all numeric keys are working but 4,5 and 6 keys are not working in PSG Signal Generators E8257D
It sounds like the the connections for those particular keys are open. This is physical damage. It cannot be fixed without a technician opening up the instrument.
At the bottom of this page are some repair options for your instrument: Calibration and Repair Options
Here is some information if you want to learn more about Keysight Repair Services: Keysight Repair Services
Hope this helps!
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