Important notes

• You definitely need BSV52 transistors and 4.7 kOhm resistors for this cable, different parts may make the cable inoperable.

• 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.

• On circuit diagrams, plugs are displayed as viewed from the back side, the solder side. Chips are displayed as viewed from above; also, see the small semicircular cut for finding the correct orientation. When in doubt, see the corresponding description on the legend page.

Construction

First, create the parallel port for 1541 drives or the parallel port for 1570 and 1571 drives.

You need the following parts to build this cable:

• One solderable 6-pin male DIN plug (Commodore serial plug)

• One solderable 15-pin male plug (PC game plug)

• One solderable 25-pin male plug (PC parallel plug)

• Four BSV52 transistors

• Four SMD 1206-style 4.7 kOhm resistors

• A shielded 4-wire or unshielded 5-wire cable of, preferably, at most 2 meters

• A shielded or unshielded 8-wire cable of, preferably, at most 2 meters

Step 1. Solder one end of the 5-wire cable onto the DIN plug.

Step 2. Solder those wires of the 5-wire cable, that don't go through an amplifier, on the other end of the cable onto the parallel plug. These include the following connections:

   DIN plug   
 Parallel plug 

    2, GND     
18-25, GND     

    3, ATN     
   13, Select  

    4, CLK     
   12, PaperEnd

    5, DATA    
   10, Ack     

    6, RESET   
   11, Busy    

Step 3. Build the amplifier bridges, consisting of one transistor and one resistor each, between the appropriate pins of the parallel plug. These include the following connections:

 Parallel plug 
 Parallel plug 

   13, Select  
    1, Strobe  

   12, PaperEnd
   14, AutoFeed

   11, Busy    
   17, SelectIn

   10, Ack     
   16, Init    

The collector of each transistor should be pointing towards the pin in the left column of the table. The base of each transistor should be connected to one side of the resistor; the other side of each resistor should be connected to the pin in the right column of the table. The emitters of the transistors should be connected together to the common ground, the GND line.

Step 4. Solder one end of the 8-wire cable onto the game plug.

Step 5. Solder the other end of the 8-wire cable onto the parallel plug. You should have the following connections:

   Game plug   
 Parallel plug 

       1       
    2, Data 0  

       2       
    3, Data 1  

       3       
    4, Data 2  

       4       
    5, Data 3  

       5       
    6, Data 4  

       6       
    7, Data 5  

       7       
    8, Data 6  

       8       
    9, Data 7  

 not connected 
18-25, GND     

Circuit diagram

You can find the description of all parts used on the diagrams at the legend page.

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