Fluke 2180A - Manual (Page 38)

2180A
Table 4-4. 2180A Troubleshooting
STEP
NO.
ACTION
Go to the step
number given
for correct
response
YES NO
1 Input 0 volts from the divider to +S (HI); —S, —V (LO); leave +V disconnected.
2 Set the RTD selector switch to setting 9 (Cal).
3 Apply power to the thermometer.
4 Does the display read 2180.X for ten seconds and then change to 0°C (0°F)? 14 5
NOTE
X = a numeral depending on the version of software installed.
5 Does any portion of the display illuminate? 13 6
6 Measure between TP2 (REF) and TP4 for +5 ±10% VDC, between TP1 (REF) and TP3 for +15 ±5% VDC.
7 Are all voltages correct? 12 8
8 Measure between pin 8 of T2 and the negative end of C26 for a DC voltage greater than 10.3V and for a
peak-to-peak wave form between pins 8 and 9 of T2 approximately twice the value of the DC voltage
measured at pin 8.
9 Are both signals present and correct? 11 10
10 Check the inverter circuit that drives the transformer (T2). Repair as required then resume at step 3.
11 Check the transformer secondaries and if any are bad, check the Individual regulators and their associated
components. NOTE: Analog circuitry may load down the ±15V supplies. Repair as required then resume
at step 3.
12 Check the +5V path to the Display PCB and the Display PCB Connector. Repair as required then resume at
step 3.
13 Check the strobes (U9-3, 4, 5,6,19) and display seven segment control lines (U9-8,9,10,11,12,13,14).
Repair as required then resume at step.3.
14 Set the RTD selector switch to the setting of the type RTD to be connected In the next step.
15 Connect an RTD to the thermometer and measure some known temperature. (A lag bath is suggested.)
16 Is the displayed temperature correct? 37 17
17 Check the RTD components and the ground sense buffer amp (U7, Q20 and their associated components).
Repair as required then resume at step 14.
18 Can the Calibration Adjustment Procedure be performed? 37 19
19 Are control signals at U9 pins 26, 27, 30, 31,32 toggling between high and low logic levels? NOTE: the X100
signal at pin 33 of U9 will remain low (OV) unless unit is in 0.1 Range. (Use TP2 as common.) 21 20
20 Replace the microcomputer U9, then resume at step 14.
21 Are the outputs of U13 toggling between high and low logic levels? NOTE: The output at pin 1 of U13 will
remain low (OV) unless 2180 is in 0.1 Range. 23 22
4-8