Offset-vernier
Control-voltage
Output Amplifier
Caution
I
Check the offset-vernier control-voltage, received from the control
board A2 at board connector side of R501 , against Table 10.4-6:
Table 10.4-6. Offset-vernier Control-voltages
HP 8112A Setting Control voltage
HIL
LOL
at R501 (typ)
+8.0 v +7.9 v
-7.45 v
+5.5 v +4.5 v
-4.8 v
+0.5 v -0.5 v
<
lO mV
-4.5 v -5.5 v
+4.8 v
-7.9 v -8.0 v
+7.45 v
•
Do not operate the HP 8112A without the heatsinks fitted on
board Al
•
If
you need to replace one or more of the transistors Q505 - Q513,
do not attempt to remove the heatsink and transistor adaptors
together, this is likely to damage the transistors.
1 . Remove
all
the screws securing the heatsink(s).
2. Remove the heatsink(s).
3. Remove the adaptor( s) from the transistor( s) to be replaced.
4. Replace the transistor( s )
.
5. Re-fit the adaptor(s) and heatsink(s).
1. Set up the HP 8112A as follows:
RCL
101
Output
2. Press the
key
0
- 1
v
Disabled
3. Measure the voltage at CR501 and CR502 (typ. 10 mV):
If
it is fully negative (approximately -15 V) check U502, Q502,
Q504 and Q506.
If
it is fully positive (approxi 15 V) check Q50 1 , Q503,
Q505 and U502.
4. Check if Q510/Q5 1 1 or Q512/Q513 have failed (emitter-collector
short-circuit) .
If
you need to change any of the output-stage transistors Q508 -
Q513, also check CR505 and CR506. They protect the output
stage at high amplitudes and frequencies by discharging the
base-emitter capacitor of Q510 -Q513.
5. Set the HP 8112A to FIXED mode, output ENABLED.
1 0.4-14 Servicing the Shaper and Output Amplifier
Summary of Contents for 8112A
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Page 144: ...8 32 Testing Performance ...
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Page 194: ...10 2 4 Servicing the Power Supply ...
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Page 240: ...10 4 16 Servicing the Shaper and Output Amplifier ...
Page 242: ...A R l BD RY MR I N 1 2 7 I I IJt 51 CR1 B e i 1 _ _ _ _ 20 ...
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Page 262: ...A B A2 ED RY CONTROL ...
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Page 290: ...R B c R3 BD RY M I CROPROCESSOR 1 2 3 FIGURE 1 0 7 8 ...
Page 294: ... 8 X2l 2 X2 Figure A 1 Mechanical Parts 1 A 2 Replaceable Parts ...
Page 295: ...MP MP3 MP MP2 MP4 MPS MP 1 2 MPS MP MP I B ElElElEl Replaceable Parts A 3 ...
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Page 378: ...Figure B 14 Mechanical Parts 1 B 44 Backdating ...
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