HP 8559A FM:, Residual, Auto Scan Time (AST) Accuracy:

MODEL8559A SERVICE

Auto Scan Time (AST) Accuracy: Observe front panel switch positions to isolate the problem area. Auto scan time can also be affected by circuits on the Sweep Generator/Bandwidth Control Assembly A9 and the VIDEO FILTER control position. If the AST problem is band-related, the Marker Assembly A8 is the most probable cause. If the AST problem is either bandwidth- or scanwidth-related, the most probable cause is the Sweep Generator/Bandwidth Control Assembly A9. The greater the load on the AST line, the greater the current demand. The greater the current demand, the faster the sweep rate.

Residual FM: Residual FM can originate from the Second LO Driver (block E). The most common failures

are: R88, R87, R33, R34, U1, U7, R37, and R38, in that order.