Sleeping mode in 335

The issue you are reporting is not a feature that is in the Model 335, therefore, so other problem is causing the screen to go blank and the GPIB to stop working.

The only thing we can think of that would affect both the display and GPIB Interface would be an issue with the AC input to the transformer.

I recommend doing the following:

1. Check that the AC Input Voltage selection is correct for the voltage you have connected.
2. Remove the top cover and verify that all of the connections from the Transformer to the AC Input Module are tight and that the secondary connections from the transformer to the Main PCB are not loose.

If everything is good in the Model 335, possible switch the AC inputs between the 335's and see if the issue remains or moves to the other 335. If it moves, that indicates that your AC connection has an issue and may be dropping below the minimum voltage for the setting you have. If it remains on the same 335, then there is possibly an issue with the transformer or some other power section on the 335.

One you complete the verification and AC input change, let me know the results by sending an email to support@lakeshore.com and we can determine what is required to resolve the issue.