[Eeyore]

wrote:

My advice is to make a solid state plug in with diodes and two
resistors so as to drop the B+, as the Quad PT is giving pretty much
all it's got even without the load of the five volt winding if the
tuner or preamp are run off it.

I thought, How would you put a delay in there as part of the plug in
device without adding a ground or external sense connection? It could
be done, you'd need some sort of relay and timer circuit.

Here's an idea.

Use a large value series R so the Cs charge slowly. Connect the relay coil
( 48V ? ) to the B+. When the voltage reaches the pull-in voltage of the
relay it shorts out the high value R leaving a lower value which you would
wire in series with the high value one. Cheap and easy.

Graham