The Cheapest and Easiest Way to Upgrade Turn Signal Lamps of Vespa Vintage Series(50,100,125 Primavera,ET3) to LEDs.

Vespa Vitage series are ones of most popular survivor of motercycle evolution.They only have simple 2-stroke engines, steel frames and very poor electric equipments.
Original models (to be sold in Japan) have pairs of bar-end type winkers. But their 6V/18W incandescent bulb are too dark to catch other drivers' attention.
Bulb replacement with LEDs is now the most ideal way to improve this problem.But Most old type Vespas do not have voltage regulators. so the higher its engines rotational speed is , the higher the voltage of its electric system.If rev up to red line, the voltage would jump over 25V. Almost all LED equipments cannot sustain such broad voltage range.

Materials

1) 1W yellow LED unit. 70JPY 8 pcs

2) hexangular PCB for LED. 20JPY 8 pcs

3) LED drivers for upto 3 pcs 1W LED 140JPY 4 pcs
http://akizukidenshi.com/download/ds/optosupply/OSMR16-P1231.pdf

4) Nylon or brass standoff spacers and screw. Joint then so as to be as same length as original festone bulb.At least one of spacers MUST be Nylon or other insulating materials 100-200 JPY 2 sets

5) 6V voltage regulator for small moterbike i.e. HONDA MONKEY etc. 1400JPY

6) Turn signal relay for LED (2 pin or 3 pin) 300-600JPY

Totally, it costs 3020JPY - 3520JPY (about $30-$35)

Build a Unit

Solder LEDs on PCBs and connect a pair of units serially with wire.

Connect a Pair of LEDs to a Driver Unit

Remove input pins of driver unit with soldering iron, and solder wires. Another end of wire must be stripped 25cm.

Connect Driver Units to Electrodes

Joint spacers to make electrodes.Then insulate them. One of driver units input wire twist together with the one of other driver unit's input wire, make small ring and plate with solder so as not to tear off and connect input wires to electrodes.

Set Up Turn Signal

Remove flasher bulb, Put new LED modules on. It must be a little bit tight, spout them carefully.

Install Voltage Regulator-rectifier and Turn Signsl Relay

The LED driver units’ allwable voltage fluctuation range is about 5V to 15V. Without voltage regulator, if generated voltage get higher, the protection circuit will work. If voltage increases further, driver circuits and LEDs will break.

Generally, voltage regulator-rectifier for motorcycle has four pins. Pin assign is shown on photo.
Output current of regulator- rectifier is still pulse wave. Without smoothing capacitor, LEDs will always blink rapidly.