OHAUS T71P, Service Manual

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CHAPTER 3 MAINTENANCE PROCEDURES
3.2.1 Main Printed Circuit Board (PCB) Replacement
Repairs are not recommended on the Main PCB. Component parts of the Main PCB are not
stocked by Ohaus. Replacement is recommended rather than repairing.
1. Unplug the Indicator from the AC power source.
2. Remove the four screws from the Bottom Housing.
3. Carefully separate the Top Housing and Bottom Housing – on the T71P, disconnect
the Display PCB’s ribbon cable from the top of the Main PCB.
4. Pull all cable connectors from their plugs on the Main PCB, including (on the
T71XW), the Display PCB’s ribbon cable from the Main PCB.
5. If cable-leads are connected to the Scale 2 Load Cell Connector J7 (see Figure 1-1),
loosen the terminal block’s set-screws and remove the leads.
6. On the T71P, remove the hex screws connecting the RS232 Interface port to the
Bottom Housing, so the port will clear when the PCB is lifted out.
7. Remove the four screws from the PCB. (…and, on the T71XW, a fifth securing the
grounding cable to the PCB on the lower left.)
CAUTION
When handling the PCB, grasp it by the edges only!
Do not touch the foil side. Static discharge may damage some components.
8. Lift out the PCB.
9. Carefully re-position the replacement PCB over the screw holes in the Top Cover.
Re-insert and tighten the screws.
10. Reconnect the cables removed in Steps 4 and 5.
11. On the T71P, re-insert the hex screws connecting the RS232 Interface port to the
Bottom Housing.
12. Close the Housing and re-insert the four screws.
13. Perform calibration procedures. (See Section 1.8.)
14.
Perform testing procedures. (See Chapter 4.)
Ohaus Corporation www.ohaus.com 3-2 7000 Series T71 Indicators Service Manual