4192A LF阻抗分析仪无法排除故障

我有一个HP 4192A有一个我无法排除故障的异常问题。
当我上电时，设备通过所有自检（01-06）并在显示“A”上显示“PASS”，显示HPIB的十六进制地址，然后显示“A”和“B”变为空白。
手动自检（蓝键和6）也通过。
自动运行不起作用（即，触发灯不会自动闪烁，并且在任何内部测试点上都没有自动触发）。
前键盘的手动触发器将闪烁触发灯，但不显示“A”或“B”上的数据。
如果在前面板上选择了平均功能（蓝键和4），则触发灯将使用手动触发保持4倍，正常功能4192A。
所有显示元件和LED在自检时都亮起稳定且牢固。
所有前面板键输入都显示正确，LED指示灯应答。
我按照第8-36页的定时说明中的服务手册中的建议更换了A6U33，但没有变化。
我可以从HPIB接口发送命令和接收数据。
我很确定（但不是正面的）A6电脑板和显示板正常工作。
振荡器稳定而准确，可以从前面板和HPIB进行控制。
偏见也响应命令。
我用数据探针检查了小数N芯片的输出，并输出了数据。
右上角的频率显示正常响应所有输入（频率，偏置，振荡器电平）。
看起来该单元无法完成测量，将其数据提供给显示器并启动另一个触发序列。
任何有关如何从这里取得进展的想法将不胜感激。



     以下为原文

  I've got an HP 4192A with an unusual problem I haven't been able to troubleshoot.  When I power up, the unit passes all the self-tests (01-06) and says "PASS" on Display "A", shows the Hex address for the HPIB and then the Displays "A" and "B" go blank.  The manual self-check (blue-key & 6) also passes.  The auto-run doesn't work (i.e., the trigger light doesn't flash in auto and no auto triggers on any internal test point).  A manual trigger from the front keyboard will flash the trigger light, but no display of data on "A" or "B".  If the average function is selected on the front panel (blue-key & 4) the trigger light will stay on 4x longer with a manual trigger as with a normal functioning 4192A.  All display elements and LEDs light up stable and solid on the self-test.  All front panel key entries appear correct and LEDs respond as they should.  I replaced A6U33 as suggested in the Service Manual under Timing Notes on page 8-36, but no change.  I can send commands and receive data from the HPIB interface. I'm pretty sure (but not positive) that the A6 computer board and Display board are working normally.  The oscillator is stable and accurate and can be commanded from both the front panel and HPIB.  The bias also responds to commands.  I've checked the outputs from the fractional N chip with a data probe and there's data being output. The Frequency display on the upper right responds normally to all inputs (frequency, bias, oscillator levels). It appears the unit is not able to complete a measurement, get its data to the displays and initiate another trigger sequence.  Any ideas on how to progress from here would be greatly appreciated.