Instruction manual

FM-100 Page 19
A. DISPLAY BOARD
We will begin with the display board oriented in the direction shown. Be sure
not to confuse the sides of the board where the parts go. On the board you will
see the side marked FRONT, which is where most parts are mounted. We will
begin with lower parts and work up to the higher ones. Don’t use sockets for
these parts since they need to fit between the front panel and the PC board.
 1A. Install R87, a 1K ohm resistor (brown-black-red).
 2A. Install R59, another 1K ohm resistor (brown-black-red).
 3A. Install R13, a 8.2K ohm resistor (gray-red-red). This resistor sets the
current to each of the display segments and LEDs driven from U3.
Lowering the value of this resistor increases the brightness of the display,
but then the display will draw more current. This resistor was selected for
best brightness/current trade-off.
 4A. Install U12, one of the LM3915 Log scale bargraph driver ICs. Make
absolutely sure before soldering that you have installed all 18 pins into the
appropriate holes. Also check the notch or dot indicating pin one is facing
in the same direction as shown in the parts layout diagram. Solder all 18
pins, checking for solder bridges when done.
 5A. Install U5, the other LM3915 Log scale bargraph driver. Again make
sure all 18 pins are through the board and that the IC is in the correct
orientation.
 6A. Install U3, the MM5451 40 pin IC. Again make sure the notch is in the
same direction as shown in the parts layout, and that all 40 pins are
through the board before soldering. This IC drives all the individual
segments of the display without multiplexing it.
 7A. Install D12, one of the ten segment bargraph displays. You will notice
a small divot or notch on one corner of the bargraph indicating where pin 1
is. This will be installed in the same orientation as the notch in the parts
layout diagram. Solder all 20 pins.
 8A. Install D11, the other 10 segment bargraph display. Make sure to align
this in the same way as before and solder all 20 pins.
 9A. Install DS2, one of the two digit displays. Notice how there isn’t any
indication of pin 1 on these. In this case we want to orient the lettering on
the one side towards U3, so that when looking at the display, the lettering
is facing downward. Solder all 18 pins.
 10A. Install DS1, the other two digit display. Again orient the lettering