ESA-L E4408B高频段的频率具有10dB aprox的衰减

我有一个E4408B显然在高频段有平坦度故障仪器完成开机例程并执行自动对齐没有任何问题。
低频段工作正常。
高频段（从1到4）在3GHz以上的所有频率都具有10dB aprox的衰减。使用服务手册，我检查了A8，RF衰减器和RF输入连接器的状态。
他们很好。
但是，我怀疑LOIS（A8A4），RYTHM（A8A6）和A7A4（FEA）。
根据服务手册规范，LOIS输出LO（A8A4J2）的幅度为3dB。来自RYTHM（A8A6）的高频段IF输出根据服务手册规范降低10dB我检查了其他E4408B中的RYTHM
并且工作正常可能是A7A4（FEA）的问题？



     以下为原文

  I have a E4408B apparently with a flatness failure in high bands

The instrument completes the power on routine and performs the auto align without any problem.
Low Band works fine.
High Bands (from 1 to 4) have an attenuation of 10dB aprox in all frequency above 3GHz

Using the service manual, I checked the state of A8, RF Attenuator and RF in connector. They are fine.
But, I suspect of LOIS (A8A4), RYTHM (A8A6) and A7A4 (FEA).

The amplitude of the LO of LOIS output (A8A4J2), is 3dB down according with the service manual specification
The IF output for High Bands, from RYTHM (A8A6), is 10dB down according with the service manual specification

I checked the RYTHM in other E4408B and works fine

Could be A7A4 (FEA) the problem?