36
4. No Voltage Output, Faulty Output.
a. Using a scope observe TP2 on the Voltage Oscillator (08-119-001), it should be a clean sine
wave approximately 4 volts peak to peak. If not proceed to b. If the sine wave is present at
TP2, proceed to f.
b. Check for +1.000VDC at TP7 of the CVA Module, if not present or incorrect check operation
of the Voltage D to A converter, IC4 and AR5 on the CVA Module. Check for a digital high
level on pin 21 of IC4.
c. Normal operation causes a 1 volt negative half sine wave at TP15 of Phase Control and
Sense Module. If there is no output signal TP15 should read 0±1mVDC. If not check
operation of AR10 and IC8 on the Phase Control and Sense Module.
d. If no signal is present at the output, check TP12 on the Phase Control and Sense for
approximately -11VDC. If correct; check operation of AR12 and IC8; pins 6, 7,8. If IC8 is
suspected, it may be removed from its socket to isolate it.
e. If steps B, C and D are detect no fault, remove Oscillator U17-Q3 from its socket. Enter
50Hz and 10.0V and observe for a clean sine wave at TP2 on the Voltage Oscillator. If none,
replace U17-Q3, enter 10.0V and adjust R153 on the Voltage Oscillator from its present
position to clockwise and/or counter clockwise extremes. If oscillations occur readjust for
minimum AC signal at TP6 of the Voltage Oscillator. If still no oscillations, check the DC level
at TP1, TP2 and TP3 for approximately 0 VDC. If not, isolate the fault to AR9, AR10, AR11
or IC4, IC5.
f. If an AC voltage appears at TP2, but not at the output terminals, the signal must be traced
through the CVA Module, the rear panel Q11, Q12, T3, the Output Relay Assembly and the
connections to the Output terminals. Make sure logic signals are correct; CVA Module IC9
pin 9 is asserted with a TTL low level. Relays K7 and K9 of the Output Relay Assembly are
de-energized; K8 is energized. Review the possible malfunctions in 2 above and examine for
discontinuous connections or failed relays.
4.5.4 Suspected Current Failure
1. Faulty External Connections - High Resistance or Inductance.
The most common fault in the current function is poor connections, high lead resistance or
inductance, particularly for currents greater than 10.999 Amperes. This fault is made evident by
the overload failure indicator. Under this circumstance the Calibrator has a maximum compliance
of 400 millivolts RMS. Make sure the external current connections are #6 gage or greater,
shorter than 2 feet (.61 meters) in length and free of corrosion. Welding wire provides flexibility
even at this heavy gage.
2. Faulty Internal Connections.
If an overload occurs for high currents on the 10 Amp and 50 Amp ranges regardless of load,
connect a short between the Hi I and Lo I terminals. Examine the internal connections to the
current output terminals for tightness and relays K1 and K5A of the Output Relay Assembly.
To Next Page
Loading...