MODEL
8559A
SERVICE
DPM
Accuracy
The following is a guide to troubleshooting poor DPM accuracy. Further information is included following the
circuit descriptions of the indicated assemblies.
Check
+
14.5V supply on the Frequency Control Assembly A7 (A7TP3).
Perform and verify Frequency Display Adjustment (Paragraph 5
-
30).
Verify Tuning Accuracy (Paragraph 4
-
12).
Check Marker Board Assembly
A8.
Check frequency accuracy of first and second local oscillators.
First
LO:
DPM inaccuracies become worse as the higher bands are selected (i.e., increases in harmonic
mixing mode).
Second
LO:
DPM inaccuracies are constant in all bands.
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