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There can be a few reasons for dim displays. If the display is uniformly dim all over then a common cause can be dried out (high E.S.R.) capacitors that are often used to derive the specific voltages these vacuum fluorescent displays use. The displays themselves can also become low emission but that often shows as some segments as being dimmer than others. You would have to post the relevant diagrams for us to identify any possible problem caps.
Also the display and the window can attract dust and grime and that also reduces light output.
There can be a few reasons for dim displays. If the display is uniformly dim all over then a common cause can be dried out (high E.S.R.) capacitors that are often used to derive the specific voltages these vacuum fluorescent displays use. The displays themselves can also become low emission but that often shows as some segments as being dimmer than others. You would have to post the relevant diagrams for us to identify any possible problem caps.
Also the display and the window can attract dust and grime and that also reduces light output.
Does the display really look like it does in your picture with thoe segments missing on the graphic equaliser? I ask because the display is multiplexed and its possible for camera artefacts to play a part.
If those segments really are missing/dim then that is not a normal fault and it could be either the display or the chip driving it. It would be a very unusual fault.
Is there any change if you apply pressure to the display driver PCB?
If those segments really are missing/dim then that is not a normal fault and it could be either the display or the chip driving it. It would be a very unusual fault.
Is there any change if you apply pressure to the display driver PCB?