Application Note

2 Fluke Corporation Everyday troubleshooting with the Fluke 116 DMM
116, I was able to see and show
the owner that the RPM fluctua-
tions of the generator’s motor
were causing to voltage to fluc-
tuate. Although this was barely
audible, it was easily seen on
the 116 display.
Since they were new battery
back-ups, their batteries were
in a relatively discharged state.
Supplying less than their rated
minimum input (120 V) exac-
erbated the fluctuations of the
generator, dropping the power
(from the battery back-up
receptacles) to less than enough
to run the their internal charg-
ing systems and the attached
POS System.
The Min-Max recording
feature made it very easy to
show/explain the test results to
the store owner and the proj-
ect manager. All of the tests
were executed without risking
discharging the backup batter-
ies or crashing the new equip-
ment during the configuration
process.
Stereo receiver will not
turn on
Tested voltage from wall outlet
and then through power cord.
No shorts. Tested power on
circuit board before mounting
(good). Tested power on circuit
board after fuse (none). Visual
inspection of fuse was not
possible as it was enclosed in
a plastic shroud. Using the 116
validated opening the casing.
7-11 Store: No power at
Juniper Wireless Access
Point, ordering equipment/
ATM/Credit all offline as
result
Tested wall outlet voltage
(good). Tested voltage in power
cord, before it enters in-line
transformer (good). Tested
voltage at output tip (none).
Once the power supplies were
changed, if the voltage output
on the primary or redundant
was more than .001 volts lower
than the other, the unit would
begin to “sing,” (a high-pitched
squeal). That meant I had to
adjust three pots on the back of
each power supply to balance
the outputs. That’s where I
needed the high resolution of
the Fluke 116.
New UPS Store, in a newly
constructed shopping center
I was scheduled to install and
configure two POS Systems (PC,
Receipt Printer, Label Printer,
Scale, Pin-Pad, Touch Screen
Monitor, all with separate
power feeds), the manager’s
office computer/monitor/printer,
and the WAN modem/ LAN
router and switch. The local
electrical company had just
finished the power to the build-
ing shortly after I arrived. Since
this was new construction and
had never been powered on,
the contractor did not want the
owner to turn on the circuits
until his team arrived. So,
during the installation, I worked
with a gasoline-powered
generator.
Once I installed the POS
equipment, I was ready to start
the software configuration(s).
But, when I powered everything
on, the battery back-up units
began singing. That meant
there was a power issue. When
I turned on the battery back-
ups, the voltage dropped to
113.4, well below the required
120 volts we needed to insure
safe operation. But, when I
tested the voltages coming from
the generator and at all exten-
sion cords, they ranged from
126.9 to 127 volts. With the
Concluded power supply was
bad thus no need to take down
wall mounted Access Point,
ordered new power supply.
No output from automotive
sub-woofer
Tested dc volts at power feed
and remote-on connection.
Tested line-level inputs for
signal. Determined that the
internal amp was burned out
without even opening it. Open-
ing it confirmed diagnosis.
Wireless mouse intermittently
disconnects, even after
replacing batteries
Tested all batteries, all were
within 1.4-1.6 dc volts. NOT
a battery issue; was bad RF
Receiver.
PC will not boot
Wall outlet visibly damaged
so I checked ac current at the
receptacle for output/consis-
tency before proceeding. Since
current was fine, power prob-
lem was identified as internal
to PC.
Heat failure concerns
of network equipment
(Switches/Modem/Router/
Backup Hard Drives) once
relocated inside enclosed
cabinet
Temperature measured at
floor (70.3 °F), at eye level
(73.1 °F), inside bottom of
cabinet (73.4 °F), inside top
of cabinet without drives
running (77.8 °F), with drives
running, and server plugged in
(82.4 °F). Temperatures were
within operating range(s) of
connected equipment, although
previous techs had told them
temperature was too high to
utilize cabinet. Cabinet was
used successfully and concerns
were put to rest.