JLG 20VP (3120849) Service Manual - Manual (Page 52)

SECTION 2 - SERVICE PROCEDURES
2-34 – JLG Lift – 3120849
3. Adjust one mast section at a time starting from the
back (section-3, section-4, etc.) of the mast and
work forward. (i.e.. if three is OK, then jump to four,
etc.)
4. Elevate the platform until the chain/cable anchor
adjust nuts are accessible at the front and bottom of
each mast section (See Figure 2-20.).
NEVER WORK UNDER AN ELEVATED PLATFORM UNTIL PLAT-
FORM HAS BEEN SAFELY RESTRAINED FROM ANY MOVEMENT
BY BLOCKING OR OVERHEAD SLING.
5. Start with the mast section which needs adjustment
and loosen the bottom (jam) nut on each chain/
cable.
6. Tighten (to raise mast section), or loosen (to lower
mast section) the adjusting nut against the anchor
plate on each chain/cable. Adjust the nut the
amount required to raise or lower the top of the mast
section so it is even with the previous mast section
when the mast is retracted.
NOTE: It is more important that the (threaded ends) studs
protruding on the adjustments are equal side to side
on a mast section, than it is that the tension in the
chains is equal. The chain equalizers will always
assure equal tension, but if the adjustment isn’t
equal as described, the chains may tend to pull to
one side or the other.
The threaded end of the chain/cable may need to be
restrained while tightening the adjust nut to keep the
chain/cable from twisting.
7. Retract the mast all the way and check if the top of
the mast sections appear as shown in Figure 2-20.
8. Repeat steps (1) through (7) for remaining mast sec-
tions.
9. Once mast section adjustment is completed, apply
loctite #242 to the threads under the (jam) nuts that
were loosened. Then re-tighten the loosened (jam)
nuts until tight against the top (adjust) nut. Chain/
cable should have slight tension but should not be
taut.
Sequencing Cable Adjustment
1. Retract mast completely, and check each sequenc-
ing cable on outside of masts for excessive slack.
Adjust only to remove slack from cable.
2. Tighten nylock-nut just enough to remove excessive
slack from sequencing cable. The springs should
not be compressed more than 25% after adjusting.
3. Run mast through several cycles to verify cable/
chain adjustments and ensure no interference exists
between chain anchor brackets and mast.
2.11 SEQUENCE CABLE REPLACEMENT KIT
A sequence cable replacement kit is available from the
JLG Parts Department to service broken or worn
sequence cables. This kit consists of a replacement
sequence cable with the threaded (top) end attached
same as the top end of the factory cable. Also included is
a clamp (drum/socket type) to secure the bottom end of
the cable. Use the following procedure to install the
replacement cable and clamp kit.
Remove Old Cable
1. Remove the locking nut from the threaded end of
the cable at the top of the mast and then remove the
spring cap, spring, and spacer washers if installed.
2. Slide the threaded top end out of the upper anchor
bracket, then at the bottom end pull the cable out
though the sheave pulley/anchor bracket until it is
completely clear of the machine.
Replacement Cable Installation
1. Be certain the mast is completely retacted and at the
bottom of travel. Check the mast "Side Profile" at the
top of the mast as shown in Figure 2-20., adjust
mast sections to proper height if necessary.
2. To determine where the clamp will be installed at the
bottom of the replacement cable, temporarily
assemble the new replacement cable to the top
cable anchor bracket on the mast using the wash-
ers, spring, spring cap and lock nut previously dis-
assembled. Thread the lock nut on until
approximately 1/8 in. (3mm) of threads are exposed.
3. At the bottom of the mast, thread the loose end of
the replacement cable through the proper sheave
pulley and through the hole in the sheave pully/
anchor bracket on the mast section ahead of the
sheave pulley.
4. Grasp the cable and pull on the cable until the
spring at the top of the cable is slightly compressed.
Use a black marker to mark the cable on the top
side of the sheave pully/anchor bracket. This will
determine where the clamp (drum/socket) sleeve
will be positioned on the cable.
DO NOT CUT THE CABLE AT THE MARKED POINT ON THE
CABLE THIS IS ONLY USED AS A REFERENCE FOR POSITIONING
THE CABLE SLEEVE WHICH WILL REST AGAINST THE ANCHOR
BRACKET ONCE INSTALLED.