TIAH64D MPU-24
20
5
Unit Care and Maintenance
Check Unit Internal Resistance (Test for Shorts)
It is essential to test for shorts to detect any problems with the unit. First, set the multimeter to the “resistance”.
Next, test to see if both terminals are isolated from the chassis ground and the line ground using the steps
below. In steps 1 and 4, the multimeter should read less then 1 ohm. In steps 2, 3, 5 and 6, a reading of
greater than 10 megohms will assure no shorts exist.
Check DC Voltage Reading at DC Receptacle Terminals
To verify that the power cells are fully charged, set the digital
mulitmeter to measure dc voltage. Place the positive probe (red)
on the positive post of the DC Output Connector, as shown in Figure
7.2.3. Next, place the negative probe on the negative post. The
multimeter display should read approximately 28.5 Vdc (± 0.5 Vdc)
when power cells are fully charged and the unit is plugged into an
appropriate ac power source. When the unit is not plugged into an
ac power source, the mulitmeter display should read approximately
25.5 Vdc.
Figure 5.2.3 – Testing DC Receptacle
1. Place the negative probe on the
ac ground probe (D) and the
positive probe on an exposed
part of the metal case.
2. Move the positive probe to
the dc positive post on the DC
Output Connector.
3. Move the positive probe to the
dc negative post on the DC
Output Connector.
4. Move the positive probe to one
of the four screws securing the
DC Output Connector to the
unit casing.
5. Move the negative probe to
the dc negative post on the DC
Output Connector.
6. Move the negative probe to
the dc positive post on the DC
Output Connector.
