Elenco Electronics AM-550TK Instruction Manual download pdf (Page 12)

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Adjust your VOM to read 9 volts and connect it to test

point 8 (TP8) as shown in Figure 5.

Make sure that the battery, or a 9 volt power supply (if

available), is properly connected and turn the power

ON. The voltage at TP8 should be between 4 to 5 volts.

If you get this reading, go on to the next test. If your

circuit fails this test, turn the power OFF and check that

all of the transistors are correctly inserted in the correct

locations. The E on the transistor indicates the emitter

lead and should always be in the hole with the arrow.

Check that resistors R13 and R14 are the correct

values and not interchanged.

OUTPUT BIAS TEST

Figure 5

Amps COM V/Ω

Battery

GND

R15

Move the positive lead of your VOM to test point 7

(TP7). Make sure that the power is ON. The voltage

should be between .5 and .8V higher than the voltage

at TP8. All silicon transistors biased for conduction will

have approximately .7V from the base to the emitter. If

your circuit fails this test, turn off the power and check

that Q6 is properly inserted into the circuit board.

TRANSISTOR BIAS TEST

Move the positive lead of the VOM to test point 6 (TP6).

Make sure that the power is ON. The voltage at TP6

should be very close to the voltage at TP7. This is true

because very little DC current flows through resistor

R16 making the voltage at the emitter of Q4 very close

to the voltage at the emitter of Q5. If your circuit passes

this test, leave the VOM connected and go to test 1 in

the Dynamic Measurements Section. If your circuit fails

this test, turn the power OFF and check transistors Q4,

Q7 and resistor R16. All static tests must pass before

proceeding to the Dynamic Tests or the next section.

INPUT BIAS

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 31 32

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Elenco Electronics AM-550TK Instruction Manual Page 12