Dear Forum,
I have a MRC Cab Control 77 Throttle I purchased new many years ago right before I disassembled my layout to make room for kids, job re-locations, etc., and it is still new in the box. It was one of the first to offer pulse control, as I recall. Do any of you have any experience with this unit, and is it safe for modern n-scale engines? I have a few older can-motor equipped units as well. I have been very hesitant to use it since in my one and only trial those many years ago it launched a Kato PA-1 off the end of the layout at near light speed. MRC replaced it under warranty, but it does make one skeptical.
Thanks in advance for any insight you can give.
Cordially,
Paul
That's kind of funny. I feel sorry for the engine. It reminds of me of the little comic they have at the back in MR a few months back where the character has the smae problem. By the by, what is "pulse control"?
Is that the transistor one or the rheostat one? I never can keep all those things straight. If it's a rheostat type and it's NOT the 'N' model (like they had a model 501 power pack for H and a 501N for N) then it will not control your locos - heck it won;t control modern HO with quality can motors. N scale (and HO) with quality motors draw so little current that no voltage gets dropped by the rheostat so the pretty much go from stop to top speed with no control. If it IS an N model, or if the 77 is the transistor cab control, it should be fine.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Dear Randy,
I believe it is transistorized; at least that is mentioned on the outer packaging. I will need to double-check the documentation to determine just what that means in real terms (ever the skeptic, I suppose). I have become aware - at least peripherally - of the debate over pulse DC vs straight DC, and since I am restarting with basically a clean slate I am trying to "get it right" the first time.
Thanks for your response.
I suppose it is a testimonial to the quality and robustness of the Kato mechanism that the only damage suffered was a broken coupler. I was really surprised that it didn't cause any misalignment of the gear towers.
From what I understand, pulse control is/was a method of improving low speed in DC throttles by either halving the waves in modulated(?) DC, or by injecting a pulse waveform over straight DC. In theory, the short "pulses" kick-start the motors, overcoming the cogging effect of open-frame motors. Again, in theory, these pulses could also cause over-heating in the motors, or damage to the brushes/commutators (if these terms are correct).There seems to be some debate over the veracity of the latter statement. My apologies for what I'm sure is an over-simplified and possibly erroneous explanation; this is not my particular area of expertise.
Paul,
Early DC throttles used 1/2 wave(pulse power) to 'kick' the motor. And you could hear them 'buzz' at times. More sophisticated throttles stated using Pulse Width Modulation(PWM) so you could automatically ease to full power smoothly. DCC throttles/decoders basically use the same theory as well. One of the issues with old fasioned 'pulse power' was that it could overhear/destroy a sealed 'coreless' motor rather fast.
In the past 20 years, low current 'can' motors have replace the old open frame 'Pittman' style motors in many HO engines. The current drew is much less. A typical open frame motor can draw at least .6 to .75 amps of current. A typical 'can' motor may draw on .25 amps of current. Some folks will tell you that the old Athearn motors draw 1-3 amps of power. They can pull that much current, but adjusting the brush spring tension will do wonders. I would test my new Athearn engines and after cleaning up the drive train and adjusting the brush springs, I would usually wind up with them drawing only a little over 1/2 amp. Good luck with you old throttle!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
A google search brought up this thread (http://66.39.158.142/Forums/viewtopic/t=5093/view=previous.html) on another forum with an advertising picture of the box. The unit is a fairly sophisticated transistor throttle in a walk-around box. Ciricuitry is advertised as quad op amps and ICs. Features include variable pulse frequency, brake, momentum, etc.
In generic terms, MRC throttles did not use aggressive pulse control schemes that some competitors did. As a result, I never heard any reports of overheating on MRC pulse control. The motors most susceptible to problems with "spikey" pulses were/are coreless motors and some early can motors ('70s to '80s era), and those were primarily with low frequency, 12-16 volt pulse sequences at the mid-speed ranges. Modern N scale engines use DCC decoders that provide pulse width modulation, but at much higher frequencies than 60 Hz. So the expectation is there that the motors will see pulse control.
I would be very surprised if you had any overheating problems caused by using the MRC throttle. To be ultra-safe, you could keep the pulse frequency setting at the high end.
As for the locomotive launch, I suspect throttle, momentum, and brake setting interactions could give control problems until well understood. I recommend keeping the momentum off until you can experiment and understand exactly how much momentum you will get at various settings (and what the brake will and will not do at each setting). Momentum isn't necessarily easy to use on a small layout, especially in N scale where top scale speeds are in the 200 MPH range.
my thoughts, your choices
Fred W
Thanks so much to everyone who responded. This unit has been in storage for over 20 years, but seemed to function properly when I hooked it up to my test track. Hopefully it will continue to do so when I finally try it on the new layout.
Speaking of the new layout: I am in the final design stages for a double-deck around-the-walls n-scale shelf pike built into custom bookcases in our den. Normally there will be one operator, and most trains will be at most two engines. Based on its size and and anticipated operating scheme, I can't justify DCC at this time. Considering this brief discription, would you perhaps have recommendations for a walk-around DC throttle, to either replace or supplement what I already have?
Thanks again.
A good option would be the Aristo Craft Train Engineer wireless throttle. I have done much work with it in HO and it is very good with all this new stuff. I can also supply you with some improved DC wiring methods to take full advantage of the walk around nature of the Aristo Throttle.
Sheldon
Just one or two more questions, if I may. I read the information presented in the link you provided, and it was mentioned there might be a "dried-out capacitor". First, if the throttle seems to work (I haven't tinkered with the momentum, etc.), would this necessarily indicate the unit's capacitor(s) are functioning? Or are the capacitors (judging from the description) only used by certain functions?
Second, does a "dried-out capacitor" recover with use?
This information is more to help me more fully understand electronics, so any guidance you can provide will be most appreciated. I realize there isn't much to go on, really.
Thanks once again,
Since the cab control uses DC input, the only capacitor in it is likely the momentum. A dried out electrolytic capacitor will not recover. Best case, it's fine and everything works as it should. Middle case, you can run trains fine but the momentum feature does not work - it acts like it's always turned off. Worst case, the failed capacitor causes it to not work at all, you turn the knob and the output doesn't increase. With a momentum circuit, it's pretty much impossible for the capacitor in it to fail and make the trains just take off at top speed. If the momentum circuit is broken, it won't make the throttle put out wierd voltage or pulses that would damage your locos.
Thanks, Randy.