The DGC III ion gauge control is used on many of the older PHI (Physical Electronics) surface analysis systems. Sometimes the DGC III fails to operate properly, and the unit will beep and display 0.0-3

There are several possibilities for this issue;

The filament may be open. This blog post shows you how to test for that – https://www.rbdinstruments.com/blog/how-to-test-an-ion-gauge-filament/

One or more of the voltages on the power supply board (+/-12, +5) may be defective. This PDF file shows how to test for that –

Some other things that you can check include –

If none of the above things solve the issue then most likely one of the other boards (emission, microprocessor, electrometer, set point) is bad. Troubleshooting those boards is more challenging so typically if the problem is not the filament or power supply board then the unit is set to RBD Instruments for repair. To contact RBD you can create a ticket here –https://www.rbdinstruments.com/support/portal.html