732B/734A
Instruction Manual
5-14
6. Remove the four screws (two on each side) that fasten the rear panel to the power
transformer assembly.
7. Remove the power transformer assembly.
Troubleshooting 5-16.
When a problem occurs with the 732B, first verify that the battery is good and that the
line power fuse is intact. Then you need to determine if the problem is in the 10V
reference circuitry or the A5 Battery Charger/Power Supply assembly.
Presented first is a simple performance test for troubleshooting the 10V reference
circuitry. If the 10V reference circuit is faulty, the complete oven assembly must be
replaced as a unit. The reason for this is that repairing the reference circuitry can disrupt
the stability of the standard.
Following the 10V reference performance test is a detailed troubleshooting procedure for
the A5 Battery Charger/Power Supply. If you believe that the reference circuitry is
faulty, review the A5 troubleshooting information first. Make sure that the problem is
not in the A5 assembly before you replace an oven assembly.
10V Reference Performance Test 5-17.
To check for a failure in the 10V reference circuitry, look for any of the following
symptoms (assuming that you have allowed a warmup period of at least 24 hours):
1. The 10V output is further than ±3 mV from 10V.
2. The 1.018V output is further than ±1.5 mV from 10V.
3. When the 10V output is shorted, the short circuit current is greater than 50 mA.
4. The 10V output is excessively noisy with consistent dvm rattle of greater than 5 µV
(using a 6-1/2 or 7-1/2 digit dvm with sampling no faster than 1 per second and with
filtering on).
5. The 1.018V output is excessively noisy with consistent dvm rattle of greater than 2
µV (using a 6-1/2 or 7-1/2 digit dvm with sampling no faster than 1 per second and
with filtering on).
Troubleshooting the A5 Battery Charger Assembly 5-18.
There are six functional circuit groups in the A5 assembly:
1. Transformer/Rectifier/Filter
2. Battery Charger
3. +11.5V Preregulator
4. +11.5V Regulator
5. -6V Supply
6. IN CAL LED Logic
These groups are linked together but are autonomous enough to be checked
independently on an input/output basis. The following information describes the circuits
where necessary for understanding the troubleshooting method, but not in detail. For a
more detailed circuit description, refer to Section 4. To locate test points and
components, refer to the schematic and parts placement diagrams in Section 7.
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