有故障的34410A

我的34410A万用表有问题。
在某些范围内，它适当地测量，在一些范围内具有一点偏移。
我试着校准它。
它通过了ADC校准，但未通过DMM校准。
我得到错误707校准错误：在第一个DMM校准步骤中信号测量超出范围，这是零调整。
我进行了自检并得到错误623 ADC Mesure Zero Overload Test。
服务手册中未提及该错误。
我试图修复它，但如果没有万用表操作的原理图和知识就很难。
我检查了所有可能的组件，它们看起来很好。
是否有可能获得与导致该错误的电路相关的34410A原理图的至少一部分或某些故障排除提示？



     以下为原文

  I have a problem with my 34410A multimeter. In some ranges it measures properly,
in some with a little offset. I tried to calibrate it. It passed the ADC calibration but it fails
the DMM calibration. I get error 707 Calibration error: signal measurement out of range
in the first DMM calibration step which is zero adjustment.

I ran a self-test and got error 623 ADC Mesure Zero Overload Test. That error is not
mentioned in the service manual.


I tried to repair it  but it's difficult without a schematic and knowledge of the multimeter
operation. I checked all the components I could and they seemed to be fine.
Is it possible to get at least a part of the 34410A schematic which is associated
with the circuitry causing that error or some troubleshooting tips?