Disassembly and repair. Welch Allyn GS 777

The Welch Allyn GS 777 Wall Transformer is a compact and versatile power source for Welch Allyn's 3.5V instrument heads, ideal for use in clinical settings. It features two independent charging cradles for simultaneous use of two instrument heads while providing power to other supported Welch Allyn devices via a USB port, making it a convenient and efficient power solution.

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Disassembly and repair

These procedures provide instructions for system disassembly and board removal. Except where otherwise noted, the assembly procedure is the reverse of the disassembly procedure.

Each procedure may include the following:

• Reassembly notes: This contains information specific to reassembly not addressed in the disassembly instructions.

WARNING Electrical shock hazard. Disconnect power before opening the device.

Caution Before disassembling the device, disconnect the USB power cord and any attached accessories.

Caution Perform all repair procedures at a static-protected station.

Caution When the system case is opened, regard all parts as extremely fragile.

Execute all procedure steps with care and precision.

Caution Observe screw torque specifications, especially with screws that secure directly into plastic standoffs.

Caution To avoid mismatching screws and holes, keep the screws for each piece with that piece as you remove modules and circuit assemblies.

Required tools and equipment

• #2 Phillips bit

• Screw driver calibrated for 6.0 in-lb ±1.0 in-lb

• #10 Torx bit

• Torque driver calibrated for 7.5 in-lb ±0.5 in-lb

• Needle-nose pliers

Remove rear housing, handles, circuit board, cradle wire harnesses, and cradles

Remove the rear housing

Disconnect the USB power cord and any attached accessories.

a. Remove the device from the wall.

16 Disassembly and repair Welch Allyn GS 777 Wall Transformer b. Disconnect the USB cable.

c. Remove the rear housing by removing the four large Phillips screws.

d. Lift and remove the rear housing.

Remove the handles

e. Disconnect the handle connector wires from the PCBA.

Service manual Disassembly and repair 17 f.

Lift and remove the handle cables from the front handle housing.

Reassembly note When reconnecting the handle connection wires to the handle

PCBA, the connecting wires must be facing up and away from the PCBA.

Remove the circuit board

g. Disconnect the two IR wire connectors from the Circuit board.

h. Remove the three torx screws.

Lift and remove the Circuit board.

Reassembly note When reconnecting the IR wire connectors to the handle PCBA, the connecting wires must be facing down and toward the cradle assemblies.

18 Disassembly and repair Welch Allyn GS 777 Wall Transformer

Remove the handle cradle and optical assemblies

On the rear of the assembly, disconnect both IR wires from the optical sensors.

k. Push in the snap tabs and then remove the cradle assembly by pushing outward.

Reassembly note For ease of assembly, connect the IR wire assemblies to the optical sensors before attaching the handle cradle to the handle assembly housing.

• Attach the connector with the black and white wires to the optical detector

(indicated by the letter "B" molded into the cradle plastic). Attach the connector with the red and white wires to the optical emitter. The wires should face inward once the handle cradle is assembled.

Snap the handle cradle assembly into the front housing. Make sure that the cradle assembly tab and the beveled edge are at the top of the housing.

Key features

Two charging cradles
USB power output
Compact size
Provides power to supported Welch Allyn devices
Automatic handle power on/off when removed/returned to cradle

Frequently asked questions

The GS 777 Wall Transformer is compatible with all Welch Allyn 3.5V instrument heads.

The GS 777 Wall Transformer is powered via a USB connection. It can be connected to a computer or a separate USB power adapter.

Yes, the GS 777 Wall Transformer has a USB power output that can be used to charge or power other supported Welch Allyn devices.

The GS 777 Wall Transformer can be cleaned with a clean cloth dampened with 70 percent isopropyl alcohol or 10 percent chlorine bleach solution. Alternatively, you can use Sani-Cloth® Plus or CaviWipes™. Note, do not use CaviWipes to clean the blue handle cradles.