The original turn signal control unit (the unit under the battery tray which controls the self

cancelling function of the turn signal) is encapsulated in an opaque epoxy to protect it from

environmental damage. Unfortunately this also obviates any repairs should the unit fail.

I have been unable to source any replacement part except the odd second hand unit on the

internet, the only one of which I bought was also inoperative. This prompted me to design and build

my own from modern components.

For producing the printed circuit board

The components

Miscellaneous

Print the circuit board mask onto tracing paper (use a laser printer).

Place the printed mask onto the glass of the light source printed side up.

Mix up a solution of caustic soda in water (1 heaped teaspoon in 1 litre of warm water)

Peel the protective cover off the photo resist board and place the board copper side down, on

top of the mask so that the mask printed side is against the board and between the light and the

board.

Close the lid of the light source or make sure the board is pressed firmly against the mask.

Switch on the light source and leave on for 3 minutes. (This will vary with light strength,

experiment for best results)

When the board has been exposed for the optimum time, remove it and immerse it

immediately in the caustic soda solution. Brush the board gently until all of the exposed etch resist

has been removed. Rinse the board under cold running water, you now have a copper clad board

resist (exposed or not) and if it is too weak it will not remove the resist from the areas we wish to

temperature of the solution

Make up a solution of sodium persulfate in water - 125g per half litre of hot water.

Pour the solution into a ceramic or plastic flat bottomed container.

After about 5 to 10 minutes, all the copper not covered with the etch resist will have

disappeared leaving the desired printed circuit.

Rinse the circuit in running water and dry. Carefully drill each of the Pads using a 0.7mm

drill. The pads will have holes etched in them from the etching process which helps alignment.

Make sure the pads for the chips are carefully drilled otherwise you will have difficulty fitting the

chips. Carefully open up the holes in the pads for the transistor and the wires using a 1mm drill.

You must now decide which distance you prefer (42 meters or 84 meters see below) and cut

the appropriate track to suit. (I chose the 84 meter option)

Using a poliblock or a lightly abrasive substance, clean off the etch resist from the tracks.

Mount the components and solder them in place starting with the diodes, then the resistors, then the

transistor and the OP amp, then the Capacitor, the wires (about 3”long. Lastly (this is because the

CMOS devices are sensitive to static electricity and may be damaged just by touching them) mount

the CMOS chips taking care to either not touch the legs of the chips, or ground yourself and the

chip before touching it. The CMOS devices come wrapped in silver foil or mounted on conductive

foam. Do not remove this until the last minute.

Once all the components are mounted and soldered in place, wrap the board in cooking foil to

protect the CMOS components until the circuit is tested and encapsulated.

Connecting the wires to the connector is the next step. I believe that its best to use the old

connector and wires, so cut the wires from the old circuit close to the box, this will leave you with

the colour coded wires and the connector also the light green and red wires with bullet connectors

male and female on. Cut eight pieces of heat shrink tubing about ½ inch long. Strip the wires on

both the board side and the connector sides to about ¼ inch. Tin the wires with solder and put one

length of heat shrink tubing over each circuit board wire. DON’T FORGET TO PUT THE WIRES

THROUGH THE LID OF THE BOX FIRST Solder the appropriate wires together and cover each

one with the heat shrink tubing. Heat the tubing with a hot air source (lighter or soldering iron) to

shrink the tube into place.

Once the circuit is complete it must be tested to make sure there are no problems before

encapsulating it. Once encapsulated, there is nothing that can be done if faults are present except

remaking the entire circuit.

Connect the six pin connector and the two bullet connectors to their appropriate places.

Method 1

1.Put the bike on the centre stand and jack the engine so the front wheel is free to rotate.

2.Switch on the ignition and make sure the turn controller power switch is on.

3.Connect a voltmeter or 12v bulb between the red distance sensor wire and ground.

4.Place the turn switch either left or right and start counting.

5.Within 10 seconds (approx 7 seconds) voltage should be present at the red distance sensor

wire. (If not, troubleshoot the fault).

6.If the voltage is present, centre the turn switch. Then place it back to the right or left position.

7.After the time delay noticed above, spin the front wheel approx 21 times (42 metre setting) or

42 times (84 meter setting). (The wheel is approximately 2 metres circumference.) The

switch should centre itself.

(If not, troubleshoot the fault).

Method 2

1. Disconnect the speedometer drive from the front wheel.

2. Switch on the ignition and make sure the turn controller power switch is on.

3. Connect a voltmeter or 12v bulb between the red distance sensor wire and ground.

4. Place the turn switch either left or right and start counting.

5. Within 10 seconds (approx 7 seconds) voltage should be present at the red distance sensor

wire. (If not, troubleshoot the fault using the system diagram below).

6. If the voltage is present, centre the turn switch. Then place it back to the right or left

position.

7. After the time delay noticed above, turn the speedometer drive using a battery drill approx

250 times (42 metre setting) or 500 times (84 meter setting). (The wheel is approximately 2

metres circumference and the speedometer drive turns 12 times per revolution of the wheel)

The switch should centre itself. (If not, troubleshoot the fault using the system diagram

below).

Once the circuit is proven to be operating satisfactorily, fit the circuit into the box from which

the old circuit was removed. (some last minute filing and sanding of the board may be required for

an easy fit). Be sure to coat the inside of the box with silicon spray or Vaseline.

Using a potting compound of your choice – well mixed epoxy or PRC are good materials – do

not use silicon bathroom sealant (it’s corrosive and doesn’t cure well in large quantities). Fill the

box until just the edge of the board is visible taking care to leave the locating holes clear for the lid.

Leave the potting compound to cure completely and test the circuit again. If all is well fit your

new unit as you would the old one. You now have a functional turn signal cancelling unit again.

See below for:

1. System diagram

2. PCB Mask

3. circuit diagram

4. component diagram

Many Thanks to Penn for this excellent article.