WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

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WhitakerAudio
5.3 Assembly of the Transistorized Stereo Preamplifier Module
Check the shipping box for the major component groups. Find the preamplifier box. Set the other
boxes aside for now. Organize the components in a logical manner, grouping resistors together,
capacitors together, and so on. Note that a schematic diagram of the preamplifier is provided,
along with a copy of the PWB component layout. The component layout sheet is a useful
reference as many of the part numbers are obscured when the components are installed. The
estimated time required to complete assembly of the preamplifier PWB is two hours.
After reviewing the Construction Techniques section of this manual, begin populating the
board. As the packing envelopes are used, set them aside for recycling. Before beginning, clean
the soldering iron tip.
Note that the preamplifier module consists of two separate circuit boards—the main PWB and
a buffer amplifier on a daughter board PWB. Unless otherwise stated, all instructions the follow
apply to the main PWB. Parts that are to be installed on the daughter board PWB are
identified with an asterisk* .
– Install the “quick disconnect” male tabs using the pads provided on the board. There are
four positions on the main PWB and two on the daughter board PWB. Solder in place.
Note that the mounting pins fit tight into the board. This is normal. Use a pair of pliers to hold
the tab while inserting the pins into the PWB. Make sure the PWB is resting on a soft flat surface
while the tabs are installed. It is most efficient to install all of the tabs and then turn the board over
and solder in place. Be careful to not damage the board while installing the tabs. While not strictly
necessary, it is recommended that the flat side of the tab be oriented so as to face the same
direction for all posts.
The proper procedure is illustrated in Figure 5.1.
Clean the soldering iron tip before moving on to the following steps.
– Install R101, R111 – 82 k
Ω
, 0.5 W . Solder in place.
Caution: leads may tend to fly toward the face when they are cut. Wear protective glasses. For
all steps that follow, excess lead length should be trimmed after the component is soldered in
place.
– Install R102, R112 – 180 k
Ω
, 0.5 W . Solder in place.