2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

Implementing Method #1CAUTIONThis test will be conducted with the Power Switch ON( I ). Pleaseremove aU jewelry from your hands and arms when performing this test.ATTENTION The dc voltmeter used to measure the voltages should have aninternal movement resistance of at least 20,000 ohms/volt to prevent damage tothe 7171 and to provide an accurate voltage level reading.Open the 7171 front cover and observe the visible end of any inserted TC card.Located on the upper and lower portion of the visible TC card end are two pairs ofplastic coated voltage probe test points. From the top of the card to the bottom ofthe card they are labeled TP1, TP2 and TP3, TP4. TP1 connects to +5 volts, TP2to ground, TP3 to + 12 volts, and TP4 connects to -12 volts.Set your voltmeter to the proper scale, select the proper polarity for the voltmeterprobe points and proceed to measure the respective voltages.If the power supply voltage measure outside of the voltage tolerance range, proceedwith Method #2.Acceptable Power Supply Voltage Level Tolerance Range~I1. +5 volts ----------- +4.75 volts to +5.25 volts2. + 12 volts ---------- + 10.8 volts to + 13.2 volts3. -12 volts ---------- -10.8 volts to -13.2 voltsImplementing Method #2CAUTIONTurn the Power Switch OFF(O) and REMOVE THE LINE CORDFROM THE POWER OUTLET RECEPTACLE.1. Remove the fan plugs and the dc power cable from the power supply. Removethe power supply cord from the Line Junction Box.2. Remove the power supply and replace with a new one. If the new powersupply has two metallic shipping plates held in place with thumb screws on theunder side, remove them before installing the supply.3. Insert the fan cables and the dc power cable into the power supply. Insert thepower supply cable into the Line Junction Box.4. Insert the Line Cord into the power outlet.)5. Turn the Power Switch to ON( I).6. Verify that the intermittent problem is resolved.7. If problem is not resolved, invoke your Support Structure.Chapter 8. Problem Determination 8-23