ACCESS TO THE DISPLAY UNIT CIRCUITRY For access to the circuits within the Terminal, remove the two screws on each side of the cover, and the two in back near the top. Then lift the cover off.
KEYBOARD INFORMATION
Perform the following procedure to get at the keyboard circuits:
1. Remove the Terminal cover.
2. Remove the three larger screws from the top rear of the keyboard.
3. Remove the three screws from the bottom-front of the keyboard panel.
4. Pull the keyboard forward, then up and out as far as the cables will allow. Then turn the keyboard over.
5. The top surface of the circuit board can be accessed by removing the eight screws that hold the keyboard assembly to the keyboard panel.
Key caps can be removed by pulling them directly away from the keyboard. Use of a large pair of tweezers or a forceps is recommended.
Keys utilize reed switches whose solder contacts are accessible on the underside of the keyboard circuit board.
Once the wires are unsoldered, the reeds can be extracted through the holes. Reverse the procedure for replacement.
Maintenance-4023 Service Groups of keys are installed in assemblies which can be removed once the nuts are removed from the underside of the circuit board.
CIRCUIT CARD INFORMATION
ACCESS. For access, remove the Terminal cover.
CIRCUIT CARD REMOVAL. The circuit cards plug into the minibus and are held in by circuit card hold-down clamps. Remove these clamps, disconnect the cabling, then pull the card (cards) from the minibus.
CARD WIRING. Each card is assigned an assembly number starting with A 1, the RAM card. Fig. 1-5 illustrates the order the card assemblies are inserted into the minibus.
Cabling at the Keyboard Interface, Edit, and Control cards use the resistance color code to assure proper connection.
The plugs that attach to the afore-mentioned three cards are colored accordingly. For example, the Keyboard Inter-face (A4), has three yellow plugs attached. The green plug attaches to A5; the blue to AG.
POWER SUPPLY CARD REMOVAL. Remove the cables that connect to the power supply circuit card.
Unsolder the four wires that connect to the transformer.
Then, remove the four screws that attach the card to the switch assembly.
REAR ASSEMBLY REMOVAL
The rear assembly consists of the power supply and the Motherboard. For disassembly, follow this procedure. Refer to the illustrations in the mechanical parts list as necessary during this procedure.
1. Remove the Terminal cover.
2. Disconnect the cabling from the minibus circuit cards. For convenience, it is suggested that you remove all the circuit cards and set them aside.
3. Disconnect P210, P208, P207, and P205 from the Motherboard.
Maintenance-4023 Service
4. Remove power switch wiring (see Fig. 3-2):
a. Remove the transformer wiring top cover and disconnect the grey-red-white and grey-red-black wires from the jumper strip.
b. Remove the cover that houses S 1 001 and discon-nect the greY-black-brown and grey-white-brown wires from the NO 1 and NO 2 connections of Sl 001. Loosen the clamp and pull these wires through the clamp.
c. Disconnect the ground terminal using a 1/4 inch nut-driver or wrench.
Fig. 3-2. POWER switch wiring.
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5. Remove
th~
three machine screws that hold the rear assembly to the mainframe. One screw is on the left, near the silk screening for Cl006; the other two are on the right side, in line with the rear cable port.6. Lift up on the assembly, tipping it back and pull the POWER switch wiring through the hole. '
7. Lift the rear assembly away from the mainframe.
3-4
REAR ASSEMBLY INSTALLATION. The installation procedure is the reverse of the disassembly procedure.
MONITOR ASSEMBLY INFORMATION
The monitor assembly includes the crt, Deflection and High Voltage Circuit Board, and the mounting brackets.
Refer to the Mechanical Parts Lists as necessary during the following descriptions.
MONITOR ASSEMBLY REMOVAL. The monitor assembly is best removed by following this procedure.
I
WARNINGI
The crt may implode if it is scratched or struck severely. Do not handle the crt by its neck. Wear protective clothing and a face shield when handling
the crt.
When working around or directly with the crt adequate electrical safety precautions need to be strictly observed. ALWA YS discharge to ground the High Voltage anode lead before removing the crt.
High voltage can exist, even if the Terminal has not been operating for several days. Discharge by using a jumper strap similar to the one shown in Fig. 3-3.
CONNECT STRAP TO GROUND FIRST.
Fig. 3-3. Discharging the high voltage anode.
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1. Remove the Terminal cover.
2. Remove the logic cards from the Motherboard.
3. Disconnect Jl12 from the Monitor Circuit board.
4. Remove the four 3/B-inch machine nuts that bolt the monitor to the mainframe.
5. Remove the machine screw near the left rear corner of the monitor circuit card.
6. Gently lift the monitor assembly out from the Terminal mainframe, and set the assembly on a foam rubber pad, being careful not to bump or scratch the crt.
CRT REMOVAL. The easiest and safest procedure for crt removal is to first remove the monitor assembly from the mainframe, then:
1. See WARNING under Monitor Assembly Removal.
2. Disconnect the plug from the rear of the neck by pulling gently and evenly on the plug.
3. Remove the ring magnets from the base of the crt neck by loosening the clamp screw and pulling the magnet assembly off the neck.
4. Remove the deflection coils in the same manner.
5. Remove the High Voltage anode lead by inserting a grounded screwdriver under the rubber grommet (see Fig. 3-3) and pushing when the screwdriver tip makes contact with the wire conductor. This allows one of the wire hooks to be removed from the anode connection.
Twist the connector out and up to remove the other anode hook.
6. Remove the four machine screws that hold the monitor to the frame. HOLD THE MONITOR WITH ONE HAND TO PREVENT IT FROM FALLING WHEN THE LAST SCREW IS REMOVED.
MONITOR (CRT) INSTALLATION. Reverse the Monitor disassembly procedure.
DEFLECTION AMPLIFIER AND HIGH VOLTAGE BOARD. This board is best removed with the monitor
Maintenance-4023 Service assembly removed. Disconnect all the plugs and pull the board up from the plastic tabs, a corner at a time. For installation, plug identification is provided by an illus-tration beside the board.
HIGH VOLTAGE TRANSFORMER REMOVAL.
I
WARNINGI
Be sure to discharge the High Voltage anode lead;
otherwise, personal injury may result.
1. Remove the monitor assembly from the mainframe.
2. Disconnect P104, P105, and the High Voltage anode.
3. Place the monitor assembly face down on a foam rubber pad.
4. Remove the two nuts that hold the transformer to the bottom of the monitor assembly and remove the transformer.
To install the High Voltage transformer, reverse the above procedure.
NOTE
After replacement or reassembly of any of the major afore-described Monitor assemblies, perform the display adjustments procedures provided in Section 4.
SILICON GREASE
Silicon grease is applied to both sides of the mica insulators used with the following components: 01105, 01110,01112, 0111B. In addition, silicon grease is applied to both sides of the mica insulators used with 0106 and CR103 on the Deflection and High Voltage board.
POWER TRANSFORMER INFORMATION The power transformer can be wired for use with 115 V or 230 V nominal line voltage, and can be set for any of several ranges within the nominal setting.
I nstructions for connecting the transformer are con-tained in the Installation Section. Note that the line fuse must also be changed when shifting between 115 and 230 volt operation.
Section 4-4023 Service