they should be used for reference only, and
are not meant to serve as a " check list"
or sequence chart for circuit testing. This sys
tem might eventually lead to the trouble, but
the isolation or signal tracing methods are gen
erally much faster.
Many troubles can be localized by observing
the waveforms at various points in the cir
cuits with the instrument’
s own cathode-ray
tube. Another oscilloscope may be used if avail
able. This method is explained in detail under
servicing instructions for each chassis.
Since a large percentage of troubles experi
enced will likely be caused by defective tubes, it
is advisable to check the tubes in the suspected
circuits before carrying out extensive tests of
other components. Tube testing is best accom
plished by the substitution of another one known
to be good. A tube tester is useful, but it
may not indicate some defects which cause mal
functioning in the oscilloscope. If the tube
defect has been caused by an abnormal cir
cuit condition, this should be corrected before
replacement is made. Although specially
matched or selected tubes are not required in
the Type 511 A, some individual tubes which
perform normally in less critical circuits
may not function well in certain circuits of
this instrument. Specific conditions are dealt
with under the individual chassis headings. An
accurate voltmeter having 20,,000 ohms per volt
or greater sensitivity, an accurate ohmmeter,
spare tubes, and simple tools should be available.
CAUTION--WHEN ANY PART WHICH AF
FECTS THE ADJUSTMENTS OR CALI
BRATION OF THE TYPE 511A IS RE
PLACED, THE AFFECTED CIRCUITS
SHOULD BE READJUSTED AS EX
PLAINED IN THE ADJUSTMENT SEC
TION.
Absence of Power
When this condition is due to a blown fuse,
check line voltage and, if normal, replace the
fuse (3 amp, slo-blo), throw the power switch
on, and check for any abnormal condition which
may have caused the fuse to blow. If a short
circuit or overload exists, the length of time
required to blow the fuse should provide an
indication of the trouble. For example, a delay
until the high voltage rectifiers begin to conduct
would indicate trouble in the DC supplies or
the circuits fed by them. This condition may be
isolated by removing the high voltage rectifier
tubes, V21, V22, V23 and V24 (including V25,
S/N101-454); and replacing first (V25, S/N101-
454) V24, then V22 and V23, and finally V21, al
lowing several minutes operation between each
replacement. After the faulty DC supply is lo
cated, disconnect it at the power supply terminal
strip, then at the video amplifier terminal strip,
to further isolate the defect. See the schematic
diagrams for average currents.
A five-second delay before the fuse blows
might be caused by a short in the tube-heater
circuits, and should also be isolated by dis
connecting at the terminal strips. A delay of
one second or less would suggest a short cir
cuit on a high voltage secondary of Tl.
Absence of Spot on Cathode-Ray Tube
To determine whether this is due to absence
of the electron beam or to the beam being de
flected off the fluorescent screen, connect to
gether and ground all four CRT deflection plates
at the access panel. If a centered spot now
appears, abnormal deflection plate potentials
are indicated. Remove the short circuiting con
nections. With the VERT. POSITION control
centered, the HOR. POSITION control clock
wise, the SWEEP STABILITY control counter
clockwise, and no vertical input signal, measure
the voltage between each CRT deflection plate
and ground, which should be within +or-60
volts. The
a v e r a g e
potential of both horizontal
(X) plates, or both vertical (Y) plates, should
be or-40 volts of ground when measured
under the above conditions. Abnormal potential
on the horizontal plates indicates malfunctioning
of the sweep amplifier or associated circuits;
and on the vertical plates, a defective positioning
circuit or shorted coupling capacitor.
If the deflection plate voltages are normal,
check the CRT connections, and observe the
CRT heater by viewing it through the small
hole in the upper rear part of the CRT shield.
Next, measure the power-supply output voltages,
the CRT bias (pin 2 to pin 3), the first anode
(pin 5) and the second anode (pin 9) voltages.
If these readings are normal, replacement of
the CRT is indicated.
Power Supply
1. If the output voltage of one of the regulated
T Y P E 5 1 1 - M A I N T E N A N C E
P A G E 4 - 3
Summary of Contents for 511
Page 1: ......
Page 4: ......
Page 5: ......
Page 26: ......
Page 52: ......
Page 58: ...Fig 5 6 Interior view right front side S N 845 1405 TYPE 511 A 511 AD SECTION 4 PAGE 22 ...
Page 60: ......
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Page 62: ......
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Page 66: ...Fig 5 14 Video Amplifier top S N845 1459 Fig 5 15 Video Amplifier bottom S N845 1459 ...
Page 68: ...Fig 5 18 Power Supply bottom view S N 845 1629 Fig 5 19 P ow er Supply top view S N 845 1629 ...
Page 72: ...DEGREES OF PHASE SHIFT Fig 5 27 SN 845 and up TEKTRONIX INC 12 28 50 ...
Page 97: ......
Page 98: ......
Page 101: ...AA ...
Page 102: ...SWEEP MAGNIFIER SWEEP AMPLIFIER c r r c r r s c ...
Page 105: ...TYPE 5IIAD CATHODE RAY OSCILLOSCOPE S N 2406 4 UP A A ...
Page 106: ... 2 2 5 V VERTICAL AMPLIFIER ...
Page 107: ...TYPE 511 CATHODE RAY OSCILLOSCOPE S N 101 454 AA POWER SUPPLY ...
Page 108: ...TO S7 3 A 6 6 117 V 60 APR 1949 S N 455 2405 A A ...
Page 111: ...4 A A C n o c n n r ...
Page 113: ......