Heathkit IO-4550 - Page 40

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38
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SSS)
PROBLEM POSSIBLE CAUSE
Excessive overshoot. 1. Adjust high frequency
compensation C118 — (1 or 2).
“Hash” or “grass’’ appears at . 1. Check for chop signal
low sweep speeds in dual at pin 6 of IC210B.
trace operation. 2. Check 0401, ZD401, and
associated circuitry. CAUTION:
These components are on the
high voltage circuit board.
Oscilloscope does not sweep. 1. Go to Test Chart #10.
1. Adjust DC trigger
ZERO control R149-(1 or 2).
2. Goto Test Chart #9.
Oscilloscope sweeps but
does not trigger properly.
Oscilloscope triggers but
auto-baseline does not function.
Check IC205 and
associated circuitry.
Check I1C209.
Sweep out of calibration. 1. Calibrate sweep.
Sweep will not calibrate. 1. Check high voltage
(—1700 VDC).
Go to Test Chart #10.
Sweep
is
nonlinear.
Check
Q203,
0204,
Q205,
0206,
and associated circuitry.
Time base ranges do
not change in proper
order.
Check TIME/CM switch
and associated RC
networks.
Trace too long or too
short, Oscilloscope
calibrated.
Perform the ‘Touch-Up
Adjustments” in the
“Calibration” section.
Some retrace appears when operating
in the high Time/Cm settings when
not triggered (auto base line). When
triggered on a waveform, no retrace
is visible.
This is normal.