I needed a supply to power my Wireless #19 set. I tried an unregulated supply from Poly Paks. As the dynamotor rev'd up the rectifier diodes exploded. I then rewound a large TV power transformer for 12 volts out, mounted four Poly Paks stud rectifiers on heat sinks and used lots of filter capacitors. Back in the days that did the trick.
"I bought at an estate a 24 DC 3.4 A regulated supply. I bought it because "it was dirt cheap", which actually is not actually a good reason.
Is this supply enough to power a receiver dynamotor, considering start-up inrush ? "
The receiver motor you have will probably take at least an 8 amp supply to handle the surge, but, if that estate supply is just a simple supply with no over-current shutdown, it may sag but not cut off and get the motor to turn, and as the supply recovers as the current drops with motor speed, run it fine. My experience with a BC375, ART13/DY17, UT6A, BC348, and SCR274 all running on dynamotors, a minimum of double what ever the manual specs as what the supply should deliver.
I think most folks just run a pair of car batteries in series for those big loads with a charger in place to keep things up to snuff, but with the price of batteries today, a big enough switcher supply is more affordable. A 24 volt supply is usually cheaper than a 28, sometimes by a lot, and you can adjust them up to about 26.5, no real reason to run 28 as there was only 28 when the aircraft engines were running, 24 when not. Meanwell supply's are very radio quiet.
Charlie, W4MEC in NC