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Summary of Contents for Heathkit HD-10
- Page 1 HEATHKIT ELECTRONIC KEYER HD-10...
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Page 2: Block Diagram
CIRCUIT DESCRIPTION SCHEMATIC DIAGRAM primary winding of power transformer T1. Re- sistor R8 drops the line voltage that is applied The letter-number designations on the Sche- to the neon pilot lamp, which indicates when matic Diagram are used to identify resistors, the keyer is on. - Page 3 plied to the base of transistor Q3. The negative This positive rise is coupled through capacitor voltage at the base turns Q3 off. This removes C20 to the base of Q1. This drives the base of the positive bias voltage at the base of transis- Q1 to collector cutoff.
- Page 4 Q1 conducting to saturation and turning off Q2. The circuit then reaches its second inactive (quiescent) condition. Capacitor C1 having pre- viously been charged, now discharges at a time constant determined by the value of C10 and control R11. As long as the key lever is held in the dot position, the dot generator multivibra- tor continues to run free.
- Page 5 A positive pulse on the base of Q5 will turn it off, causing its collector current to decrease and its collector voltage to become more nega- tive. This increase in negative voltage at the collector of Q5 is coupled through resistor R51 to the base of Q4 to turn it on.
- Page 6 from Q2 will be a negative going pulse, as Q2 The result of these two signals at he base of turns off. This negative pulse from Q2 has no Q8 is the waveform shown in Figure 17. effect on the flip-flop multivibrator, as only pos- itive going pulses can reset it.
- Page 7 mined by the time constant of resistors R90 If desired, the receiver output may be con- and R100, with capacitors C90 and C100. nected between GND and the Receiver Audio terminals. This allows the audio to be heard in The output signals from the collectors of Q9 headphones connected to the Phone jack of and Q10 are fed to the primary winding of the Electronic Keyer.
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