Bio-Rad Helios® Gene Gun System - Manual (Page 45)

To replace the O-ring on the end of the barrel liner:
1. Remove the barrel liner.
2. Remove the old O-ring from the barrel liner.
3. Place a new O-ring in the groove and press it in gently. Do not use grease or adhesive.
To replace the O-ring around the exit port of the main valve:
1. Using a pin or syringe needle, poke the O-ring from the edge to pop it out. Be careful
not to scratch the surface of the valve.
2. Place a new O-ring in the groove and press it in gently. Do not use grease or adhesive.
10.3 Replacing the O-ring on the Tubing Prep Station
The Tubing Prep Station has two user-serviceable parts: O-rings at the end of the tubing
support cylinder nearest the motor. If the O-rings are worn, nitrogen may leak around them and
the amount of nitrogen indicated on the flowmeter will not be passing through the tubing. Under
normal use, the lifetime of the O-rings should be longer than 1 year. The O-rings may be changed
as follows (see Figure 24):
1. Remove the tubing support cylinder by pushing it to the right to contract the spring on the sup-
port bar, then raise the left side up and away from the base of the unit.
2. The outer O-ring should be located in the slot at the end of the tubing support cylinder,
although it may remain in the support on the motor housing. It may be removed with a fin-
gernail or a blunt object, such as a toothpick. If worn, replace the O-ring with a new one.
3. The inner O-ring is at the end of the tubing support cylinder next to the stem. To replace
it, remove the stainless steel stem at the end of the tubing support cylinder by loosening
the hex nut on the lower surface of the tubing support cylinder one-eighth turn using a
5/64" Allen wrench. The stem and spur gear can be pulled out of the tubing support cylin-
der. Remove the O-ring from the slot in the stem with a fingernail or blunt object and
replace if worn. Insert the stem into the end of the tubing support cylinder; press gently
on the end to hold the O-ring in place and tighten the hex nut. Replace the tubing support
cylinder in the base of the Tubing Prep Station.
Fig. 24. Replacing the O-rings on the Tubing Prep Station. The O-rings are located in the tubing support
cylinder on the side next to the motor housing. One O-ring (A) fits into a slot on the outside edge of the stem
at the end of the tubing support cylinder. The other O-ring (B) is on the inside surface of the stem and can
be removed only after loosening the hex nut and removing the stem from the tubing support cylinder.
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