Heathkit IO-4550 - Page 41

C
Gagurmarruire
PROBLEM POSSIBLE CAUSE
Oscilloscope does not 1. Check pins 14 and 15
blank (retrace visible), of IC203A for blanking
or does not unblank signal.
(no trace). 2. Check holes H and F
on the high voltage
circuit board for the
blanking signal. CAUTION:
The blanking circuit
operates at 1700 volts
below ground potential.
If you suspect a defective
component, remove and
check the component.
Do not check it on the
circuit board. If your
probe slips, a number
of components could be
damaged.
1. Check Q209, IC208, and
associated circuitry.
Calibrator does not
function.
1. Adjust X-Y CAL control
R258.
X-Y not calibrated.
1. Go to Test Chart #12.
No “X" and/or “Y”
position control in X-Y.
1. Go to Test Chart #12.
Oscilloscope will not
unblank in X-Y, unblanks
in normal operation.
1. Check Q207, Q208, and
associated circuitry.
No “X" deflection in
External X operation.
1. Check for normal “Y“’
channel operation.
No “Y” deflection in
External X operation.
Check for chop signal
at pin 8 of 1C211.
2. Check Q120, Q121, and
associated circuitry.
Check diode switch.
Only one “’Y” channel
functions in External
X operation.
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