Tektronix 507, Инструкция по эксплуатации

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THE POWER CIRCUITS ENERGIZED, THE UT­
MOST CAUTION MUST BE OBSERVED. BOTH
THE +750-VOLT AND THE +475-VOLT SUP­
PLIES ARE POTENTIALLY MORE DANGEROUS
THAN THE 4-KV AND 20-KV SUPPLIES. THE
+750-VOLT AND THE +475-VOLT SUPPLIES
HAVE MUCH LOWER INTERNAL IMPEDANCE.
USE ONLY INSULATED TOOLS. STAND ON A
DRY FLOOR AND DO NOT LEAN WITH THE
BARE ARMS ON THE FRAMEWORK OF THE IN­
STRUMENT. IF POSSIBLE, KEEP ONE HAND IN
YOUR POCKET.
Fuses
The fuses located on the front panel of the
power supply provide over-current protection.
If the DC SUPPLIES fuse blows, the first step in
locating the trouble should be to determine
whether the trouble is in the power unit or the
indicator unit. This can be determined by dis­
connecting the inter-unit power cable. If a new
fuse blows with the cable disconnected, the
trouble is in the power unit and the usual types
of checks for capacitor failure and tube shorts
should be made until the trouble is isolated.
If the fuse does not blow except when the in-
ter-unit cable is connected, however, the trouble
is likely to be found in the indicator unit. In this
case, first measure the resistance to ground at
each dc voltage bus to determine if any are be­
low 15,000 ohms. The dc voltage buses can be
located at the plugs which connect to the inter­
unit cable as follows:
Pin 1 +750 volts
Pin 2 +475 volts
Pin 3 -f-360-volf unregulated
Pin 4 +225-volts
Pin 8 -—250 volts
If no low-resistance circuits are found to exist,
it is possible there is a type of tube short that
occurs only when both heater and plate volatges
are applied. By lifting individual bus wires from
the power plug in the indicator unit, and turning
the power on the offending circuit can be
isolated to one drawing current from one of the
regulated supplies. Then, by tracing the color-
coded bus wire, or by referring to the circuit dia­
gram, the circuits drawing current from this
supply can be determined and you can then
troubleshoot in these circuits until the one at
fault is identified.
If the regulated voltages are off in value, look
for trouble in the power supply. If all voltages
are off in value look for trouble in the —250-
volt supply to which all other supplies are com­
pared. If all voltages are low V612 may be low
in emission or V619 may not be conducting. If
all voltages are high V619 may be shorted, in
which case the —250-volt bus should indicate
about —350 volts.
If individual voltages are off check the volt­
age at the plate of the series regulator tube
involved for evidence of low cathode emission.
Check the resistance and voltage at the grid of
the reference tube for evidence of failure in
the voltage divider.
Sweep
If a spot can be made to appear at left center
under normal operating conditions, but no sweep
occurs advance the STABILITY control full clock­
wise. If a sweep occurs with this control adjust­
ment, the difficulty may be in the trigger circuit.
Turn the TRIGGER SELECTOR to MARKER and
the SIGNAL MODE switch to INTERNAL MARK­
ER; then back off on the STABILITY control and
attempt to trigger the sweep rather than permit
it to free run. If the sweep can be triggered by
the internal marker, but you were not able to
trigger the sweep with an external trigger or by
the signal, then check for failure of the divider
at the SIGNAL IN or EXTERNAL TRIGGER INPUT
connectors.
If the sweep can not be triggered by the mark­
er generator, measure the amplitude of the multi­
vibrator waveform at the cathode of V243A
with another oscilloscope.
The peak-to-peak
amplitude of the multivibrator waveform (not
that of the superimposed markers) should be
about 5 volts at this point. If adequate output is
obtained, look for low gain in the trigger ampli­
fier.
Cathode-Ray Tube Power Supply
In case of failure of the 20-kv power supply,
determine whether the oscillators supplying ac
input voltage to the high-voltage and filament
supplies are functioning properly. This can be
determined by measuring the dc grid voltages of
the two oscillator tubes using 20,000-0/v meter.
The voltage at the grid of V820 should be about
—27 volts, and the voltage at the grid of V830
should be about —23 volts. Or alternately, the
ac voltages may be observed on another oscil­
loscope.
If it is determined that failure has not occured
in the oscillator circuits, it is recommended that
your Tektronix field engineer be consulted in
regard to repair of the supply in the nearest
Tektronix field maintenance office.
3-2
MAINTENANCE — TYPE 50 7 ®