Stairmaster 8G Gauntlet User manual

SERVICE
MANUAL
8 Series Gauntlet
Core Health & Fitness

Page 2
StairMaster 8G Gauntlet
• Product Details & General Features
• Part Identication & Component Theory
• Installation
• Wiring / Wiring Diagram
• Power Flow
• Signal Flow
• Preventative Maintenance
• Troubleshooting & Part Replacement

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Product Details
MEET THE MACHINE THE ENTIRE GYM LOOKS UP TO.
Beginning with the rst stepping machine in 1983, StairMaster® has been a legendary name in the gym. Today the tra-
dition continues with the Gauntlet®. Building on 30 years of experience and proven performance, the Gauntlet provides
a superior combination of cardio and strength training in our most comfortable design ever. The machine features a
deeper, wider step surface with durable, rust-free polypropylene construction and is now available with all three smart,
aordable, exible, OpenHub™ console options. Its combination of quality and innovation delivers a workout that’s head
and shoulders above anything else in the gym.
Length 58 in (147 cm)
Width 34 in (86 cm)
Height 89 in (226 cm)
User Weight Capacity 350 lbs (159 kg)
SKU 9-5250-8G
Available with all three OpenHub™ console options:
• The Landmark Challenge program allows users to climb well-known landmarks from around the world like the
Eiel Tower, the Statue of Liberty and the Taj Mahal. Standard console programs are also included
• Electronically controlled alternator, brake and drive chain precisely control the stair speed, allowing a wide
range of users to exercise smoothly within their comfort zones
• Hot bar with stop button, heart rate, and level control
• Revolving staircase with eight steps, 8 in (20 cm) high, 9 in (23 cm) deep and 22 in (56 cm) wide
• 24 to 162 steps per minute
• User weight capacity 350 lbs (159 kg)

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Preventative Maintenance
With durable, high performance components, the 8 Series Gauntlet is designed for heavy usage with minimal main-
tenance required. To keep it in top condition, perform regular daily, weekly, and monthly preventative maintenance
routines outlined below. It is the sole responsibility of the owner of this equipment to ensure that regular maintenance
is performed. Worn or damaged parts must be replaced immediately, or the equipment removed from service until the
repair is made.
Cleaning
Do not use glass cleaners or any other household cleaners on the console. As per the Preventative Maintenance
schedule in the Owner’s Manual, the console should be cleaned with a damp cloth and dried on a daily basis. Cleaning
solutions can be made of a 5:1 dilution ratio, where 5 parts water are mixed with 1 part of Simple Green®, Fantastik®, or
409®. Do not spray water, or cleaner directly onto console surfaces.
Note: The safety and performance of this product can be maintained only if it is inspected regularly for damage and
wear. Pay particular attention to the components most susceptible to wear such as steps and lower side covers. Re-
move any damaged machine from service and replace damaged components immediately.
Maintenance Schedule
General Maintenance Daily Weekly Monthly Comments
Check Safety & Warning Labels X
Spot Check Step Chains X
Alternator Belt Tension XTension to 40-54 lbs-inch
Lubrication
Drive Chains X
(or every 300 hours) 30W Motor Oil
Bearing Plate XMulti-Purpose Grease/White Lithium
Cleaning
Clean Console XClean with a water dampened
cloth & wipe dry after cleaning
Clean Side Covers XClean exterior with soap & water,
or diluted household cleaner
If there are particles of dirt lodged between the buttons and console use the tip of a zip tie or business card to encircle
the perimeter of the button to loosen the debris. Once complete, use canned air to remove it from the console.
External Power Supply
The external power supply is supplied with the unit and plugs into a standard 115 volt, 15 amp outlet, or a 220-240 volt
50Hz, 10 amp outlet. All major voltage plugs are available. The power supply converts the voltage and sends it to the 8G
via a wire to the power inlet. The power inlet is located on the inside lower right leg of the machine.

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Part Identication & Component Theory
Drive System
The 8G drive system is a 3 part system that combines an alternator that provides resistance, a gear box that handles the
torque load and to ensure gearing up/down is handled appropriately during a user workout and while braking, and
the brake that prevents the steps from moving while stopped. This in turn is connected to the steps through the upper
sprocket and the chains that are directly connected to the steps. In the diagram above you can see the entire drive
system and the unit frame isolated from other parts and cabling. The upper sprocket has an inner sprocket that con-
nects the drive chain to the gear box sprocket. There is an idler arm and sprocket on the gear box to assist with keeping
tension on the drive chain. The idler arm moves with the chain and ensures that the bolt that connects it to the gear box
is not over tensioned.

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Pillow Block Bearing
Frame
Pillow Block Screw
Bearing Plate
Lower Sprocket
Pillow Block Bearing
Frame
Pillow Block Screw
Bearing Plate
Lower Sprocket
Pillow Block Adjustment Screw
Upper Sprocket
The upper and lower sprockets are held to the
chassis of the machine by pillow block bearings and
connect the left-side and right-side step chains.
Pillow blocks can be adjusted on the frame to en-
sure alignment from upper to lower sprockets and
for tensioning the step chains.
As the steps rotate, bearings in the step shaft
hardware ride down the rails on bearing plates.
These bearing plates need to be greased with white
lithium, or marine grease.

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Resistance System
Alternator
Idler
Sprocket
Brake
Frame
Gear Box
Pulley
Gear Box
"Transmission"
"Speed Reducer"
Gear Box
Sprocket
Drive
Belt
Speed
Sensor
Alternator
Idler
Sprocket
Brake
Frame
Gear Box
Pulley
Gear Box
Sprocket
Drive
Belt
Speed
Sensor
Resistance is applied to the steps of the machine by use of an alternator. 12VDC power from the lower board is fed into
the alternator to control the amount of resistance it applies. The resistance system (alternator) connects the gearing
system, or gear box of the machine via a poly-V belt.
The alternator’s connection pivots allowing the poly-V belt to be tensioned. Per design it should be tensioned to 40-54
lbs*inch, or 1/4 of a turn (90 degrees) of deection. Ensure the belt is not too tight, or damage to the alternator bear-
ings or gear box housing can occur. For additional information relating to how to properly tension the belt, refer to the
Troubleshooting section.
The “engine assembly” consists of the alternator, brake and gear box. All three components are connected to the 8G
frame as shown above. Adjustments can be made between the alternator and the gear box to assist with step rate
issues. The system regulates itself via a Hall Eect Speed sensor that reads the gaps on the alternator pulley. The inner
pulley of the gear box has a set screw so the poly-V belt can be aligned with the alternator pulley.
The brake is designed to prevent the steps from moving when the unit is o or inactive. The brake can be manually
released for troubleshooting purposes when the machine shrouds are o.
The alternator in the 8G is the same as in earlier Stairmaster models, including wiring. Wiring details are on the next
page and also in the troubleshooting section of this manual.

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Step Hardware
Step Chain
Step Hinge Sha�
Step
Step Sha�
Step Riser
Hinge Clip
The steps on the 8G are a composite plastic step with a rubber tread built into step top. The step top and kick plate are
held together and to the step chains by step hinges, threaded step shafts, nylon spacers, bearings, washers, and bolts.
Step Shaft
Step Chain
Plastic
Washer
Step
Step Riser
Metal
Washer
Bearing
Step Shaft
Nut
Step Shaft
Step Chain
Plastic
Washer
Step
Step Riser
Metal
Washer
Bearing
Step Shaft
Nut

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Major Components of the Drive System
The detail view of the 8G with the drive train isolated (above) shows the upper sprocket connection to the gear box via
drive chain. The gear box is in place to ensure gearing up/down is handled appropriately during a user workout. The
upper sprocket has an inner sprocket that connects the drive chain to the gear box sprocket. There is an idler arm and
sprocket on the gear box to assist with keeping tension on the drive chain.
The idler arm moves with the chain and tensions the chain that connects the sprockets. Resistance is applied to the
steps of the machine by use of an alternator. Variable power from the lower board is fed into the alternator to control the
amount of resistance it applies. A Poly-V belt connects the alternator to the brake and gearbox assembly. The alternator
is locked into position to properly tension the Poly-V belt.
The locking brake prevents the steps from moving when the unit is at rest and completely releases during use.

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Major Components of the Power System
Load Resistors
Battery 6VDC
LCB 711-3461
Main Data Cable to Display
Alternator Cable Harness
Cable to RPM Sensor
Power enters the system through a power converter brick plugged into the wall. It runs through an
EMI lter into the LCB where it is distributed to the rest of the system based on console signals. The
LCB is also connected to a pair of load resistors. The 6VDC battery on the 8G provides momentary
power to the unit during startup and is recharged by the alternator.
Wiring connections to Alternator
For a detailed view and list of alternator connections and troubleshooting, see the Troubleshooting section of this man-
ual.

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Installation
1. Remove all parts from the box
Remove all the packaging material and parts not attached to unit including shrouds, mast, hardware
card, etc. so the 8G Stepmill is ready for assembly on the shipping crate platform. Move the main as-
sembly carefully o󰀨 the shipping pallet.
Caution: The unit is very heavy. Two people may be needed to
move the frame assembly.
The following parts are included on the hardware cards. If cards or parts are missing, please call
1-800-503-1221 prior to assembly:
PART # DESCRIPTION QTY.
110-1830 NUT, 3/8-16, NYLOK HEX 6
110-1871 NUT, 5/16-18, NYLOC 4
110-3480 NUT, 3/8-16, SHN, CS, ZP, GR 5 4
120-3330 WASHER, PLAIN, ID: .375", OD: .875", TH: .06", CS, ECB 8
140-3494 PIN, COTTER, Ø.12" WIRE, 1/2"-5/8" SHAFT, CS, ZP 2
140-3495 FEET, 3/8-16 SCREW, 1.93" BASE 4
711-3285 RIVET, FLUSH, LOCK, PUSH, Ø6.5mm 34
731-0367 WASHER,PLAIN,M10 12
740-7842 WASHER, 8.4mmID X 21mm OD X 1.6mm THK 4
110-3479 SCREW, 3/8-16, 1", BHCS, CS, ECB 4
110-3481 SCREW, 3/8-16, 3 5/8", BHCS, AS, ZP 2
110-3482 SCREW, 5/16-18, 1 3/4", BHCS, AS, ZP 4
110-3510 Screw, 5/16-18, 3/4", BHCS, AS, ECB 4
711-3339 PIN, TRANSPORTATION, SM 2

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2. Install the Neck Bracket
Secure the Frame Neck Adapter to the frame
using four (4) pieces each of the 5/16”x1 3/4”
screws, 21mm OD washers, and 5/16” nylok hex
nut.
3. Rout Cables Through Mast
Slide the Mast Grommet onto the mast rst and
then the Upper Shroud Cover
Route the wires for the display up and out
through the top of the mast. Then use two (2)
pieces each of the 3/8”x3 5/8” screws, 3/8” nylok
hex nuts, and (4) pieces of Ø3/8” ID washer to
secure the Mast to the Frame Neck Adapter.
4. Mount the Handrails
Install the upper handrail beauty ring onto the top
of the lower neck as shown. Connect the heart-
rate grip wires on the left side handrails prior to
bolting.
Slide beauty ring onto both handrails of the Hot-
bar Handrail Assembly. Exert force on handrail
su󰀩cient to insure a tight seal with the beauty
ring then use two (2) pieces each of 5/16”x3/4”
screws and Ø1.6 ID washers to secure the hand-
rails to the mast per side.

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5. Secure Side Rails to Frame
Slide the Left Handrail Grommet onto the Lower
Left Handrail then repeat this step for the Right
Handrail Grommet and Lower Right Handrail. At-
tach handrails with (2) pieces each of the 3/8”x1”
screws and 3/8” nylok hex nuts and (4) pieces of
the Ø3/8” ID washers each side.
Check to ensure both the beauty rings for the
Hotbar Handrail Assembly and the rubber
grommets for both the Mast and Lower
Handrails are in place and all hardware is tight.
6. Secure Side Rails to Hotbar
Attach the Lower Left Handrails to the Hotbar
Handrail Assembly using two (2) pieces each of
5/16”x3/4” screws and .875” OD washers. Repeat
this step for the Lower Right Handrail.
7. Install Neck Shrouds
Slide the upper shroud cover and neck grommet
down the mast onto the frame ensuring the grom-
met has a good seal between the mast and the
upper shroud before securing using the plastic
rivets on the inside of the frame.

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8. Reinstall Shroud Cap
Attach the Lower Right Handrail Cover using
the plastic rivets then repeat for the Lower Left
Handrail. Slide the Lower Handrail Grommets
down and ensure a tight seal against the Lower
Shrouds and Lower Handrail Covers.
9. Install Leveling Feet
With help from another individual, tip the 8G on
its left side and install the left side Leveling Feet.
Repeat this process for the right side Leveling
Feet.
Crushing Warning: The unit is very heavy.
Two people are needed to tip this unit safely.
10. Install Display Rear Housing
Fasten the back half of the console assembly
to the Mast using the screws supplied with the
console.

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11. Connect cables to Console Board
Connect the appropriate wires coming out of the
mast to the correct locations, please reference
the console wiring guide (CSB 620-8424).
12. Secure Display
Secure the front half of the console assembly to
the back half using the screws supplied with the
console taking care not to pinch any wires and
ensuring that the rubber console grommet has a
good seal.
13. Install Transport Wheels (Optional)
The Transport Wheels can optionally be installed
to help with movement of the unit. Slide a Trans-
portation Pin through the left side of the frame.
Then, slide one Transport Wheel onto the left
side transportation pin so that the wheel sits
inside the frame. Finally, use a cotter pin to lock
the transport wheel onto the transportation pin.
Repeat these steps for the right Transportation
Wheel. Once the machine has been moved into
the desired location, remove the transport wheels
prior to use.

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14. Clamp the Power Cord
Remove the Phillips screw and place the power
cord into the clip. Then reinstall the screw.
15. Installation is Complete
Plug power into wall and perform nal checks.
Note: Be sure to set the display to correct model
in the Maintenance Mode.

Page 17
Wiring Diagrams
To Display
To Display
Speed Sensor
(140-3501)
Main Data Cable
(711-3494)
Alternator Cable Harness
(711-3351)
Battery
(580-0275)
EMI Filter
(440-0282)
Main Power Harness
W/Power Inlet
(711-3495)
Alternator/Brake/Transmission Assy
(711-3510-KT)
Resistor Assy
(711-3242)
12VDC
24VDC IN USE
9VDC
12VDC
7VDC 3VDC
12VDC
ALL VOLTAGES GIVEN WHILE MACHINE NOT IN USE
UNLESS OTHERWISE NOTED
3VDC
The 8G uses a power brick to step down the wall voltage from 110/220 to 12V nominal. The 8G does not require
a dedicated or 20A circuit, although a grounded outlet is required.

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Power Flow
A power trace tests the voltage at every junction point of electricity on the machine from the wall to the console to
validate good power ow and eliminate power as part of routine troubleshooting. Refer to the diagram above for the
general ow of a power trace of the 8G. For detailed instructions on how to perform a power trace, see below.
Warning: the following procedure requires the power to be on.
Please exercise caution when working around live electrical components
1. Using a multi-meter, test the wall outlet for
110VAC OR 220VAC*
*Voltage and current can vary depending on country.

Page 19
2. Test the power cord that connects the pow-
er adapter to the wall socket for 110VAC OR
220VAC*
*Voltage and current can vary depending on country.
3. Test for 12VDC coming from the power supply via
the barrel connection. One probe should be in-
side the barrel connector while the 2nd probe is
touching the outside of the connector as shown.
4. Test for 12VDC coming from the power inlet
cable into the EMI lter

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5. Test for 12VDC coming out of the EMI lter
6. Test for 9VDC coming out of the lower control
board (LCB) going to the main data cable
7. Test for 9VDC coming out of the main data cable
going to the console