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PPM3 Page 15
PPM3 PHONE PATCH MIXER ASSEMBLY
Assembly of the PPM3 is easy but still requires some time and patience. We
will start with the surface mount parts and get them out of the way.
As with any static sensitive parts be careful when installing the IC’s in this
kit. Don’t rub your feet across the carpet and then grab the chip out of your kit
as it may be damaged. It’s helpful to ground yourself to a metal object before
picking up and installing the next three parts.
1. Install U3, the SSM2165-1S surface mount IC. Be sure you have it
lined up with the silkscreen on the PC board so that the notched or dotted
end of the component is placed correctly. In the case of U3 the notch
points toward C13. The dot or notch indicates pin 1 (the pin beneath the
notch if the notch is to the left) and the rest of the pins are counted by
going around the chip in a counterclockwise direction. Tin one pad and
then line the IC up so that all the other pins are placed over the pads they
will be soldered to. Once the chip is lined up correctly, carefully solder the
pin to the pad that was tinned. Make sure that the rest of the pins are lined
up well before soldering a pin on the opposite side of the chip, then
continue around and solder all the pins. Be careful not to bridge the traces
between two of the legs of the chip.
2. In the same way, install U1. The notch or dot on this chip is placed
toward C30, opposite of U3 that you just installed. Follow the same
method and be sure that the pins line up well before soldering them all
into place.
Whew! That was some work. But the toughest two parts have been placed.
Check over your work to be sure there are no unwanted bridges and that the
pins all look soldered. Now let’s move on to the larger through-hole
components.
3. Install U2, the LM6484AIN IC. Follow the PC board silkscreen and
Parts Layout Diagram for proper orientation of this part. The dot or notch
on one end indicates pin 1. The chip must be placed correctly or it will not
work. Be sure to solder all 14 pins. We’re soldering this part in first so that
you can let the board sit on it to keep the part flush to the PC board.
Simply solder in one corner pin, make sure the others are all through the
board equally, and then solder the other corner pin. Check flatness again,
then you can solder the rest of the pins
4. Install C21, 10uF electrolytic capacitor. Electrolytics are polarized and
must be installed correctly or they tend to explode. You’ll see a marking
on the PC board to indicate the positive lead. On the part itself you’ll see a
band or stripe down one side; this indicates the negative lead. This lead is
typically the shorter of the two leads as well. Be sure to orient the part so
that the positive lead goes in the hole marked with a ’+’ sign, then solder
the part in place.