Tektronix 585 - Page 51

Maintenance — Type 585
used in the assembly of the Type 585 Oscilloscope. These
parts are manufactured or selected by Tektronix to satisfy
particular requirements or are manufactured specially for
Tektronix by other companies in accordance with Tektronix
specifications. These parts and most mechanical parts should
be ordered directly from Tektronix. They are normally dif 
ficult or impossible to obtain from other sources. All parts
may be obtained through your area Tektronix Field Engi 
neer or Field Office.
TROUBLESHOOTING
Troubleshooting Procedure
This section of the manual contains information for trouble 
shooting the Type 585 Oscilloscope. Before attempting to
troubleshoot the instrument, however, make sure that any
apparent trouble is actually due to a malfunction within
the instrument and not to improper control settings or to a
faulty plug-in unit or probe. Instructions for the operation
of the Type 585 and general information concerning plug-in
operation, are contained in the Operating Instructions sec 
tion of this manual. Operating instructions for a specific
plug-in unit or probe will be found in the manual for that
unit.
When vertical system troubles exist, to determine that the
oscilloscope is at fault, the plug-in unit may be replaced
with another known to be in good operating condition. If
the trouble is still apparent, it is almost a certainty that the
oscilloscope is at fault. However, should the trouble appear
to have been corrected by replacing the plug-in unit, the
trouble most likely lies within the original plug-in unit and
not the oscilloscope.
Tube failure is the most prevalent cause of circuit failure.
For this reason, the first step in troubleshooting any circuit
in the instrument is to check for defective tubes, first by
looking for dark heaters, and then replacement by direct
substitution. Do not depend on tube testers to indicate the
suitability of a tube for certain positions within the instru 
ment. The criterion for usability of a tube is whether or not
it works satisfactorily. Be sure to return all good tubes to
their original sockets; if this procedure is followed less re 
calibration of the instrument will be required upon comple 
tion of the servicing.
When replacing any tube in the instrument, check first to
see that components through which the tube draws current
have not been damaged. Shorted tubes will sometimes over 
load and damage components. These can generally be
located by visual inspection. If no damaged components are
apparent, and if tube replacement does not restore opera 
tion, it will be necessary to make measurements or other
checks within the circuit to locate the trouble.
The component number of each electrical part is shown
on the circuit diagrams. The following chart lists the com 
ponent numbers associated with each circuit.
All numbers
less than 100 ............... Time-Base Trigger A and B
All 100 numbers ........... Time-Base Generator A and
Timing Switch A
All 200 numbers ........... Time-Base Generator B and
Timing Switch B
All 300 numbers ...........
All
400 numbers ...........
All
600 and
700
num
bers .................
All
800 numbers ...........
All
1000
numbers .........
All
1100 numbers ..........
All
1200 numbers .........
All
8000 numbers .........
Horizontal Amplifier and Ex 
ternal Horizontal Amplifier
Delay Pickoff
Low-Voltage Power Supply,
and Regulated Heater Supply
CRT Circuit and High-Voltage,
plus Amplitude Calibrator
Vertical Amplifier Delay-Line
Driver
Power supply decoupling net 
works for vertical amplifier
and plug-ins
Vertical Amplifier Output
Stage
Type 80 Plug-In Unit and
P80 Probe
Switch wafers shown on the schematic diagrams are coded
to indicate the position of the wafer on the switches. The
number portion of the code refers to the wafer number on
the switch assembly. Wafers are numbered from the front
of the switch to the rear. The letters F and R indicate
whether the front or the rear of the wafer is used to per 
form the particular switching function.
CIRCUIT TROUBLESHOOTING
Although the Type 585 is a complex instrument, it can be
thought of as consisting of nine main circuits, in addition to
the Calibrator circuit. These are the:
1. Low-Voltage Power Supply
2. CRT Circuit and High-Voltage ’ Power Supply
3. Vertical Amplifier and Delay Line
4. Time-Base Trigger Circuit A
5. Time-Base Trigger Circuit B
6. Time-Base Generator A
7. Time-Base Generator B
8. Delay Pickoff
9. Horizontal Amplifier
The first circuit to check, for practically any type of
trouble, is the Low-Voltage Power Supply. Because of the
circuit configurations employed, it is possible for an improper
power supply voltage to affect one circuit more than the
others. For example, if the gain of the Vertical Amplifier
should decrease slightly, while the other circuits appear to
be functioning normally, this could be due to an improper
supply voltage and not to any condition originating in the
Vertical Amplifier. In cases of this type, valuable time can
be saved by checking the power supply voltages first.
On the other hand, the crt display can often be used to
isolate trouble to one particular circuit when trouble exists
in that circuit. If there is no vertical deflecton, for example,
when the intensity and horizontal deflection appear to be
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