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8-148. Warm-Up Error Amplifier Troubleshooting
8-149. This procedure assumes the power amplifier is functioning properly.
a.
Set HEATER jumper to OFF. A3TP11 waveform (see Figure 8-20) changes to 0 Vdc. If
yes, go to step b. If no, go to power amplifier servicing.
b.
Is A3TP15 voltage +0.2 to +0.6 Vdc? If yes, go to step c. If no, A3R18, R19 or U14 is
faulty.
c.
Check A3R16 (SET TEMP potentiometer) to see if it is shorted. Short A3TP15 to TP11.
Measure U14 (Pin 6). Does the voltage stabilize between -1.5 V and +1.5 Vdc? If yes, go
to step d. If no, A3R21, R23 or U14 is faulty. Remove short.
d.
Short A3TP15 to ground (TP18). Is A3U14 (Pin 6) more negative than -12 V? If yes, go to
step e. If no, U14 is faulty. Remove short.
e.
Is voltage at A3U15 (Pin 3) approximately half of U14 (Pin 6) voltage? If yes, go to step f.
If no, A3R25, R26, U12 or U15 is faulty.
f.
Is voltage at A3U15 (Pin 2) between +1.2 Vdc and +1.3 Vdc? If yes, go to step g. lf no,
A3R28, R29, R30 or U15 is faulty.
g.
Is A3U15 (Pin 7) > +3 Vdc? If yes, go to step h. If no, A3R5E, R48D, U8A, or U15 is bad.
h.
Remove TP15 short and short TP11 to ground. Is A3U14 (Pin 6) voltage> +12 Vdc? If
yes, go to step i. If not, U14 is bad.
i.
Is A3U15 (Pin 7) between 0.05 and 0.15? If yes, the warmup error amplifier is OK. If no,
A3R5E, R48D, U8A or U15 is faulty.
8-150. Power Supply Troubleshooting
8-151. If the correct voltage is not observed on A3TP8, 9, or 10, typical power supply troubleshooting
should be followed. +15 V, -15V, and +5V test points must meet the limits listed in Table 8-5.
The following are suggested points to check:
a.
External system power source.
b.
A3L 1 and A3L2 are in series with the ±15V power supplies.
c.
There should be >200 Ohms from +15V to ground.
d.
If A1F2 blows (-15V line, 1.5A), check for open in A1R11, A1R12, or thermally caused
damage to WHT/ORN wire lead to [A1J3 (Pin 2)], or excessive current being drawn by
the High Voltage Power Supply. (See High Voltage Power Supply Troubleshooting in
paragraph 8-89.)
e.
Power supply components are located on both A1 and A3.
8-46
Table 8-5. Voltage Testpoints and Limits
A3 Test Points
TP8
TP9
TP10
Voltage Limits
+14V ± 0.3 Vdc
-15V ± 0.3 Vdc
+5V ± 0.25 Vdc
HP5501B
Service
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Table of Contents
Troubleshooting
