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M4000 Insulation Analyzer User Guide
72A-1230 Rev. F 4-51
July 22,
2005
Low-Voltage Power Checkout
Outputs of the Low Voltage Power Supply Board are readily measured at test
points accessible on the Heater/Temperature Controller Board (Figure 4.41
on page 4-80), which is mounted directly on the Low Voltage Power Supply
Board. Check the following test points for the specified DC voltages:
TP1
Ground reference
TP2 -5 V
TP3 +15 V
TP4 +5 V (>4.9 V)
TP5 -15 V
If any of the measured voltages is out of range, replace the power supply by
following the procedure in ”Replacing the Low Voltage Power Supply Board”
on page 4-78.
Guard-to-Ground Shorting Problems
Guard-to-ground shorts can be detected by following the procedure in
”Checking M4100 Guard-to-Ground Insulation” on page 4-43. A short is most
likely to be found in one of the following areas. Check each possible cause in
turn until the source of the problem is isolated:
1. Check the clearance between the Amplifier Assembly and Transformer.
They must not be touching at any point. If the instrument has been
dropped, the Amplifier Assembly in the bottom of the instrument could
have been forced upward into contact with the guard around the
Transformer. Eliminate the contact.
2. A screw or other metallic object may have fallen under the guard
surrounding the Transformer, thereby shorting the guard to the chassis.
Remove the object. This may require removing the Transformer.