This board replaces the dial light bulb on the Dynaco FM3 with a LED.
The kit ships with a clear LED and a 390 Ohm resistor to give off light similar to what the bulb did but uses way less power.
If you want to get fancy and have a different colour LED, use the following chart to choose the resistor required. You do not have to be exact, just do not go way lower as it will exceed the 20ma limit on most 5MM LEDs. The voltage after the diode and resistor is 9V if you want to do your own calculation with your LEDs particulars.
| COLOUR | V DROP | BRIGHT (20ma) | DIM (15ma) |
| RED | 1.8 | 360 | 480 |
| ORANGE | 2 | 350 | 466 |
| YELLOW | 2.1 | 345 | 460 |
| GREEN | 1.9 | 355 | 473 |
| BLUE | 2.4 | 330 | 440 |
| CLEAR | 3.2 | 290 | 386 |
| WHITE | 3.5 | 275 | 366 |
Solder in the diode, resistor, 10uF capacitor and LED as per the silkscreen. For the capacitor you have to bend the leads at 90 degrees so it lays flat on the board. Note the orientation of the LED, diode and the negative side of the capacitor, Ensure you have these correct. The diode has a white line, the cap has a white line and the LED has a little flat edge.
Use the 20-22 gauge solid wire to make leads at the bottom.
If you want to control the brightness, omit the resistor and use a 500-ohm multi turn pot. Bend the legs on the pot 90 degrees so the pot lays flat on the board with the adjuster on the left. Solder the pot in and before you install it, put your multimeter probes on TP1 and TP2 and set the resistance to what you see on the chart above for the colour of the LED you are using. Once installed you can adjust the pot to the brightness you prefer. Do not adjust it too low as you could burn out your LED.
To install the board, you need to unsolder the old light bulb holder. There is generally quite a bit of solder so you may need to use a solder sucker. Once you have the holes cleaned up, put the leads on the board through the holes so the LED lines up with where the bulb used to and solder them. Be careful with height as you want the LED to line up with the hole in the faceplate. Once installed you can bend it around a bit to make it line up perfectly.
