HP4194A分析仪无法POST

我目前有一台HP4194A分析仪，它运行良好，直到有一天关闭。
在关闭它时它不会再次打开。
后面的风扇将运行，屏幕将打开但不显示任何内容。
前面的两个LED保持点亮位置以及两个处理器板A6和A8上的所有POST灯。
但是，任何一块电路板上的总线停止LED都不亮。
以下是我作为问题的建议解决方案所做的事情列表。
所有电源板和处理器板上的盖子都已更换。
已检查所有电阻值的板A3，A6和A8的公差。
检查所有电压/频率并将其重新调整到服务手册规定的正确电压。
服务手册流程图也引导我走向死胡同。
我相信罪魁祸首绝对是A6-A8板。
在检查来自电源监视器的暂停线之后，处理器也接收正确的电压。
如果有人对这些机器有任何重要经验并遇到类似问题，请分享您的经验。
谢谢！



     以下为原文

  I current have an HP4194A Analyzer that functioned fine until it was turned off one day.  Upon turning it off it would not turn back on again.  The fan in the back will run and the screen will turn on but display nothing.  The two LEDS on the front remain in the lit position as well as all the POST lights on the two processor boards A6 and A8.  However, the bus halt LED is not lit on either of the boards.  Here is a list of things that I have done as a proposed solution to the problem.

The caps on all the power supply boards and processor boards have been replaced.  All resistor values have been checked for tolerances on boards A3, A6, and A8.  All the voltages/frequencies have been checked and readjusted to the correct voltages as specified per the service manual.  The service manual flow charts also lead me to dead ends.  I believe the culprit is definitely boards A6-A8.  The processor is also receiving the correct voltages after checking the halt lines from the power supply monitor.

If anyone has any significant experience with these machines and has experienced similar problems please share your experience.  Thanks!