WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Manual

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– Install R47 – 5 k
Ω
, trimmer – on the right channel speaker PWB. Solder in place. Set for
center of travel (7 turns from either stop).
– Install R48 – 5 k
Ω
, trimmer – on the left channel speaker PWB. Solder in place. Set for
center of travel (7 turns from either stop).
– Install R49 – 10 k
Ω
, 0.5 W – on the right channel speaker PWB. Solder in place.
– Install R50 – 10 k
Ω
, 0.5 W – on the left channel speaker PWB. Solder in place.
In the next few steps, the speaker load resistors will be installed. As shown in the schematic
diagram of Figure 1.1, when the speaker switch is in the Off position, the secondary of each
output transformer is switched by a relay to a load resistor. The specified value for the resistor is 8
Ω
. This value can be difficult to find in stock components and so in this implementation, two 4
Ω
10 W resistors are connected in series to yield the correct value.
– Install R14 and R15 – 4
Ω
10 W – on the right channel speaker PWB. Mount so the
devices are about 1/2-inch above the PWB. Solder both devices in place.
– Install R31 and R32 – 4
Ω
10 W – on the left channel speaker PWB. Mount so the devices
are about 1/2-inch above the PWB. Solder both devices in place.
– Install R16 and R17 – 27
Ω
2 W – on the right channel speaker PWB. Solder.
– Install R33 and R34 – 27
Ω
2 W – on the left channel speaker PWB. Solder.
– Install R66 – 270
Ω
2 W – on the right channel speaker PWB. Solder.
– Install R67 – 150
Ω
0.5 W – on the right channel speaker PWB. Solder.
– Install R68 – 270
Ω
2 W – on the right channel speaker PWB. Solder.
– Install R69 – 150
Ω
0.5 W – on the right channel speaker PWB. Solder.
– Install C6 – 200 pF – on the right channel speaker PWB. Solder in place.
– Install C12 – 200 pF – on the left channel speaker PWB. Solder in place.
– Install D1 – 1 A 600 V diode – on the right channel speaker PWB. Solder in place.
– Install D2 – 1 A 600 V diode – on the left channel speaker PWB. Solder in place.
– Mount the relay RYL1 socket on the right channel speaker PWB. Solder in place.