Heathkit IO-4550 - Page 32

Page 30
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Figure 20
Adjust the X-Y CAL control (R258, on the horizontal
circuit board) to place the two dots exactly 5 cm apart
as shown in Figure 20.
Disconnect the Y1 test cable from the 1V P-P
connector.
CHOPPED BLANKING
Turn the TIME/CM switch fully counterclockwise to
the EXT position.
Use the Y1, Y2, and HORIZ POSITION controls and
Position the dots as shown in Figure 20A or 20B.
If the dots look like those in Figure 20A, proceed to
“Attenuator Compensation.”
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Figure 20B
If the dots look like these in Figure 20B (connected
together), turn CHOP BLANK ADJ control R428 until the
dots look like those in Figure 20A. Then proceed to
“Attenuator Compensation.”
ATTENUATOR COMPENSATION
The purpose of the following adjustments is to obtain the
Proper amount of high frequency compensation for each
Position of the VOLTS/CM switch. Parts A, B, and C of
Figure 21 show the conditions of too much compensation,
too little compensation, and the correct amount of
compensation respectively. Use a plastic alignment tool to
make the following adjustments.
1. Set the indicated front panel controls as follows:
TIME/CM .2mS
TRIG Y1,+
Y1:
INPUT switch AC
VARIABLE Fully clockwise (CAL)
VOLTS/CM 100 mV
POSITION Center trace on screen