122 E8257D/67D, E8663D PSG Signal Generators Service GuideTroubleshootingTroubleshooting the RF PathTroubleshooting the RF PathTroubleshooting RF Path procedure:— preset the signal generator— set a frequency— open ALC loop (ALC Off)— set signal generator to maximum power— check power levels in the RF path using “Troubleshooting RF PowerLevels”, below.Troubleshooting RF Power LevelsThe following information has been provided to aid in troubleshooting powerlevels in the RF path:— RF Block Diagrams (see Figure 1-9 on page 167 and Figure 1-10 onpage 169 for the E8257D, and Figure 1-13 on page 175 and Figure 1-14 onpage 177 for the E8267D). The block diagrams show signal flow, pathfrequency ranges, and minimum power levels ts a few key points in the RFpath.— A Gain/Loss table (Table 1-28 on page 165). The table provides theminimum gain or maximum loss level between the input and output foreach partWhen troubleshooting the instrument, the troubleshooting procedure mayrefer you to the RF Block Diagram, the Gain/Loss table, or both.Examples:Verifying the gain or loss of a part – Locate the part in the Gain/Loss table.Measure the output and input power levels. Subtract the input from the outputto determine the gain or loss. If the part is not meeting the gains or lossesspecified (the gain is less than specified or the loss is more than specified), thepart most likely needs to be replaced. In cases where the part fails to meet itsspecification but comes very close, calculate and measure the minimum inputpower level into the part before replacing the part.Verifying the minimum power into a part – Locate a point on the RF pathwhere output power is specified, then use the Gain/Loss table to calculate theminimum power level at the specific location. If the minimum power level is notpresent, measure the output of the first device showing a power level on the RFBlock Diagram, then measure the input and output power level for each devicein the path until the defective part is located.ALC and RF problems1. Run a full self–test and troubleshoot any reported failures beforeproceeding.
