How To Set DC Reject As Default - Model 2430?

Greetings and please accept my apologies for such a fundamental question but I am an old analog guy who never wants to measure DC with my Model 2430.  I am long retired and just like to build, modify and repair old tube/valve gear.  For example I want to be able to view audio frequency signals on output transformer primaries that may be riding on 500vdc.

I bought this Tektronix 2430 used after my even more ancient analog scope died after decades of service.  Do I need a specific probe or can I set this model to default to measuring AC signals only.  I see a trigger mode set that will allow me to set to AC as well as a "LF Reject" but neither allows me to view AC signal riding on DC.  The trace just leaves the screen.

Obviously I could jury rig a 600v capacitor in series with the probe but that seems Rube Goldberg clunky.   What do I need or what am I doing wrong?

Hi James,

As it says on the front panel of the 2430, the max input voltage is 400 V, if you connect a signal with 500 Vdc you risk damaging the instrument.
Page 1-6 of the manual reinforces this and specifically says this is also true for AC coupled mode.

The trigger LF Reject mode only applies to the trigger path, it does not affect the channel acquisition path.

So, the 2430 does have an AC coupling mode, but your DC offset is so high that you risk damaging the instrument if you use it directly. Instead, you should use an external DC block (which is just a capacitor in series) rated for 500 Vdc before the channel input.