This article is reproduced by permission from the March, 1989 MIDWEST NEWS, the monthly journal of the Midwest Commodore Users Group. Permission is granted to reproduce this article for non-profit purposes only. The author and MWCUG assume no liability for any damage caused by following the procedures outlined in this article. Use a doodle viewer/printer to view the file DDDIAGRAM included.
The DATASETTE'S SPLIT PERSONALITY
By: Rick Dixon
Please see DDDIAGRAM for sketch.
"Take those old records off the shelf, sit and listen to them by yourself." (Bob Seger)
Or more appropriately,"Take those old cassettes off the shelf and sit and listen to them on your C64 or C128". With the information in this article you'll be able to do just that, listen to your favorite tapes through your computer and monitor. So, get your old Commodore Datasette from in front of the door and find something else to hold the door open. Or, take the tape drive out of hiding and dust it off.
Before we get into the nuts and bolts of the procedure I must warn you that opening the case of the datasette will void any warranties, (If it is still under warranty which is highly unlikely). Likewise, opening the computer will void its warranty, and of course, neither the author of this article or MWCUG are responsible for any damage these changes may cause to your equipment.
The idea for this hardware modification sprang from a conversation with Pete. He was explaining how college students were attaching their personal tapeplayers to C64s and playing the tapes through the computer. He said he had tried it and it worked! A quick check of the pinout diagrams in the appendix of the computer manual revealed that pin 5 of the Audio/Video jack was labeled as "Audio In". Investigation of the schematics showed that pin 5 was connected to the SID (sound interface device) chip. This meant that not only could a tape player or other audio device be connected and played through the computer, but it's volume could also be controlled with the right poke command in the C64 or by the volume command in the C128. With this information came more questions. Why couldn't the Datasette be used as a tape player ? How would you hook it up if it could play tapes ? We needed to find the answers to these questions and so the experimentation began. What follows is the result of that work.
There are three ways to approach this project. The first has the amplifier enclosed in the datasette with the switch and audio jack protruding from the case. The second involves placing the parts entirely inside of the datasette. This version gives a clean self contained unit. The third requires bringing the required wires out of the datasette and into the amplifier and then into the computer.
You will need the parts listed at the end of this article as well as a soldering iron, some solder, a pair of wire cutters and a drill with drill bits.
Although the unit I build did not contain a switch or RCA jack, I have included a switch in this version to protect the CIA chip and an audio jack for a cleaner appearance. You can eliminate these if you want. I've noted how in the procedure below.
Procedure
1. Remove the back from the Radio-Shack amplifier.
2. Remove the nuts holding the jacks of the amplifier to the case of the unit.
3. Cut the wires to the battery terminals, cutting them as close the battery contacts as possible.
4. Remove the screw that holds the amp in the case.
5. Cut the speaker leads as close as possible to speaker.
6. Set the case , case hardware and battery contacts aside.
7. Turn the the amplifier board component side down.
8. Solder a short 3" wire to the rear pin of the input jack. (see diagram A. Doodle File DDDiagram) Skip to step 12 if you are not going to use a switch
9. Solder the other end of this wire to one of the center pins of the switch,as shown in A.
10. Solder another 3" wire to switch as shown.
11. Solder the two remaining wires to the switch just as the Doodle file shows.
12. Solder the positive speaker wire (the red one) to the center connector of the RCA jack. If you do not want to put a hole in the case, connect a long wire to the speaker wire and solder the jack to this wire which you will bring out through the existing cable slot in the back of the unit.
13. Cut the black speaker wire as close to the board as possible.
14. We are done with the circuit board for now, so place it out of the way.
15. Take the datasette and place it upside down on a soft cloth.
16. Remove the screws which hold the two halves of the case together.
17. Take off the bottom and set it aside.
18. Remove the cardboard circuitboard protector.
19. (If you are not using a switch or jack skip this step and step 20.) Pick a location and drill two holes. One for the switch and one for the jack. Keep in mind the length of the wires you've soldered to the switch.
20. Mount the switch and jack to the case with the hardware provided.
21. Locate the datasette motors power leads at the rear of the datasette's circuitboard. Solder the amplifiers power leads to the datasette board at the location of the motor leads. As shown in Diagram B. (Red to red and Black to black)
22. Solder the wire from the input connection of the amplifier board to the datasette board as shown in B. This should be the playback head of the datasette.
23. (If you are not putting in a switch skip to step 25.) Disassemble the datasette's plug to determine the color of the Cassette read wire. It is the one connected to D4 on the Cassette port at the rear of the computer. See you C64 manual Appendix b for the diagram of the connector.
24. Once you have determined the cassette read wire, locate that wire at the circuit board inside the datasette and cut it in two. Be sure to cut it so that you can get to both sides of the cut wire.
25. Now connect the remaining two wires from the switch to the wire you have just cut. Solder them in place.
26. Position the amplifier inside the case so that it will not move. (A piece of cardboard works fine.) Reassemble the datasette case. If you are not using a jack mounted on the case bring the wire out the back of the datasette.
27. All that remains is to connect a wire from the RCA jack on the datasette to pin five of the Video jack of the C64 or C128.
28. There are several ways to do this. You can purchase a video cable which has pin five connected. Or, you can make your own. Or, you can do as I did and use the ground wire from the Datasette (unless you're one of those real cautious people, you know the ones I mean, those who run around the house unplugging everything at the mere threat of lightning.) I'll explain how to use the grounding wire next month.
If you do not want to place the amplifier in the datasette then solder two wires to the datasette board as shown in diagram C and bring those out the back of the datasette. Terminate these wires with the correct plug for the input of the amplifier. Place a battery in the amp and a cable from the amp's output to pin five of the computers audio/video plug.
If you have any questions talk with me at the club meeting. I will bring my unit next month's meeting so you can see what the final product looks like.
In next month's newsletter I'll present some other uses for your modified datasette besides just playing music. So stay tuned and don't touch that dial.
PARTS LIST
1 Amplifier/Speaker (Radio Shack
1 RCA style audio jack (Radio Shack #274-346) (optional- see text)
2 Feet of wire
1 DPDT switch (Radio Shack #275-626) (optional- see text)
