For any give DCC system, with a track voltage of X, pretty much all decoders should give a function output voltage of X - (the same amount), since the first thing in, the DCC track power hits a full wave bridge rectifier and other than that there is the diode drop of the controlling transistor for each output (input, since it's a switch to ground). There are exceptions, like decoders that come with constant current sources or resistors already in circuit to limit current for LEDs, but there's veyr little variation in the actual circuitry from vendor to vendor - the biggest differences are in the firmware of the microcontroller. Voltage to the motor at full throttle, assuming no modifications (CV5 at the default, for example) should be just a few diode drops below the track voltage to account for the rectifier and the H bridge drivers.
Your 179 should be giving accurate track voltage readings, but not all RMS meters will, not even all Flukes with True RMS - they don't all go up to 100KHz, though my old 8060 and my 45 benchtop meter both do. My even older 8012A only goe to 50KHz, but from 20KHz to 50KHz the accuracy is only +/- 5% + 3 digits. To 10KHz it's +/- 0.5% + 2 digits, quite respectable for something from the late 70's/early 80's.
Glad you got it all sorted out. A reset on some of those other decoders should get them performing more like they shoud. I will usually do a reset as the first step in installing a new decoder - just in case. It's not unheard of for some settings to be really scrambled from factory testing or because a decoder may have actually been a return. Some systems also have a decoder reset in the throttle programmiung menu. Digitrax doesn't, NCE does, dunno about MRC. The problem is, this is usually specific to the manufacturer's decoders - the NCE reset, for example, doesn;t use a CV to execurte a reset (there's no standard for that - though all decoders from a given manufactuer usually have the same method), it simply programs specific CVs to what would typically be the out of the box default values - except it sets some CVs that are specific to NCE decoders, so if you would try that on a different brand decoder, you'd end up with Address 3, and no momentum and so forth, but it might also set some CVs that do different things than the same CV in an NCE decoder. Best to use the decoder specific reset when available. The most common are CV8=8 or CV30=2. Some hedge their bets and support both options.
--Randy
Modeling the Reading Railroad in the 1950's
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