Removal Of Digitizer Unit A8 - Fluke Autoranging CombiScope PM3370B Service Manual

CORRECTIVE MAINTENANCE PROCEDURES
NOTE: The power supply unit can be measured under working conditions, by using the extension
board with ordering code 5322 218 61479. On this board there is a jumper that can be
removed to switch off the EHT- converter. For safety reasons it is strongly recommended to
use this feature. Refer to chapter 8.8 for more faultfinding hints.
NOTE: Return the Battery Back-Up voltage to original position (X1006) on unit A6 when the
instrument is turned ON.

8.5.10 Removal of digitizer unit A8.

- Remove the screw that secures (and grounds) the unit to the bottom chassis plate.
- Slide the unit upwards out of the instrument.
- Unplug the coaxial cables from the unit (the cables and connectors have colour coded rings to
facilitate correct reinstallation).
NOTE: The IC's DARLIC (D8027) and DSP (D8069) are placed on sockets. Since these IC's have
numerous pins, special tools are recommended to pull them out of their sockets. For DSP the
type 821566-1 (for PLCC68) manufactured by AMP is a suitable tool. For DARLIC the type
TW2068 (for pin grid array) manufactured by Terminal is suitable. Reinstallation of DARLIC
requires considerable pressure; however take care that pins are not bent and that
components of the other side of the printed circuit board are not damaged.
The unit can be measured under working conditions, by using the extension board with ordering code
5322 218 61479. On this board there is a jumper that can be removed to switch off the EHT-converter
on the power supply A8. This feature needs not to be used when testing the digitizer.
8.6 INSTRUMENT REPACKING
If the instrument is to be shipped to a Service Centre for service or repair, attach a tag showing the
full address and the name of the individual at the users firm that can be contacted. The Service Centre
needs the complete instrument, its serial number and a fault description. If the original packing is not
available, repack the instrument in such a way that no damage occurs during transport.
8.7 TROUBLESHOOTING TECHNIQUES
If a fault appears, the following test sequence can be used to assist in locating the defective
component:
- Check to verify that the control settings of the instrument are correct. Consult the operating
instructions in the Operating guide.
- Check the equipment to which the instrument is connected, and check the interconnection cables.
- Verify that the instrument is properly calibrated. If it is not, start the autocalibration procedure by
pressing the CAL key for 2 seconds. If this does not solve the problem refer to Chapter 7
'Calibration Adjustment Procedure'.
- Locate the circuit(s) in which the fault is suspected: the symptom often indicates the faulty circuit.
If the power supply is defective, the symptom may appear in several circuits.
- Visually check the circuit(s) in which the fault is suspected. Often it is possible to find faults such
as 'cold' or defective solder joints, intermittent or open interconnection plugs and wires or
damaged components.
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