Help request trouble shooting BHK250 issue

A request to PS Audio or any owners who may offer insight into this issue. My BHK250 amp functions flawlessly with my BHK preamp but I’ve only used it up to this point with balanced inputs. I recently reconfigured my system layout and installed my Dehavilland UltraVerve III single ended preamp. The Dehavilland sounds marvelous with the BHK250 but after it’s been operating for 45-75 minutes something happens that sends the BHK250 into the flashing blue light fault mode. If I turn everything off and on again, the combo operates fine for a while and then the fault mode gets tripped again. I don’t have a tube tester but I’ve replaced every tube in the Dehavilland with NOS or previously used tubes I know worked fine in previous situations and the issue continues. My dilemma is whether there’s a specific incompatibility between these components, or is there something awry in the BHK250 single ended input, or some intermittent fault happening in the DeHavilland (and will DeHavilland be able to diagnose it?) The DeHavilland has a ground lift option but I haven’t tried that yet, not sure if that could affect the problem. I also have another single ended preamp I could install but it’s a real PITA to remove and reinstall from that system so I thought I’d see if anyone has any insights before trying that. Thanks!

It seems to be a component problem. The RCA’s either work or don’t.

vaguely possible the new single ended source has some ultrasonic oscillations/instability going on.

is the bhk especially hot when it shuts down?

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It’s possible that the pre is sending something to the amp that is putting it into protection mode.

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So, if I sent this back to DeHavilland for Kara to trouble shoot, any ideas as what sort of electrical gremlin “somethings” the preamp could be sending to the amp that puts it into protection mode? What faults trigger protection mode exactly?

Check your speaker wire to make sure you are not getting a short.

I don’t want to speculate too much but the amp will shut off if it detects DC on the input. That is just one example of what could be causing it.

Thanks. I’ve checked all speaker wires and changed interconnects to make sure that’s not the issue.

I’ve written Kara @ DeHavilland, I’ll see what she says. I just wanted to tell her the possible situations that would shut down the BHK to aid her troubleshooting.Thanks for the quick reply Jamesh!

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