E4436B显示器装置不正常

我刚买了一台带有选件UND，100和H99的E4436B。
卖方将其描述为“收到不良信号”，但无法提供任何进一步的细节。
当它到达时，它看起来已经得到了很好的照顾，带有2006年的校准标签。我打开电源并注意到显示器有一系列深色垂直段，如栅栏，但除此之外该装置似乎正常运行
。
当我移除前面板以研究显示器时，我发现从显示器到主板的部分插入带状电缆。
重新插入它修复了显示问题，但是，其他发现，如输出连接器上的松散SMA连接器，缺少的螺丝和松散的电缆夹，表明有人曾经在其中。最初，我注意到这一切似乎都是错误的
与输出是它下降约0.5分贝，并没有考虑到一个严重的问题。
然而，当我开始查看E4402B上的各种频率时，我发现在2 GHz时，相位噪声非常严重，以至于根本看不到峰值，并且相位噪声在两侧几MHz都会传播
承运人
以下是我认为很奇怪的部分：当我将输出从2.000 000 000 00 GHz调整到2.000 000 000 01 GHz（上升0.01 Hz）时，相位噪声完全消失，信号看起来很完美。
此外，当我调到低于1.990 GHz时，信号看起来很好。
我还没有调查过所有其他范围。
在2.000 GHz和1.990 GHz之间的范围内，相位噪声随着频率的降低而降低，我在SA上看到的是在载波两侧随机出现几个MHz的短暂，离散尖峰，变得不那么频繁且不太明显。
频率降低。我对ESG系列基本没有故障排除经验，所以我很感激任何建议。谢谢，斯坦



     以下为原文

  I just acquired an E4436B with options UND, 100, and H99. The seller described it as "gets bad signals" but could not provide any further details. When it arrived, it looked to have been well taken care of, with a cal tag from 2006. I powered it up and noticed that the display had a series of dark vertical segments like a picket fence, but otherwise the unit seemed to operate normally. When I removed the front panel to investigate the display, I found a partially inserted ribbon cable from the display to the motherboard. Reinserting it fixed the display problem, but that, and other findings  like a loose SMA connector on the output connector, a missing screw, and a loose cable clamp indicated that someone had been inside it before.

At first, all I noticed that seemed wrong with the output was that it was down about 0.5 dB, and didn't consider that a serious problem. However, when  I started looking at various frequencies on my E4402B, I found that at exactly 2 GHz the phase noise was so severe that the peak couldn't be seen very well at all, and the phase noise spread for several MHz on either side of the carrier. Here's the part I think is weird: When I adjusted the output from 2.000 000 000 00 GHz to 2.000 000 000 01 GHz (up by 0.01 Hz) the phase noise went away completely and the signal looked perfect. Also, when I tuned to less than 1.990 GHz, the signal looked fine. I haven't investigated all of the other ranges yet. In the range between 2.000 GHz and 1.990 GHz, the phase noise decreased with decreasing frequency, and what I saw on my SA was randomly occurring brief, discrete spikes for several MHz on either side of the carrier, becoming less frequent and less apparent as the frequency was decreased.

I have essentially no troubleshooting experience with the ESG series, so I'd appreciate any suggestions.

Thanks,
Stan