Ramsey Electronics LPA1 Instruction Manual - page 13
LPA1
• 13
Now that we have completed the power circuits, we will move on to the
biasing circuit. This circuit holds the transistor output voltages in the desired
range.
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13. Install C1, .01uF capacitor [marked .01 or 103 or 10nF]. Make sure
that you crack or peel off the insulation on the legs of the capacitor.
Solder the topside connection closest to the outside of the board
(towards the switch side) on both the top and bottom sides of the board.
This capacitor is also known as a power bypass capacitor because it
bypasses any RF energy to ground.
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14. Install R1, 1K ohm resistor [brown-black-red].
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15. Install R3, 10K ohm resistor [brown-black-orange]. Solder the lead
closest to C2 on the top side as well as the bottom side. R1 and R3 hold
a constant voltage on the base of Q1. This allows Q1 to act as a current
source.
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16. Install R2, 6.8 ohm resistor [blue-grey-gold].
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17. Install R6, 1K ohm resistor [brown-black-red]. Solder the lead
closest to the LED to the top side as well as the bottom side.
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18. Find C2, .01uF capacitor [marked .01 or 103 or 10nF]. Take off the
insulation on it’s legs and install the part. Solder the leg closest to the
LED to the top side of the board in addition to the bottom connections.
Don’t forget to take the insulation off of the legs. C2 keeps any RF energy
from affecting the bias voltage on Q2.
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19. Install R7, 1K ohm resistor [brown-black-red].
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20. Install Q1, PNP transistor [marked 221334]. You will notice that the
transistor has a flat side with no writing on it. This side must face away
from the RCA jacks.
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21. Insert L1, VK200 inductor. Look for a ferrite bead with 6 holes and a
piece of bare wire that you will need to “lace” through the holes as
shown. Pass 1 1/2 turns through the holes, filling three holes and leaving
a lead coming out at each end. Trim the ends to 1/4“ and bend as
needed for neat installation. Solder it so that it is laying flush with the
board.