Kevin, there’s a screw in the base of the handheld unit which can be used to adjust the momentum feature - I don’t care for momentum either, so mine is turned off.
There’s some discussion here about generation of heat, but the portion of this throttle which is to be installed under the layout is equipped with a large heat sink. As I mentioned, I’ve run over a dozen locos at a time, and also multiple locos on trains which weighed over 20lbs. and had no problems whatsoever. Ken also stands behind the stuff he builds, and I’m very pleased with mine.
the irony is that the throttle has to dissipate more heat at low, rather than full throttle settings in a linearly regulated throttle as shown in the schematic.
when the locomotive is operated at a high voltage, 10V for example, and drawing 1 amp, the locomotive is drawing 10W (10V x 1A). If the supply is 12V, there’s 2W ((12-10V) * 1A) of heat dissipated in the throttle.
but if the loco is operated on 2V and let’s say 0.5A, the locomotive is dissipating 1W (2V * 0.5A) but the throttle is dissipating 5W ((12-2)V * 0.5A).
this is the beauty of PWM. The throttle either provides max voltage on no voltage, on-off. The MOSFETs in my throttle have an on resistance of 0.04 Ohm, so when on and providing max voltage, they disspate 0.04W of heat when passing 1A.
And that is exactly why decoders all use PWM. There is no room on a decoder (or in most locos) for a heat sink or even a component large enough to handle a watt or more of heat (most HO decoders are rated for continuous 1-1.5 amps, and momentary peaks to 2 amps). By using PWM, even a small surface mount component can easily handle the limited amount of heat generated.
i happened to see a product review for the MRC Tech II models 1400/1500/2400/2500 in RMC, i believe march 1980. It showed scope traces. Those traces showed rectified AC. A switch on some of the models controlled whether it was half or full wave rectified.
WIsh I still had my 1500 to test, or open up and look. I don’t think the circuit was that complex. They were simialr to earlier designs that produced a sine half-wave pulse when the throttle was cracked but as the throttle was increased it either filled in the other half or lowered the level of the pulses (take your pick - the effect is about the same, stronger pulses on startup with little or no pulses at full throttle). Most of the “tech speak” on the packaging and on the units themselves was marketing fluff. Mine worked well, and was a big improvement, but considering what came before it was a simple Aurora Postage Stamp Trains power pack, anything would have been better.
I do have a Tech IV, and I have a set of pretty much every security blade screwdriver bit known to man, so unless they glued it all together, I should be able to take a peek inside. Kind of curious now. I’ve only used it to run some HO locos back and forth ona test track, and it does have nice smooth control but the locos are an Atlas/Roco S2 and a custom painted BB SW remotored with a Sagami can motor so darn tootin’ they run smooth.
the may 1980 RMC completed the review of the 1500/2500. It had described the 1500/2500 as having momentum/brake and the 2400/2500 as higher powered versions of 1400/1500.
but the 2500 uses PWM unlike the other 3. The review showed scope traces for the 1500/2500 at 4 throttle settings. PWM pulses are ~16 msec apart, which is the period of 60 Hz. I could see some 60Hz ripple riding on top of the wider PWM pulses.
the article discusses motor heating as a disadvantage of PWM, which it probably is at 60 Hz. I believe modern day decoders use processors that can generate PWM pulse at 200 kHz.
This is because Rapido outright says in their product manuals that they have had damage from customers using these two power packs (as well as trainset powerpacks). Rapido also says, in the same sentence (paraphrasing) that they will not replace the circuit board in the locomotive if you damage it in this way. No idea if they are serious or just messing around (its kinda hard to tell with them), because I dont run DC. I have an MRC Tech II 2500 (I think) for break-in and testing of repairs prior to decoder installation.
I know Jason likes to joke around but if they come up with an issue that is shown to cause damage to the locos I doubt that is one of their jokes. Those cheap power packs aren;t well filtered, and they could easily be putting out spikes far higher than the moninal 12 volts - it doesn’t necessarily cause problems with the motor (except maybe a coreless motor like in those Kato locos with the truck mounted motors), but with dual mode DC/DCC electronics it could cause components like capacitors to charge up above their rated value and fail.
I do also have a 1370 I got to do DC testing, I should take a look at that along with my Tech IV. If I remember to take it home from work (I used it to run large scale Thomas around the office tree).
