Attengain; Step Gain; Bwlmatch; Gain - Tektronix 11A52 Service Manual

Diagnostics
( ATTENGAIN
This routine checks the gain error of the worst-performing attenuator setting. The error is displayed as a
percentage error, with an allowable range of ±2%. If the Atten Gain test fails, it indicates that one or more of
the attenuator ranges does not exhibit the proper attenuation. If this test fails, the attenuator settings with
the most negative and most positive attenuation error are stored for later retrieval by the Explain Cal
diagnostic.
Test Failure
Possible causes of the test failm:e can be faulty attenuator maglatch relays, dirty
I
corroded maglatch relay
contacts, faulty attenuator buffer amplifier, failing maglatch relay driver stages, bad interconnections between
the main circuit board and the attenuator, or bad connection from the attenuator to the rest of the signal path
(coaxial cable).
STEP GAIN
This routine checks the gain error of the worst performing M377 (U310 or U410) step gain setting. The error is
displayed as a percentage error, which the calibration system must correct, with an allowable range of ±3%.
Failure of the Step Gain test causes the step gain setting exhibiting the most positive gain error and the most
negative gain error to be stored for later retrieval by the Explain Cal diagnostic.
Test Failure
If the Step Gain test fails, it indicates that one or more of the M377 step gain settings is not exhibiting the
correct gain.
BWLMATCH
This routine checks the bandwidth-limit gain error calconstants for each bandwidth limit setting. The
calconstant for the bandwidth limit setting which exhibits the worst bandwidth limit gain error is checked to
ensure that the error is within ±2% of nominal. The error indicates how much the calibration system must
correct the
gain~
If the calconstants indicate a bandwidth-limit gain error in excess of ±2%, the test is flagged
as failed, and the bandwidth limit settings with the most negative and most positive bandwidth-limit gain
error are stored for later retrieval by the Explain Cal diagnostic.
Test Failure
Failure of this test indicates a problem with the output amplifier (M377) ICs.
GAIN
This routine checks to ensure that the variable gain adjustment can correct for the worst-case low- and high-
gain errors while remaining within the characterized portion of the vari-gain control's adjustment range. The
test is done using only the calconstants generated during the last amplifier calibration cycle. The error-limits
reported for this test vary depending on which setting failed the test. The test ranges can either be from 0 to .39
11A52 Extended Service Manual 4-13