-11-
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
V
Amps
COM
V/
W
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
Summary of Contents for SUPERHET AM-550TK
Page 31: ... 30 SCHEMATIC DIAGRAM ...
