Tektronix 585 - Page 54

Maintenance — Type 585
A second check is then to set the Type 84 DISPLAY SE 
LECTOR switch to EXT. INPUT and patch into the EXT. INPUT
connector .2 VOLTS of Calibrator signal. It will be necessary
now to turn the Type 585 STABILITY control into the trigger 
able region and adjust the TRIGGERING LEVEL control
for a stable display.
If either of the tests made so far does not produce a dis
play as described, turn to the section on troubleshooting
the vertical amplifier. If the first test above does not pro 
duce two traces, (but the second test permits a proper dis 
play of the Calibrator waveform), check the Time-Base
Generator dual-trace sync pulse source, and step 24 of the
Calibration Procedure. If no Calibrator waveform appears
in the second test, turn to Troubleshooting the AMPLITUDE
CALIBRATOR.
Additional troubles are discussed below in relation to
using a TU-3 or Type 80 Plug-In Unit for this initial trouble
test.
If you are using a TU-3 Test-Load Plug-In Unit set the
INPUT SELECTOR toggle switch to the SIGNAL position and
the oscilloscope AMPLITUDE CALIBRATOR switch to the .2
VOLTS position. (If using a Type 80 Plug-In, set the AMPLI 
TUDE CALIBRATOR switch to .2 VOLTS, and apply the CAL.
OUT signal to the P80 Probe.)
Using a patch cord which introduces no attenuation, con 
nect the CAL. OUT connector to the INPUT connector of the
TU-3 Plug-In. Advance the INTENSITY control to mid-range,
or to the position where a trace normally appears.
If no spot is evident check the Beam-Position Indicator
lamps. If the spot is off the screen vertically turn the VERTI 
CAL POSITION control from one extreme position to the
other, watching the face of the c rt as you do so. If the spot
does not appear, and operation of the VERTICAL POSITION
control has no effect on the Beam-Position Indicator lamps
turn to the section on Troubleshooting the Vertical Amplifier.
If the display which appears consists only of a horizontal
line, you may check the operation of the calibrator by dis
connecting the end of the patch cord from the CAL. OUT
connector and grasping the end between your fingers. A
series of sloping vertical lines (power line pickup) appearing
on the c rt indicates that the Vertical Amplifier is operating
and that the AMPLITUDE CALIBRATOR is probably inopera 
tive. See the section on Troubleshooting the AMPLITUDE
CALIBRATOR for the remedy.
Fig. 5-12. 27-ohm shorting resistor. Part Number 003-002.
If the operation of the VERTICAL POSITION control causes
the vertical Beam-Position Indicator lamps to indicate the
display can be centered vertically, rotate the HORIZONTAL
POSITION control from one extreme position to the other.
If the horizontal Beam-Position Indicator lamps indicate the
display remains off screen refer to the section on Trouble 
shooting the Horizontal Amplifier.
If both sets of Beam-Position lamps indicate that the dis
play is centered, but no display is observed, CAUTIOUSLY
advance the INTENSITY control. Watch for a display to
appear on the screen. If no display is seen or if the display
is of low intensity or defocused but otherwise normal, refer
to the section on Troubleshooting the CRT Circuit.
TROUBLESHOOTING THE VERTICAL AMPLIFIER
No Spot or Trace Visible on CRT
If all power supply voltages are normal, and the crt is
known to be good, failure to obtain a spot or trace on the
screen will be due to improper deflection-plate voltages. This
condition is caused by a d c unbalance in either or both of
the deflection amplifier circuits or by a loose c rt lead.
To determine which circuit is at fault, adjust the Time-
Base A controls for a free-running sweep at 1 MILLISEC/CM
(STABILITY control fully clockwise) and set the INTENSITY
control to midrange. Using a screwdriver with an insulated
handle, CAREFULLY short the vertical deflection plates to 
gether at the neck pins on the c rt. These are the pins marked
BLUE (UPPER) and BROWN (LOWER). Be careful not to
short either pin to the metal shield around the c rt. If the d c
unbalance is being produced in the vertical deflection circuit
the trace will appear at or near the center of the c rt when
the vertical deflection plates are shorted together. If the
trace does not appear, however, the trouble does not lie
in the vertical circuit and the d c balance of the horizontal
circuit can be checked in a like manner after first stopping
the sweep.
If it is determined that the vertical deflection circuit is un 
balanced, the next step is to check the system for the fault.
This is accomplished in a manner similar to the shorting
procedure used to find the c rt electrical center. It is best
to guard against common-mode oscillations by performing
the shorting operation using a 27  1-watt resistor. Figure
5-12 illustrates a satisfactory method of holding the short 
ing resistor for use in the following procedure.
1. Use the shorting resistor to short the grids of V 1 284,
located on a two-terminal ceramic strip at its socket.
If the trace appears, V 1 284 and circuit is good.
2. Connect the shorting resistor between the grid lines of
the Output Stage near V 1 214. The grid lines are wound
with green colored wire. If the trace appears, all tubes
and circuitry from this point to the c rt are good.
3. Connect the shorting resistor between the plate lines of
the Delay-Line Driver stage. The plate lines are wound
with red wire. If the trace appears, the Delay Line is
not open.
4. Connect the shorting resistor between the grid lines of
the Delay-Line Driver stage. If the trace appears, the
5-8