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3. DC Current at Output 1-10 Amp Ranges.
Set the Series 800 to 50 Hz, 100V, 150VA in Standby. Place a short from Current HI to Current
LO at the 10 Amp terminals. Adjust R66 on the CVA for ±50µV DC or less at TP8 of the CVA. If
the adjustment is not possible, replace AR4, then AR9 and finally AR8 of CVA. Then check Q1 of
CVA or Q3-10 of the Rear Panel Assembly.
4. F3, F4 Fuses Fail Repeatedly.
Examine Q3 through Q10 of the rear Panel Assembly for collector to emitter shorts. Look for
open diodes in the emitter circuit of Q1 of the CVA Module.
5. Current Amplitude Erratic - Phase Varying
Operate the Series 800 at the settings at which the malfunction is observed. Use an oscilloscope
and synchronize on the signal at TP2 of the Oscillator. Look at the signal on TP11 of the
Oscillator. If the sine wave is varying in amplitude and phase, remove AR3 of the Oscillator. If
the amplitude variation disappears, but the signal at TP11 is not synchronized, the malfunction is
in the phase loop, see 4.5.6.
6. Current Output Slightly Inaccurate
Replace AR1 or AR2 of the Output Relay Assembly.
7. No Current Output or Defective Output
a. With Low Currents.
Connect a short from Current HI to Current LO at the current output terminals and remove
fuses F3 and F4 and AR3 of the Oscillator Module. Set the Series 800 to 50Hz, 90V, 1VA,
and press Operate (resulting in 11.111mA). This is a convenient way to observe
performance without the danger of high currents flowing in the output stages and without
interference from the phase function. The voltage and current will not be synchronized.
Examine the performance of the Oscillator at TP11. It should be an undistorted sine wave
10.000 volts peak amplitude. If no signal is present, check TP4 of the Reference Module for
+10VDC. Otherwise the fault is in AR1, 2, 4, 5, 7 or 8 or switches IC2, IC3.
Trace the signal to TP3 of the CVA Module as a 0.555V RMS sine wave. Incorrect amplitude
or distortion at this point should be traced to AR3 or the components of the Current D to A
shown in detail on 08-115-001/1.
b. Full Current Signal Tracing.
Replace fuses F3, F4 and establish the conditions above, 50Hz, 90V, 1VA, Operate. If the
signal at TP4 or TP8 (CVA) is not a 0.111V RMS sine wave, remove AR8-CVA and carefully
short TP4 CVA to SG (TP13). This eliminates AR8 from the control loop. The voltage at TP8
should be 1.34 volts RMS. If not check AR9, 4, Q1, IC17, U15-CVA or Q3-Q10 Rear Panel.
U15 and IC17 can be removed without affecting performance at this setting.
Replace AR8, IC17 and U5 and remove short TP4 to SG-CVA. Establish the condition 50Hz,
110V, 100VA and connect a 2 ohm 10 watt resistor from current HI to current LO. Assert
Operate. The voltage at TP4-CVA is still a 0.111V RMS, sine wave. The voltage at TP8 is
approximately 0.33 volts.
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