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5. Measure the emitter 2 volts negative to the completion voltage.

  • -

    to-base voltage of Q6. A base reading of about

emitter indicates that Q6 is receiving the dash-

6. Ground the base of A reading that shows th the emitter indicates p Replace Q5.

Q2. Measure the base-to-emitter voltage of Q3. e base is about 1 volt negative with respect to roper dash-completion voltage from Q5 to Q3.

7. Ground the base of should cause the tone t

momentarily is working.

grounded. Remove the

Q2.

Momentarily ground the base of Q5:

This

  • o

    go on and stay on until the base of Q4 is

This indicates that the flip-flop multivibrator ground from the base of Q2.

8. Momentarily ground indicates that the comp

the base of Q5. A short-duration tone signal letion circuitry is working.

9. Remove Q1. The ton is reaching Q7.

e should be heard, indicating that the dot signal

10. Measure the base-t the base is about 2 vol that proper dot-complet

o-emitter voltage of Q3. A ts negative with respect to ion voltage is reaching Q3.

reading that shows the emitter indicates Replace Q1.

11. Remove Q3. is working.

Dots should be heard, indicating that the dot generator

12.

Remove

Q6.

Dashes should be heard, indicating that the

multivibrato

rs are all wo

rking.

Replace

Q3

and Q6.

13. Measure

the base-to-

dots positio

n. This volt

negative, in

dicating prop

emitter voltge of Q age should show tha er dot keying.

3, with the paddle at the t the base is about 4 volts

14. Measure The base vol

the base-to- tage should r

emitter voltage of emain positive with

Q6, with the paddle at dots. respect to the emitter.

15. Measure dashes. The bases are ab

the base-to- base voltage out 5 volts n

emitter voltage of s at both Q6 and Q3 egative with respec

Q6, with the paddle at should show that these t to their emitters,

16. Note: waveforms in obtained in response is time to see extremely sh oscilloscope ------------

It may also b

e helpful to

the circuit

description,

refer Simil

your keyer if available. T the trigger p ort. A 10:1 to avoid loa -------------

an oscilloscope wi he oscilloscope mus ulse shown in figur divider probe shoul ding the trigger pu -------------------

to the oscilloscope ar waveforms would be th good low-frequencey t be capable of fast rise- e 14, since this pulse is d be used with the lses with cable capacitance. ----------------------------

January 24, 1975

HD-10

Bulletin No:

Keyer

HD-10-2

Improper Grounding

When servicing a keyer that is inoperative, check for proper grounding at:

  • 1.

    The on-off switch.

  • 2.

    The two ground lugs on the chassis rear panel.

  • 3.

    The phone jack on chassis rear panel.

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