Converting a Tandy Joystick to use with the Vectrex =================================================== These instructions relate to the Tandy 26-3123 Deluxe Joystick only. The main problem in converting the joystick for use with the vectrex is that the sense of the vertical axis needs to be reversed. Since the potentiometers in this unit are formed by resistive traces on a plastic plate (the 'Pot Plate'), it's not a simple matter to reverse the connections to one of the pots. Here's how to do it. 1) Remove the 4 screws from the underside of the joystick, and take off the lower cover. Set these parts aside 2) Carefully lift up the 'Pot Plate', and note where the wires are connected. Disconnect the wires. Note that 2 of the connections are linked by a (red) wire. 3) Disconnect the wires on the PCB. Note where the 3 wires (white, red, black) which go to the switches in the joystick handle are connected. Set the joystick cable aside. You'll need to recover the push-on tags from this cable later. 4) Remove the 2 screws, the PCB, and the fire button + springs. Set these parts asside for the moment. 5) Note how the joystick mechanism is assembled. The aim is to rotate the 'Pot Plate' and the sliding contacts counter-clockwise by 90 degrees. To do this, first unclip the 2 return springs from the mechanism 6) Lift out the pivot from the centre of the sliders, and then remove the sliders. Note how they are fitted 7) Remove the plastic base from the joystick mechanism. You need to rotate this through 90 degrees also, so that the sliders will fit correctly. In order to do this, enlarge the hole that will be in the lower right corner using a 7.5mm drill from the side that faces the joystick handle, until the plast base will fit correctly in this orrientation. 8) Now you start reassembling the parts. Refit the plastic base (rotated through 90 degrees), the sliders (metal contacts on the left and top as you look at them), the central pivot, and the return springs (over the top left and bottom right bosses). 9) Slide the fine trim controls off the pot plate _carefully_. Hold the pot plate so that the track side is uppermost, the connection pads are on the top and right sides, and the fine trim controls are on the bottom and left sides. Refit the fine trim controls by sliding them on, takeing care to avoid damaging the contacts. 10) Use the socket end of a Sega extension cable for the connection to the Vectrex. Remove about 4" of outer covering from the cable, and recover 3 clips from the original cable. Do not touch the red jumper lead for the moment. 11) Crimp and solder these tags to the Green (pin 5, Pot0), Blue (Pin 6, Pot 1) and Grey (pin 7, +5V) on the cable. Now cut the red jumper wire complete wit it's tags from the original cable. Solder the white lead from the cable to one tag on the jumper wire. 12) Reconnect the leads to the pot plate in the following way, seen from the track side White + Red Jumper (-5V) / Blue (Pot 1) / / Grey (+5V) / / / / / / +-----####------####----####-----+ Green (Pot 0) | | / | # / | # / | # | | | | | | | | | | Red Jumper | # / | # / | # / | | +--------------------------------+ 13) Now take the PCB you removed earlier. Carefully desolder the slide swtich from it. Also cut the track between the fire button on the PCB and the first connector slot on the edge. 14) Connect 3 more wires from the cable to the holes left vacant by the removal of the slide switch as shown. ^ ^ | Notched edge of board, viewed from component (non-track side) | (Sw3) (Sw4) Orange----o o---- Yellow o o Red-------o o (Sw2) 15) Connect the black lead of the cable (0V) to the far left slot on the PCB. This slot is connected to all the other slots on the left of the fire button. 16) Re-install the fire button, the PCB, and the screws. 17) Reconnect the leads from the joystick handle to the PCB, in the same positions as they were originally. 18) Position the pot plate over the joystick mechanism. Use 2 of the cover screws to hold it in place 19 Plug the joystick into the vectrex, and use the joystick test in the diagnostic ROM to test it. 20 Cut a slot in the left side of the cover to allow the fine trim control to protrude. Copy this slot from the one on the right side, and file down the lower part of the cover in a similar way. 21) Use a couple of cable ties to make a strain-relief to hold the cable in the slot in the joystick body. 22) Remove the screws you fitted to hold the pot plate in place, fit the cover, and secure it with the 4 screws.