I was considering buying a MTH Pan Am F-7 A-B (Power -Dummy) when I realized that I was buying 2 different units now for a total of about $600. The new deal has no"tether". A year or so ago you could buy an MTH A-B-A (Power_Dummy_Power w tether) for $695. I have a 2005 Lionel TMCC steamer w/o a tether. Everything works as it should.
I've bought some MTH & Atlas lately and notice that the quality has slipped, i.e. new Premier Passenger car with missing step and new Atlas Boxcar with a broken coupler Prices seem to be going up and quality is going down. I hope that the MTH Genset I have on order comes through OK. I've had better luck buying USED lately. I may consider only going that way and let someone else filter the quality.