Input Bias - Elenco Electronics AM-550CK Assembly And Instruction Manual

OUTPUT BIAS TEST
Adjust your VOM to read 9 volts DC 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 4.5 to 5.5 volts.
If you get this reading, go on to the next test. If your
GND
TP10
TRANSISTOR BIAS TEST
Move the positive lead of your VOM to test point 7 (TP7).
Make sure that the power is ON. The voltage should be
between 0.5 and 0.8V higher than the voltage at TP8.
All silicon transistors biased for conduction will have

INPUT BIAS

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 Q6. If your circuit passes this
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.
Figure 5
approximately 0.7V 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.
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.
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