The XH1541 adaptor

You should follow these instructions if your drive already has a Commodore parallel cable and you want to make use of it. In this case, you'll have to build an adaptor, through which you can connect the cable to the PC parallel port.

Important notes

• Don't use a PCB-mountable parallel plug for this adaptor. If you use a solderable plug, one that is usually used for cables, then you can make your adaptor significantly smaller.
• The circuitry will be on the upper side of the adaptor. It is very important, however, that you'll have to connect the lower side of the user port plug onto it, that is, upside down.

Construction

You need the following parts to build this adaptor:

• One printable circuit board of about 5.5 x 3 cm
• Eight diodes (e.g. 1N4148)
• One solderable 25-pin male plug (PC parallel plug)

Step 1. Create the direct connections on the board, between the user port edge and the parallel plug. These include the following connections:

To make the board single-sided, you may omit the GND connection.

Step 2. Create the diode connections on the board, between the user port edge and the parallel plug. These include the following connections:

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

Step 3. 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.

Step 4. Solder and then glue the board between the two pin rows of the parallel plug. The upper side of the adaptor, the one with the circuitry, should be levelled with the longer side of the parallel plug, the one with thirteen (13) pins.

Circuit diagram:

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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