Outputerr; Balance; Coarse Dac - Tektronix 11A52 Service Manual

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(if the worst-case error was at the low-gain end of the vari-gain curve), or 1.02 to infinity
(if
the worst-case (
error was at the high gain end of the vari-gain curve). If the normalized gain at the worst-case setting is
outside the appropriate limits, the test is flagged as failed, and the bandwidth-limit gain settings and gain
settings for the worst-case low- and high-gain errors are stored for later retrieval by the Explain Cal
diagnostic.
Failures in this test will cause the amplifier to emit DAC Overflow errors when the amplifier is commanded to
go to gain settings that cause the amplifier to request vari-gain settings beyond the range of the vari-gain
control.
Test Failure
Gain test failures indicate problems anywhere in the amplifier signal path, including the attenuator, M377,
and ACVS.
OUTPUT ERR
This routine checks the calconstant that characterizes the amplifier output error. The test checks the output
error of the amplifier combined with input offset of the oscilloscope (in divisions). If the combined error
exceeds ±0.55 division, the test is flagged as failed.
Test Failure
Failures in this routine may be caused by a oscilloscope with excessive input offset, bad M377 ICs in the
amplifier, or faulty ACVS channel(s) in the amplifier.
BALANCE
This routine checks the calconstants used in balancing the amplifier at various different gain settings. The gain
setting that has the worst balance error is found, and this error is checked to ensure that the balance adjustment
has enough range to correct for the balance error. If insufficient range is available, the test is flagged as failed.
The values returned by the test are the limits of the balance adjustment (-0.999 to +0.999, representing the full-
scale range of the balance adjustment) and the actual setting necessary to correct for the worst-case imbalance.
Test Failure
Test failure indicates problems with the output amplifier (M377) ICs or the attenuation buffer.
COARSE DAC
This routine checks the offset scaling error of the coarse offset calconstants. It generates a percentage error of
the characterized coarse offset scaling versus the expected nominal coarse offset scaling. If the calculated error
exceeds ±2%, the test is flagged as failed.
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11A52 Extended Service Manual
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