IBM 5081 Model 19 Display Maintenance Information

Figure 1 - Front view.	Figure 2 - Rear view.	Figure 3 - Top view.	Figure 4 - Right side view.	Figure 5 - Left side view.
Figure 6 - Rear view (interior).	Figure 7 - H and V convergence sequence.	Figure 8 - Deflection "D" PCB.	Figure 9 - Deflection "D" PCB in open position (component side).	Figure 10 - Convergence "L" PCB.
Figure 11 - Convergence "L1" PCB in service position.	Figure 12 - High voltage power assembly.	Figure 13 - CRT/yoke assembly.	Figure 14 - Control panel.	Figure 15 - Connector reference for continuity and voltage checks.

DANGER

Most printed circuit boards (PCBs) contain voltages in excess of 42 volts and must not be operated in the service position (except the "D" and "LI" PCBs). All exposed PCBs are provided with plastic safety shields over the wiring side. These shields MUST NOT be removed for alignment purposes. The "L1" PCB does not have voltages in excess of 42 volts present. Access holes are provided through the shields for adjustments. An exception to this is the convergence "LI" PCB which is adequately shielded internally and may be placed in the service position for convenience of convergence adjustment. The "D" PCB may be placed in the service position to allow access to the HVPS and the CRT neck components.

Warning: Do not turn 5081 power on with any connectors unplugged from any PCBs unless specifically directed in the procedure.

 
The alignment procedures assume that a field replaceable unit (FRU) has 
been replaced in the 5081 and a complete realignment is required. The 
prerequisites and preliminary adjustments must be read and followed 
before any alignments are made (see 3.1, "Prerequisites" and 3.2, 
"Preliminary Adjustments"). Then read each alignment 
procedure before making any adjustments. 
 
The alignment procedures are sequential. Deviation from this sequence 
will yield undesirable results. 
 
Upon completion of the alignment procedures, verify proper operation of 
the 5081 by following the steps under 4.8, "Verification". 
 
3.1 Prerequisites 
 
Turn the 5081 power on and allow at least 30 minutes for warm-up, with 
the covers on, before making adjustments. If the 5081 is not allowed to 
warm-up for 30 minutes, correct adjustments cannot be made and 
this may result in a follow-up service call. 
 
  	The 5081 must be connected via coaxial cable to a device that 
provides a 60 Hz refresh rate video (red, green, blue) signal. 
 
   The brightness potentiometer on the front panel must be set fully 
clockwise. 
 
  	The horizontal and vertical convergence potentiometers, and 
vertical centering potentiometer on the front panel must be in their 
center detent positions. 
 
  	The voltage selector switch must be set to the correct voltage 
setting (100 120/220- 240 Vac). 
 
Chapter 3. Alignment Procedures  3-1 
 
  	The three-position switch, located in the upper left comer of the 
"A" PCB, must be in its NORM (center) position. 
 
  	Two green wire jumpers on the "D" PCB must be plugged into the "N" 
position. Position "W" is not used. Remove power before opening the "D" 
PCB. Jumpers are below connectors DY 1 and DY2. Refer to figure 6-11. 
 
Secure the PCB with screws before applying power. 
 
  	Display the color bar pattem. Check the locations of the red, 
green, and blue color bars, as displayed on the screen, to ensure proper 
video cable connections.

3-2	5081 Model 19 MIM 
 
 
 
3.2 Preliminary Adjustments These steps must be followed in sequence. 
 
Reference to the adjustment sequence follows each step heading in the 
following format: Example, (D1) where D = the "D" PCB and 1 = the 
potentiometcr number. 
 
  	Remove the cover by removing the four (4) retaining screws at the 
rear of the 5081. 
   Remove the EMC shield by removing the four (4) retaining screws. 
 
  	A 5081 adjustment tool can be found in a snap-fastener on the top 
of the EMC shield. REPLACE THE TOOL IN ITS HOLDER WHEN PROCEDURE IS 
COMPLETE. 
 
   Display the color bar test pattern 
 
3.2.1 Low-voltage Power Supply 
Warning:  The low-voltage power supply is factory preset. Do not attempt 
to readjust or repair the low-voltage power supply. 
 
Using a DVM, measure the following voltages: 
 
VOLTS    TOLERANCE   CHECK PIN 
 
+ 12 Vdc	:k O. 5 Vdc 
- 12 Vdc	:k O. 5 Vdc 
+ 60 Vdc	+ 8.0 - 5.0 Vdc 
+ 145 Vdc	+ 3.0 Vdc 
 
Connector DI-4 Connector DI-6 Connector DI-2 Connector D 1 - 1 
 
If voltages are not within tolerance or are missing, an obvious symptom 
should be apparent. Refer to the 5081 Symptom Index. 
 
3.2.2 High-voltage Power Supply Warning:  The high-voltage power supply 
is factory preset. No attempt shall be made to readjust or repair the 
high-voltage power supply. 
 
3.2.3 Horizontal Frequency (D1 H-FREQ) Disconnect the green coaxial 
signal cable at the I/0 panel. With the brightness override button 
pressed, adjust the horizontal frequency (D1) control for a near stable 
image. The display will drift left and right with the green coaxial 
signal cable disconnected. Reconnect the green coaxial signal cable and 
observe that the 5081 synchrorazes immediately. 
 
To check stability of horizontal synchronization: 
 
1.	Disconnect the green coaxial signal cable for 5 seconds, then 
reconnect. The 5081 must synchronize immediately. If the 5081 does not 
synchronize or is slow, re-adjust the horizontal frequency D1 control. 
 
Chapter 3. Alignment Procedures  3-3 
 
3.2.4 3.2.5 
 
3.2.6 3.2.7 
 
2.	Turn the 5081 power off for 5 seconds; then rum the 5081 power on. 
The image will be wavy for the f~rst few seconds, while the CRT is being 
degaused. The 5081 must synchronize immediately after degaussing. 
 
Horizontal Phase (D2 H-PHASE) 
With the brightness override button pressed, adjust horizontal phase 
(D2) until the image is in the center of the raster. 
 
CRT Cutoff 
 
(Screen Potentiometer) 
Note: This adjustment can be made more accurately in dimmed light. The 
image area background within the raster must be black. Set the rightness 
potentiometer, on the front panel, to the full CW position. 
 
Display the Black FIat Field test pattem. Adjust the screen 
potentiometer, located on the high-voltage assembly, clockwise until the 
raster appears, then turn the potentiometer counterclockwise until the 
background just disappears. The black area of the test pattern should 
appear totally black. This is a critical adjustment; a setting too far 
toward black results in loss of maximum brightness. 
 
Brightness Override Test 
Note: This adjustment can be made more accurately in dimmed light. 
 
Press the brightness override button and observe that the raster becomes 
visible. Release the brightness override button. The raster should retum 
to black. 
 
Focus Adjustment 
Note: This adjustment can be made more accurately in dimmed light. 
 
Display the crosshatch pattern. Adjust the focus potentiometer, located 
on the highvoltage assembly, refer to figure 6-14, for the best overall 
definition of the screen image at a point midway between the center and 
a corner of the screen display area. 
 
3-4 508x Model 19 MIM 
 
3.3 
 
Geometric Adjustments 
 
Before proceeding with these steps, follow the steps under 3.1, 
"Prerequisites" and "Preliminary Adjustments. 
 
1. Display the crosshatch pattern 
 
2.	Position the alignment mask (Part Number 6246502) on the front of 
the 5081 with the left and bottom edges aligned with the bezel. Put 
maskhag tape on the cutouts on the left and right sides of the mask to 
hold the mask in position. 
 
Note: To elh'rfinate parallax error during the alignment procedures, 
position yourself so that the viewed point is directly in front of you 
and at eye level. 
 
Note:  If a convergence error exists, it may be helpful to unplug the 
red and blue coax from the I/0 panel until after the geometry 
adjustments are completed. Disconnecting the red and blue coax will 
produce one set of lines in green. 
 
Adjust in the following order: 
 
See Figure 8 for potentiometer locations and sequence 
numbers used on the "D" PCB. 
 
1. HORIZONTAL CENTERING AND SIZE (D3 H-CENT) (D4 H-SIZE) 
 
Adjust the horizontal centering potentiometer (D3) and horizontal size 
potentiometer (D4) so that the left and right sides of the test pattern 
fit within the designated area of the mask. If the lines do not fit 
completely within the boundaries, adjust until the center of the lines 
midway between the ends are within the boundaries of the mask. 
 
Note:	Ignore pincushion and barrel distortion at this time. 
 
2. VERTICAL CENTERING AND SIZE (D5 V-CENT) (D6 V-SIZE) 
 
Adjust the vertical centering potentiometer (D5) and vertical size 
potentiometer (D6) so that the top and the bottom of the test pattern 
fits within the designated area of the mask. If the lines do not fit 
completely within the borders, adjust until the center of the lines 
midway between the ends are within the borders of the mask. 
 
Note: Ignore pincushion and barrel distortion at this time. 
 
3.	VERTICAL PINCUSHION (D7 TOP AMP) (D8 TOP PHASE) (D9 BOT AMP) (D10 
BOT PHASE) 
 
a. TOP PINCUSHION CORRECTION 
 
Inspect the top edge of the displayed pattern for pincushion or barrel 
distortion. Use Top Amp (D7) and Top Phase (DS). Adjust Top Amp (D7) to 
cause a bowed line. Adjust Top Phase (DS) so that the left half 
is symmetrical with the right half. Readjust Top Amp (D7) to obtain a 
straight line. 
 
b. BOTTOM PINCUSHION CORRECTION 
 
Inspect the bottom edge of the displayed pattem for pincushion or barrel 
distortion. Use Bottom Amp (D9) and Bottom Phase (DIO). Adjust 
 
Chapter 3. Alignment Procedures  3-5 
 
Bottom Amp (D9) to cause a bowed line. Adjust Bottom Phase (DIO) so that 
the left half is symmetrical with the right half. Readjust Bottom Amp 
(D9) to obtain a straight line. 
 
4. VERTICAL LINEARITY (DII V-LIN BAL) (D12 V-LIN) 
 
Ensure that the spacing between all horizontal lines is equal. The 
intersection between the horizontal and vertical lines must fall within 
the circle targets of the alignment mask. If it does not, make small 
adjustments to the Vertical Linearity potentiometer (D12). After each 
adjustment use the Vertical Lineafity Balance potentiometer (D11) to 
vertically center the middle horizontal line. Adjust for equal spacing. 
A small refinement of Vertical Size may be required. 
 
5. HORIZONTAL PINCUSHION (D13 PIN AMP) (D14 SIDE PIN BAL) 
 
Inspect both sides of the displayed pattem for pincushion or barrel 
distortion. The left and right vertical edge of the image area must be 
adjusted until lines are straight from the top to bottom comers. Any 
remaining distortion must be free of abrupt discontinuities and 
represent smooth curves. Use Side Pin Balance (D14), and Side Pin Amp 
(D13) to adjust for straight sides. The keystone adjustment in the next 
step will fit the left and right edges into the border of the alignment 
mask. 
 
Notes: 
 
a.	It may be necessary to repeat the adjustment of the potentiometers 
to properly align the sides of the image area. 
 
b.	The Side Pin amp (D13) controls the magnitude of correction. The 
Side Balance (D14) controls the balance of correction on each side. 
 
6. KEYSTONE CORRECTION (D15 KEY) (D16 KEY BAL) 
 
Inspect both sides of the displayed pattem for squareness to top and 
bottom. The left and right edges of the image area must fit within the 
border of the alignment mask. Use Key (D15) and Key Bal (D16) to adjust 
as necessary. 
 
Note: It may be necessary to alternate between adjustments to properly 
align the sides. If the sides are curved, repeat the Horizontal 
Pincushion adjustments in the previous step. 
 
5081 Model 19 MIM 
 
 
 
3.4.1 3.4.2 
 
CRT Neck Components (Checks) 
 
Before proceeding with these steps, follow the steps under 3.1, 
"Prerequisites" and 3.2, "Preliminary Adjustments". 
 
Purity Check 
1. Display the green fiat field pattern. 
 
2. A solid green fiat field should appear, not shaded with red or blue. 
3. Display the red flat field pattern. 
 
4. A solid red flat field should appear, not shaded with green or blue. 
5. Display the white flat field pattern. 
 
6.	A solid white flat field should appear, not shaded with color. A 
small amount of impurity may appear in any comer and must be evaluated 
for acceptability. If purity adjustments are necessary, refer to 
3.4. 1, "Purity Check." 
 
Symmetry Check 
Note: Proper convergence of the 5081 cannot be done if the beam symmetry 
is not correct. 
 
1. With power off, remove cover and EMC shield. 
 
2. Display the crosshatch test pattern. 
 
3. On the "LI" PCB, adjust the center horizontal convergence 
potentiometer (RV23) to separate the red and blue vertical lines from 
the green vertical line at the exact center of the pattern. Separate the 
lines by approximately 1.0 mm. 

4. Adjust the center vertical convergence potentiometer (RV8) to 
separate the red and blue horizontal lines from the green horizontal 
line at the exact center of the pattern. Separate the lines by 
approximately 1.0 min. At the center of the screen, observe that the red 
and blue lines are equally spacedtion'  on either side of the green 
lines in both the horizontal and vertical direction.
 
6.	If the red and blue lines are not equally spaced, perform the 
symmetry adjustments described in 3.7, "CRT Neck Components 
(Adjustments)". 
 
7.	Converge red, green and blue lines at the screen center using the 
center horizontal convergence potentiometer (RV23) and the center 
vertical convergence potentiometer (RV8). 
 
3.4.3 Yoke Squareness Check 

1. Display the crosshatch pattern. 
 
2.	Check that the top and bottom of the pattern are parallel with the 
edges of the bezel. 
 
3.	If this requirement is not met, perform the Yoke Squareness 
Adjustment described in 3.7.3.1, "Yoke Squareness Adjustment". 
 
Chapter 3. Alignment Procedures  3-7 
 
3.5 
 
3.5.1 
 
Dynamic Convergence Adjustment 
 
The object of convergence is to cause the three electron beams to 
overlay each other with their respective colors (red, green, and blue) 
to form a white line. 
 
The vertical and horizontal convergence control knobs in the front 
access panel must be set to their center detent positions 
 
Before proceeding with these steps, follow the steps under3.1, 
"Prerequisites" and3.2, "Preliminary Adjustments".

Procedure 
 
1.	With power off, remove the cover and the EMC shield from the 5081, 
Unlatch the "L1" PCB from the "L" PCB and mount it in the slots directly 
behind the top right comer of the bezel. See Figure 3. Two 
groups of fffteen potentiometers are located on the component side of 
the "L1" PCB. The vertical group moves the electron beam in a vertical 
direction and the horizontal group moves the beam in a horizontal 
direction. The layout of the potentiometers relates to the parts of the 
screen they control when viewed from the component side of the board. 
Refer to figure 7. For example, the upper left potentiometer corrects
convergence in the upper left comer, the center potentiometer corrects
convergence in the center, etc. 
 
2. Power on the 5081. 
 
3. Display the crosshatch test pattern. 
 
4.	Tum the center horizontal convergence potentiometer (RV23) to its 
center position, that is, midway between full ccw and full cw. 
 
5. Master Static Convergence 
 
Place the "D" PCB in the service position. Adjust the master horizontal 
static convergence potentiometer located on the high-voltage assembly to 
converge the vertical lines of red, green, and blue at the center of 
the screen. (This potentiometer will move the vertical lines in the 
crosshatch pattem in a horizontal direction only.) 
 
6. Horizontal convergence (RV16) thru (RV30) 
 
Note: The convergence adjustments must be made in the sequence given in 
Figure 7.
 
Start with the center potentiometer of the horizontal group (RV23) and 
adjust the vertical line at the center of the screen to produce a pure 
white line. Adjust the top center potentiometer (RV21) to produce a 
converged vertical line at the top center of the screen. Adjust the top 
center intermediate potentiometer (RV22) to converge the vertical center 
line midway between the center and top of the screen. This same 
procedure will be followed for the remaining horizontal potentiometers 
in their respective areas. 
 
When all fffteen horizontal potentiometers have been adjusted, go to the 
next procedure. 
 
3-8	5081 Model 19 MIM 
 
Note: It is not necessary to repeat this sequence or to "touch up" if 
care is used and the sequence is followed. 
 
7. Vertical Convergence (RVI) thru (RV15) 
 
Note: The convergence adjustments must be made in the sequence given in 
Figure 7.
 
Start with the center potentiometer of the vertical group (RVg) and 
adjust all 15 potentiometers in sequential order to make white 
horizontal lines with no color fringing above or below the lines. This 
procedure is similar to horizontal convergence but moves the, horizontal 
lines in a vertical direction to converge red and blue into green to 
form white. 
 
8. Return the "LI" PCB to its home position on the "L~' PCB. 
 
9. Return all PCBs to the operating position. Replace all covers. 
 
Chapter 3. Alignment Procedures  3-9 
 
 
 
3.6.1 
 
Video Amplifier Alignment Before proceeding with these steps, follow the 
steps under 3.1, "Prerequisites" and 3.2, "Preliminary  Adjustments". 
 
This procedure establishes the video amplifier operating voltage levels 
and cathode currents for color balance. It is important that this 
procedure be followed carefully to produce a bright screen image with 
the proper color balance and hue. 
 
Procedure Overview 
1.	The red drive is set to a specified voltage and the red background 
is set to a specified voltage. 
 
2.	Green and blue drive potentiometers are set to provide a balance 
of cathode currents to produce a pure white on an all-white field. 
 
3.	Green and blue background potentiometers are then set to provide 
the proper color balance of red, green, and blue to produce a pure gray 
at the right haft of the gray scale on the color bar test pattern. The 
gray scale is observed at the end of the procedure to ensure proper 
color balance. 
 
4.	Drive adjustments affect the settings of background adjustments 
and Background affects the setting of drive. In order to rcfinimize the 
number of times through the loop going from Drive adjustments to 
Background adjustments, the Background adjustment is made with a 50% 
overshoot. That is, it is adjusted 50% farther than specified. See 
explanation at 3.6.4.1, "Alignment Summary". 
 
5.	The drive current adjustment and background current adjustment 
affect each other. Paragraph 3.6.4, "Green and Blue Background and Drive 
Current Adjustment" contains a procedure to measure the 
number of times drive and background adjustments will have to be 
repeated. 
 
6.	When green and blue backgrounds are tested and found to be within 
tolerance, no further drive or background adjustments need be made. 
 
7.	The setting of the screen potentiometer is checked to ensure the 
image background is black. 
 
8.	As a final check, the color bar test pattern is observed to ensure 
that gray scale steps 2 through 7 are steps of neutral gray with no 
discernible color. Very small adjustments may be made to green or blue 
(not red) to improve the gray scale. Do not adjust red drive. The left 
side of the color bar gray scale is affected by green and blue drive 
adjustments. The right side of the color bar gray scale is affected by 
green and blue background adjustments. 
 
3-10 508X Model 19 MIM