使用ALC关闭仪器工作正常， 当ALC开启时事情就会变得混乱

这是不寻常的行为。
如果ALC失败，它通常会将源发送到最大级别，因此它仍将处于相位状态。
创建A和R接收器跟踪，并查看ALC关闭和ALC的功率级别。
如果功率非常低，则可能是ALC板上的问题。
通常，如果探测器微电路发生故障，它会以一种使电路认为功率太低的方式发生故障，因此ALC环路通过将电源推向最大功率而失效。
但在这种情况下，由于锁相丢失，它似乎以最小化信号的方式失败。
环路中有许多有源IC（运算放大器，开关，DAC）;
任何一个故障都可能导致环路进入低功耗状态。



     以下为原文

  This is unusual behavior.  If the ALC fails it usually sends the source up to the max level, so it will still phase look.  Create an A and an R receiver trace and see what the power level is for the ALC off and ALC on cases.

If the power is very low, it might be a problem on the ALC board.  Usually if the detector microcircuit fails, it fails in a way that makes the circuit think the power is too low and so the ALC loop fails by pushing the source to max power.  But in this case since phase lock is lost, it seems to fail in a way that minimizes the signal.   Lots of active IC's in the loop (op-amps, switches, DACs); a fail in any of them could rail the loop to the low power state.