Chamberlain HD420EVP Owner's Manual page 9

Assembly
STEP 4 Install the chain
To avoid possible SERIOUS INJURY to finger from moving garage door opener:
ALWAYS keep hand clear of sprocket while operating opener.
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Securely attach chain spreader BEFORE operating.
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1. Pull the cable around the idler pulley and toward the trolley.
2. Connect the cable to the retaining slot on the trolley, as shown. (Figure 1)
a. Push pins of master link bar through cable link and trolley slot.
b. Push master link cap over pins and past pin notches.
c. Slide the closed end of the clip-on spring over one of the pins. Push the open end of the
clip-on spring onto the other pin.
3. With the trolley against the screwdriver, dispense the remainder of the cable/chain along the rail
toward the motor unit around the sprocket and continuing to the trolley assembly. The sprocket
teeth must engage the chain. (Figure 2)
4. Check to make sure the chain is not twisted, then connect it to the threaded shaft with the
remaining master link.
5. Thread the inner nut and lock washer onto the trolley threaded shaft.
6. Insert the trolley threaded shaft through the hole in the trolley. Be sure the chain is not twisted.
(Figure 3)
7. Loosely thread the outer nut onto the trolley threaded shaft.
8. Remove the screwdriver.
Threaded Shaft
Master
Link
HARDWARE
Figure 1
c.
b.
a.
Figure 3
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Figure 2
Sprocket
Master Link
Inner
Lock
Nut
Washer
Outer
Nut
Master
Link
Threaded
Shaft