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Test Paragraph
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Table 5-6.
System Troubleshooting (Coni)
Fault
System won't turn on
System turns on, but no display
on the CRT for any display
mode
More than one key is inopera-
live or has the wrong effect
Only one key is inoperative
Any part of the nonvolatile
memory fails to remember
No DPL (modulation) signal on
CRT
5-40
Troubleshooting Procedure
1. Disconnect the high voltage supply from the
low voltage supply at A 1 OP1.
Check for nominal voltages of 15 VDC at pin 3
of U2 on the low voltage supply and for +12
VDC at pin 8. If either voltage is not present
replace the low voltage supply (A1).
2. Reconnect the low voltage/high voltage inter-
3.
1.
2.
1.
1.
1.
1.
2.
face and check for a nominal +9 VDC on the
collectors of 03 and 04. (The actual signal
on the collectors is a 0 VDC to +18 VDC
square wave).
If 9 volts is not present replace the high
voltage supply (A10).
If items 1 and 2 check okay replace the low
voltage supply (A1).
Check for presence of high voltage by dis-
connecting the CRT anode lead and arcing
it to the chassis. If no arc, replace the high
voltage supply.
If the high voltage supply is okay, replace the
CRT.
Replace the Processor Module (A9).
Replace the defective key switch.
Replace the Processor module (A9).
Check TP1 of the Audio Synthesizer for the
presence of the DPL signal. If not present
replace the Audio Synthesizer module.
Check for the DPL signal on pin 64 of the
Audio Synthesizer. If not present replace the
IEEE Interface module (AB). or check for the
presence of the jumpers on JB for the standard
unit.
Table 5-6.
System Troubleshooting (Cont)
Test Paragraph
Fault
Troubleshooting Procedure
3. Check for the DPL signal at TP6 of the Audio
Synthesizer. If not present replace the Audio
Synthesizer (A6).
4. Check for the DPL signal at TP4 of the Scope
Amplifier module (A2). If not present replace
the Scope/DVM control module (A3).
5. If signal switching is okay to the Scope Ampli-
tier module proceed to the scope trouble-
shooting information.
5-135
No external modulation on the
1. Check for modulation signal at TP7 of the
CRT
Audio Synthesizer module (A6). If not present
replace the Audio Synthesizer module.
2. Check for the modulation signal on pin 66 of
the Audio Synthesizer. If not present replace
the IEEE Interface module (AB), or check
for the presence of the modulation jumpers
on JB for the standard unit.
3. Continue troubleshooting at step 3 of the "no
DPL signal on the CRT".
5-136
Frequency Counter inoperative
1. Check for presence of a 1 kHz signal at TP9 of
the Audio Synthesizer (A6). If not present
check for the 10 MHz signal from the Fre-
quency Standard module (A 13) to the RF
Synthesizer (A5). If present replace the RF
Synthesizer. If not present replace the Fre-
quency Standard module.
2. If the 1 kHz signal is present check for the
presence of the signal to be counted at pins
61 and 63 of the Processor
1/0
module (A7).
If J]Ot present replace the Front Panel Inter-
face Module (A 12).
3. If signal is okay up to the Processor
1/0
module replace the Processor
1/0
module.
5-137
DVM AC mode is inoperative
1. Check for DVM signal at pin 22 of Processor
Interface module (A 12). If not present replace
the Front Panel Interface module.
2. Check for short bursts of the DVM AC signal
at TPS of the Scope/DVM Control module
(A3).
5-41
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