Finnpipette Digital (Model 4500) Single Channel: How to Service and Replace the Tip Ejector Assembly

In this post:

Finnpipette Digital Tip Ejector Pusher Mechanism: Based on imprinted volume size on mechanism. Does not include cog wheel or spring. Shop tip ejector pushers.
Tip Ejector Spring – TS 1131820
Tip Ejector Button – TS 10593000
Cog Wheel – TS 10593060

(The Finnpipette Digital Single Channel is the same pipette as the Finnpipette Model 4500 Single Channel)

Background Overview:

Tip Ejector Button: Cog wheel is hidden from view and on underside of tip ejector button
Tip Ejector Pusher Mechanism: Ejector spring is hidden from view on underside of ejector pusher mechanism
White Colored Tip Ejector Sleeve: Ejector sleep fits over the shaft and allows the tips to be ejected.

Finnpipette Digital tip ejector button, tip ejector mechanism, tip ejector sleeve

Finnpipette Model 4500: How to Service and Replace the Tip Ejector Assembly

Step 1:

Gently pull downward on the white colored tip ejector sleeve until it disengages from the tip ejector assembly. Once removed, lay aside for reassembly later.

Step 2:

(Figure 1.0) Gently press upward on the tip ejector button with your thumb until it disengages from the lower portion of tip ejector mechanism. Once removed, lay the ejector button aside for reassembly later.

NOTE: (Figure 1.1) Notice the cog wheel is now visible once the ejector button is removed. Please be careful to not lose the cog when the tip ejector pusher mechanism is removed in step 3.

Figure 1.0 and 1.1. Push upward on the tip ejector button. Notice cog wheel.

Step 3:

(Figure 2.0) Gently and carefully pull the upper portion of tip ejector pusher mechanism outward and away from the pipette body. Pull just enough so the cog wheel and upper portion of the ejector pusher mechanism no longer contacts the pipette body.

Figure 2.0 and 2.1.Gently lift and pull away from the body. Slide the entire ejector mechanism upward fully.

Step 4:

(Figure 2.1) While holding the cog wheel and upper portion of the ejector pusher assembly away from the pipette body, slide the entire ejector pusher mechanism upward to disengage it fully from the body. Once disengaged, lay aside, as shown in figure 3.0.

Figure 3.0 and 3.1. Pipette body with tip ejector removed. Pusher mechanism with cog wheel and spring.

Note: In figures 3.0 and 3.1, notice the cog wheel and tip ejector spring positions/orientation. These parts can be removed for cleaning with 70% IPA and a soft bristled toothbrush. If needed, replacement parts can be found at Pipette Supplies:

Finnpipette Digital Tip Ejector Pusher Mechanism: PN: Based on imprinted volume size on mechanism and does not include cog wheel or spring. Shop tip ejector pushers.
Tip Ejector Spring – PN: TS 1131820
Tip Ejector Button -PN: TS 10593000
Cog Wheel – PN: TS 10593060

Figure 3.2: Exploited view of the ejector button, cog wheel, tip ejector pusher mechanism, and spring removed from the pipette for easier viewing purposes.

Figure 3.2. Disassembled tip ejector system

Reassembly Process:

Step 5:

Re-install the tip ejector spring and cog wheel back onto the tip ejector pusher mechanism.

Step 6:

Align the tip ejector mechanism slits with the slots on the pipette handle, as shown in figure 4.0. Push the tip ejector pusher mechanism downward until it is fully seated back onto the pipette (Figure 4.1).

Step 7:

(Figure 4.2) Re-install the tip ejector button onto the tip ejector pusher mechanism by pushing downward.

Figure 4.1 and 4.2. Reassembling the tip ejector system

Step 8:

(Figure 5.0) Re-install the white colored tip ejector back onto the pipette by aligning it with the tip ejector pusher mechanism. Once aligned, push upward until it is secure.

Step 9:

(Figure 5.1) Check reassembly by loading and ejecting tips multiple times. Re-check your work as needed.

Figure 5.0. Reassembling the ejector sleeve.

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