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Model T101 Instruction Manual Troubleshooting & Service
227
If the unit is set for 220-240 V and is plugged into 100-120 V, the analyzer will not start.
If the unit is set for 100-120 V and is plugged into 220-240 V, the circuit breaker built
into the ON/OFF Switch on the front panel will trip to the OFF position immediately
after power is switched on. Note that the analyzer will be severely damaged if 220-240
V is supplied to it when configured for 100-120 V. Never bypass the power switch or
circuit breaker.
9.5.4. DC POWER SUPPLY
If you have determined that the analyzer’s AC main power is working, but the unit is
still not operating properly, there may be a problem with one of the instrument’s
switching power supplies, which convert AC power to 5 and ±15 V (PS1) as well as +12
V DC power (PS2). The supplies can either have DC output at all or a noisy output
(fluctuating).
To assist tracing DC Power Supply problems, the wiring used to connect the various
printed circuit assemblies and DC powered components and the associated test points on
the relay board follow a standard color-coding scheme as defined in Table 11-4.
Table 9-4. DC Power Test Point and Wiring Color Code
NAME TEST POINT# COLOR DEFINITION
DGND 1 Black Digital ground
+5V 2 Red
AGND 3 Green Analog ground
+15V 4 Blue
-15V 5 Yellow
+12V 6 Purple
+12R 7 Orange 12 V return (ground) line
A voltmeter should be used to verify that the DC voltages are correct as listed in Table
11-5. An oscilloscope, in AC mode and with band limiting turned on, can be used to
evaluate if the supplies are excessively noisy (>100 mV peak-to-peak).
Table 9-5. DC Power Supply Acceptable Levels
CHECK RELAY BOARD TEST POINTS
From Test Point
To Test Point
POWER
SUPPLY
VOLTAGE
Name # Name #
MIN V MAX V
PS1 +5 DGND 1 +5 2 +4.80 +5.25
PS1 +15 AGND 3 +15 4 +13.5 +16.0
PS1 -15 AGND 3 -15V 5 -14.0 -16.0
PS1 AGND AGND 3 DGND 1 -0.05 +0.05
PS1 Chassis DGND 1 Chassis N/A -0.05 +0.05
PS2 +12 +12V Ret 6 +12V 7 +11.8 +12.5
PS2 DGND +12V Ret 6 DGND 1 -0.05 +0.05
07266B DCN6485