307–786
TABLE OF CONTENTS
INTRODUCTION
2
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SAFETY WARNINGS
4
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AVERTISSEMENT
6
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ADVERTENCIA
8
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SETUP
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OPERATION
11
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Startup
11
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning a Clogged Tip
12
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SHUTDOWN AND CARE
13
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FLUSHING GUIDELINES
When To Flush
14
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How to Flush
15
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TROUBLESHOOTING GUIDE
Motor Won’t Operate
16
. . . . . . . . . . . . . . . . . . . . . . .
Low Output
19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
No Output
20
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Excessive Pressure Fluctuations
20
. . . . . . . . . . . .
Motor Is Hot And Runs Intermittently
21
. . . . . . . . .
Electrical Short
21
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Spin Test
22
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Bridge Test
23
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REPAIR
General Repair Information
24
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Motor Brush Replacement
25
. . . . . . . . . . . . . . . . . .
Power Supply Cord Replacement
26
. . . . . . . . . . . .
On/Off Switch Replacement
26
. . . . . . . . . . . . . . . . .
Bridge Rectifier Replacement
27
. . . . . . . . . . . . . . .
Circuit Breaker Replacement
27
. . . . . . . . . . . . . . . .
Circuit Board Replacement
28
. . . . . . . . . . . . . . . . .
Pressure Control Replacement
29
. . . . . . . . . . . . . .
Pressure Control Adjustment
30
. . . . . . . . . . . . . . . .
Bearing Housing &
Connecting Rod Replacement
32
. . . . . . . . . . . . . . .
Drive Housing Replacement
33
. . . . . . . . . . . . . . . .
Motor Replacement
34
. . . . . . . . . . . . . . . . . . . . . . . .
Displacement Pump Repair
36
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PARTS DRAWINGS & LISTS
Displacement Pump
39
. . . . . . . . . . . . . . . . . . . . . . .
Upright Sprayer
40
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Lo-Boy Sprayer
42
. . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Control
44
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Wiring Diagram
45
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ACCESSORIES
46
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TECHNICAL DATA
47
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DIMENSIONS
47
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GRACO PHONE NUMBERS
47
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THE GRACO WARRANTY AND DISCLAIMERS
48
. .
INTRODUCTION
ULTRA
750 BASIC COMPONENTS
Your new Ultra
750 Sprayer functions and operates dif-
ferently than other airless paint sprayers. This section will
help you become familiar with the sprayer before operat-
ing it.
Pressure Control
The pressure control includes an ON/OFF switch for the
sprayer, the pressure adjusting control knob, a pressure
sensing device and a current overload circuit breaker
with a manual reset button. The function of the pressure
control is to control the motor speed so that the sprayer
maintains constant fluid pressure at the pump outlet.
Motor
The DC motor has sealed bearings and replaceable mo-
tor brushes. Its function is to drive the displacement
pump at the rate needed to supply sufficient paint volume
at the selected pressure. Working together, the pressure
control and motor cause the pump to cycle whenever
there is fluid or pressure demand. When the pump is cy-
cling, the motor sounds like an automobile starter crank-
ing. When the pump is not cycling, the motor may hum
intermittently until the fluid pressure stabilizes, then the
motor will shut itself off. However, there will still be power
to the sprayer and it will stay pressurized and ready to
use until you manually shut it off and relieve pressure.
Because the motor is DC, it is less sensitive to low volt-
age or voltage fluctuations than an AC motor
, and a
heavy gauge extension cord of up to 150 ft. (45 m) can
be used.
Drive Assembly
The sealed drive assembly transfers power from the DC
motor to the displacement pump.
Displacement Pump
The positive displacement, volume–balanced pump pro-
vides equal fluid delivery on both the up and down pump
strokes. The pump has a wet–cup which, when filled with
Graco Throat Seal Liquid, helps prevent damage to the
throat packings and piston rod.
Fluid Filter
The fluid filter strains the paint to help avoid clogs in the
hose and spray tip. The filter includes a reusable element
and has a pressure drain valve for manually relieving fluid
pressure.
Hoses
The grounded, nylon spray hoses have spring guards on
both ends. The 50 ft. (15.2 m) hose has a 1/4 in. ID. The
3 ft. (0.9 m), 3/16 in. ID hose provides more flexible gun
movement. The nylon hose material acts as a pulsation
dampener to absorb pressure fluctuations.
Spray Gun & RAC IV DripLess Tip Guard
Graco high pressure spray guns have a trigger safety
which prevents accidental triggering when it is engaged.
See the Detail in Fig 3–1. The gun provided with the
sprayer also has a filter for final paint straining. The Re-
verse–A–Clean IV SwitchTip uses high pressure fluid to
remove clogs from the spray tip without removing it from
the gun. The Reverse–A–Clean IV DripLess tip guard is
a safety feature which helps reduce the risk of fluid injec-
tion injury.