.
  • In 1541C drives, bit 0 of Port A is used for the detection of the head being over track 1. After stripping this connection off of the chip, you will have to replace the DOS ROM with that of the 1541 or the 1541-II. Otherwise you'll get strange results when the drive is seeking: the DOS tries to rely on the detector line which doesn't exist anymore.
  • In 1541-II drives, bit 0 of Port A is grounded, strip this connection off of the chip.

Construction

You need the following parts to build this cable:

• One solderable 15-pin male plug (PC game plug)
• Eight diodes (e.g. 1N4148)
• A shielded or unshielded 8-wire cable of, preferably at most, 2 meters

Step 2. Solder those wires of the cable, that don't go through a diode, on the other end of the cable onto the parallel plug. These include the following connections:

Step 3. Solder the remaining wires of the cable through a diode onto the parallel plug. These including the following connections:

The cathodes should be pointing towards the pins in the right column of the table.

Step 4. Build the diode bridges between the appropriate pins of the parallel plug. These include the following connections:

The cathodes should be pointing towards the pins in the right column of the table.

Circuit diagram:

The original connections of the X1541 cable are shown in grey. You can find the description of all parts used on the diagrams at the legend page.

Source: The Joe Forster-STA homepage

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