Tektronix 502 series, Инструкция по эксплуатации

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Troubleshooting The CRT Circuit
For
troubles which affect both beams
The intensity, calibration, focus, and geometry
of the crt display depend on the proper opera­
tion of the high-voltage power supply in the CRT
Circuit. In general, troubles occuring in the high-
voltage power supply will produce similar effects
on both beams.
If no high voltage (or insufficient high voltage)
is available from either the grid or cathode sup­
plies, a defective oscillator circuit or excessive
loading is probably the cause. The oscillator can
be quickly checked by placing a neon bulb in
the field of the high voltage transformer T801.
If the bulb glows, the oscillator is operating and
the trouble is likely to be in the secondary wind­
ings of T801 if there is no high voltage, or in
the regulator circuit (V814) if the high voltage is
abnormally low. It is unlikely that both rectifier
tubes would simultaneously be defective.
If the neon bulb does not glow in the trans­
former field, the oscillator is not operating. If
replacement of the oscillator tube V800 and the
regulator tube V814 does not clear up the
trouble, check the compenents of the oscillator
circuit including the primary and secondary
windings of transformer T801.
If the proper output voltage is obtained from
at least one of the high voltage supplies, the os­
cillator circuit need not be checked. In this case,
you can check the rectifier and components
associated with the inoperative supply. If the
proper output voltages are obtained from both
power supplies and the circuit is still not operat­
ing correctly, check the voltage dividers which
control the intensity and focus of the beams. If
these are also normal, the trouble will likely be
the crt itself or its cathode circuit. Badly mis-
focused and distorted displays can be caused by
Fig. 5 -5. Checking operation of the high voltage oscil­
lator circuit by means of a neon bulb placed in the
field of the high voltage transformer.
an open GEOM ADJ control or a loose connec­
tion at the neck of the crt.
If the high voltage appears to be abnormal,
as evidenced by decreased or increased hori­
zontal and vertical deflection sensitivity, the re­
gulator circuit (V814) should be checked. If this
tube or any component of this circuit is changed,
the setting of the HV ADJ control (R824) should
be checked and adjusted if necessary according
to the procedure given in the recalibration sec­
tion of this manual.
For troubles which
affect
only one beam
Troubles which affect only one beam will gen­
erally be caused by defects in the intensity and
focus voltage dividers, by the Astigmatism con­
trols, or by the crt. These parts (except for the
crt) can be checked by voltage and resistance
measurements. If the circuit checks out satis­
factory, replace the crt.
Troubleshooting the V e rtic a l A m p lifie rs
For no spot or trace
As mentioned earlier in the Troubleshooting
Procedure, if a trace (or spot) is visable when the
vertical deflection plates are externally shorted
together, but disappears when the short is re­
moved the vertical amplifier is in a state of dc
unbalance. To determine the cause of this condi­
tion, short the plates of the output stage (V474B
and V484B) together. If the trace does not ap-
MAINTENANCE — TYPE 502
5-9