Heathkit IO-4550 - Page 29

VERTICAL AMPLIFIER BALANCE
NOTE: During the following steps, you may experience the
rare situation that the vertical amplifier of one channel will
not balance properly. If this happens, interchange transistors
Q101 and Q102 of the channel that does not balance. The
transistor leads are not soldered to the socket pins.
Channel Y1: Perform the following numbered steps 1-11.
Adjust only the controls associated with Channel Y1.
1. Adjust the POSITION control to place the trace on
the horizontal centerline.
2. Turn the VARIABLE control fully counterclockwise.
The trace may move off the screen.
3. Adjust the POSITION control to return the trace to
the center horizontal graticule line.
4. Turn the VARIABLE fully clockwise (CAL).
5. Slowly adjust the DC BAL control (a screwdriver
adjustment through the front panel) to return the
trace to the center horizontal graticule line.
6. Repeat steps 2 through 5 until the trace does not
move when you turn the VARIABLE control. Leave
the VARIABLE control in the fully clockwise position
(CAL).
7. Turnthe VOLTS/CM switch to the 10mV position.
8. Adjust the BAL control [R124, on the vertical circuit
board (see Figure 16)]to return the trace to the center
horizontal graticule line.
9. Turn the VOLTS/CM switch back and forth between
the 10mV position and the 50mV position and adjust
the BAL control so the trace does not move when the
switch is turned from one position to the other.
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10. Repeat steps 2 through 5.
11. Turn the Y1 POSITION control fully
counterclockwise (OFF). Then turn the Y2 POSITION
control clockwise and center the trace on the screen.
Channel Y2: Perform the previous numbered steps 1-10.
Adjust only the controls associated with Channel Y2.
TRIGGER
1. Set the Y1 and Y2 INPUT switches to GND.
2. Adjust the Y1 and Y2 POSITION controls to place
both traces on the horizontal centerline.
3. Adjust your voltmeter to measure —3.0 volts DC.
4. Connect the common voltmeter lead to the
Oscilloscope chassis.
5. Measure the voltage at TP14 (test point 14) on the
vertical circuit board. (See Figure 16 in the
“Illustration Booklet.’’) Adjust the Y1 ZERO control
(R149-1, on the vertical circuit board) for zero volts.
6. Measure the voltage at TP15 on the vertical circuit
board. Adjust the Y2 ZERO control (R149-2, on the
vertical circuit board) for zero volts.
7. Disconnect the voltmeter.