The 760 puts out noticably higher voltage than the 780 with the throttle at the same relative position in the range. This is obvious when starting up DCC with sound locomotives.
But surely it cannot be delivering 21v to the motor or the decoder at full throttle.
It does deliver a no load 21v as measured by multimeter.
Does MRC760 somehow use a bemf measurement to allow a higher effective net voltage to reach the locomotive motor but not exceeding the 12-14v design voltage for that motor?
Put another way, can the MRC760 push current into the motor at safe net voltage but using a higher voltage output capacity than the MRC780 does?
Locomotives run better, pull better, when powered by the MRC760 than when we use the MRC780 even for the same locomotive run in the same block of track.
The MRC760 also has optional momentum delivery which is pretty good for DC only locomotives although not adjustable.
I think part of this is that the 760 and 780 have the same power rating (20VA) so what you have is a unit that can go to ‘higher voltage’ for larger-scale equipment.
The same general argument might be made here as was advanced in the Firestone 721 tire litigation, a subject Mike might know well. Just because your speedometer goes up to 120mph does not imply the vehicle should be driven up to that speed… let alone around corners at that speed. Likewise most eequipment would likely be at terminal speed long before you got to the first overvoltage failure point.
Perhaps the additional voltage ‘headroom’ is useful to the Accutec ‘feature’. It seems a bit disingenuous to market the 760 as ‘suitable for HO, N, and Z’ without mentioning peak voltage limits anywhere in the manual or providing any over voltage protection if, say, a sleeve or a cat were to pull the throttle knob fully open by accident.
We’ve run both DC and dual mode decoder DCC locomotives at full throttle using the MRC760 without apparent problems.
I have not tried to measure actual locomotive speeds to see if there is no increase in speed after a certain point on the throttle range.
My LHS guy assured me that the MRC760 is safe to use. I also wrote to Rapido due to their dire warnings about some older DC powerpacks and they assured me the MRC760 would be safe.
I’m wondering how the unit limits output to a safe voltage given the rated capacity.
I’m not sure if I’m standing in the same ball park as you two on this topic, but my Digitrax DB150 has a toggle with three positions, one each for N, HO, and O scale ops.
About then years ago, I glanced at that toggle and saw that it had been flipped up to the O position. No idea how long, but I can tell you I had operated several different locomotives in HO before I noticed the error. No apparent problems. I have only ever replaced two decoders, and then many months after this incident.