DCC Trains vs DC Power Packs. Or more "Rapido vs MRC problems"

[$2 Bill]

Relative to Railpower 1300 testing https://www.therailwire.net/forum/index.php?topic=44170.0 , https://www.therailwire.net/forum/index.php?topic=44120.0 , etc.
I recently bought a Railpower 1300 at a Flea Market cheap to connect to my old Tek 545 (Vacuum Tubes and CRT screen O-scope) to get a trace as a "base line" and did but unit died during testing.
But the Brief Trace shown about 20v Peak before it died. (Saw a good trace but died before get a meter on it or a camera.)

My take-away from this is that N scale decoders are designed to utilize square waves up to about 14 volts, and that pulsed DC controllers provide peak voltages above 20 volts, so I am not going to put my decoders from any manufacturer on any DC controllers from any manufacturer, at least until I have actually measured peak voltage output and found it to be under about 16 volts, preferably under 14 volts.

I have more "Bad News..." While he said N but many DCC "Black Boxes" for other scale trains and other thing many have problems running on many DC power packs not just MRC "Pulse" units...
Since I have more Power Packs, I tested several other units and most of them have Peak Volts > 16v
Load: 120ohm 15w Ceramic shell Wire wound Resistor. 20V x 0.16A= < 4W. Resistors to remove Noise from other loads like motors.
O-scope: Tektronix 545, 10x Probe, 0.5/Div=5/Div to read Peak.
Meter: Craftsman Pro 82003 True RMS meter Auto Volts set itself to DCV
Mod   Peak   Meter
1400   18   13.45
2500   14   15.23
Bach   18   14.58
Tyco   18   15.55
MRC Tech2 1400 has custom 4 pin "Speed" POT that injects the Pulse on the 4th Pin but works similar to 1300 and many other MRC units for voltage testing. Because of the 4th pit POT the Traces for 1400 is Not the same as 1300 and others.
MRC Tech2 2500 is Not like many other power packs including most MRC products. This output "PWM" at around 15v and can't be measure volt except near or at full power. You can measure % of PWM but expect issues with meters that does this as doesn't seem to have 555 or other chip and have hard time to measure % at top or bottom. (I only get 8% to 88% before the meter say 00.)
Bach is Bachmann 6607 plastic power brick unit typical to cheaper current train sets. Rated for HO and N on the "label."
Tyco is Tyco 899BP Steel case power brick unit typical to cheaper older train sets.

I didn't test DC or AC accessory power terminals. They often will be Higher Peaks or RMS volts as AC just puts out "Raw" volts from the Transformer.

Warning: None of these and more have Nothing to Protection for Power Surges or Spikes. So when you have Dirty 120/240VAC Main Power, transformers will pass that crap to the low volt side that most have Zero Protection on that side too. Also nearly all won't stop Surges, Spike, or Static Shocks on the low volt side from killing DCC controllers and other electronic parts.

Many Current DC power packs use "Wall Warts" or other external packs that are mostly Switching Power Units that does protect low side from Line side Surges etc. in many cases But these units can cause problems DCC controllers as many output > 15DCV.

I also tried to test even older AHM 70203 Steel case power brick unit but outputs Half Wave trace is common problem when a diode is dead so not listed here.

No pictures because not reaching whatever minimum limits to post and not using imgur Youtube etc.

[peteski]

Welcome to the Forum Bill.
See https://www.therailwire.net/forum/index.php?topic=43673.0  and https://www.therailwire.net/forum/index.php?topic=42854.0

As for the DC power packs, I would not recommend using any of them for running decoder-equipped models.  Most of them are either very crude designs using only a serial connected rheostat, or have a basic bare-bones transistor circuit. As you mentioned, they have no over-voltage protection or even basic voltage regulator included.

Then of course there is the issue of some decoders being confused by the unfiltered pulsing DC voltage causing the decoder to misbehave.

Most smaller scale decoders usually have maximum voltage rating of 20V, but as you noted, there could be spikes present which could kill the delicate electronics on the decoder.

For testing decoders in DC I use a variable-voltage DC power supply which produces filtered and regulated DC voltage.

[$2 Bill]

You can use "lab" type or other adjustable PSU to test but the main problem here is many are using DCC trains in "emulation mode" running on DC Tracks for any reason like take a train to a friend with only DC. Many don't want or can't spend for DCC. I don't have DCC because very small layout and many engines to run and even then don't run them often. Others have DCC and DC equipment try to run both at home and fry the DCC board at minimum.

Is why Rapido and likely others can/will Void the Warranty...

After our 100th burned-out customer decoder caused by 1300-series power packs, we added the warning and stopped covering decoders killed by 1300s under our warranty. There are no issues with any other MRC products - just the 1300s. The 1300s burn out ESU decoders. This isn't an opinion. It's not a critisicm of MRC. It's simply a fact.
<Snip>
Similarly, if you use a trainset controller or one you built yourself, your decoder is not covered under the warranty. We've had people destroy a $350 locomotive with a 1970s Lionel HO trainset controller. These guys would never consider charging their iPhone with that transformer, yet for some reason they think model trains should be compatible with stuff that was cheap quality 50 years ago.

We try to make our models as backwards-compatible as we can, but it's just not possible to make a state-of-the-art, sound-equipped model from 2018 work reliably with every DC controller ever built from the 1930s to today.

Because Many made and still make all kinds of DC controllers and now use Eflay AliEx etc PCM modules to run DC Trains can still fry DCC plus also using Dell, HP and more PSU "Bricks" from old Laptops etc that often output 19+ DC Volts. Even tho PCM controllers was "easy" to make 30+ years ago, now anyone can buy one and stuff whatever parts together without a clue can be bad even for DC trains.

But Even when you have a DCC power box controlling DCC trains... Many don't have much protection for crap power. DCC companies often uses "Wall Warts" and other power packs made in china or now other 3rd world countries made to be very cheap even when has Valid UL Marks etc.

So in very brief anyone not using good surge protection is gambling when not if a surge or spikes on 120/240 side is going to fry things. (240ACV is mains power in EU, UK, etc.) For North America... Even if you have surge protection that NEC now requires for new or rebuild systems in breaker boxes, these Type 1 or 2 units are often setup for 700+ Volt surges from outside your home. It does very little for surges or spike generated from AC, Refers, etc in a home. You want local plug strips etc that stops 330v surges for 120v RMS AC come out of outlets. All Plugin units are Type 3 but Surge Volt rating can be higher then 330V and worse only protect Line not Neutral.  "Good Unit" typically read L-G N-G 330V L-N 400+V is so most Surge/Spike Volts are force to Ground Before get to anything downstream.

Where you have static shock hitting tracks etc... is often much harder to protect DCC and other electronics. Spray anti-static on carpet etc may help but doesn't last long.

Seen both pic threads... No hurry to post 25 times so click add pic = "You are not allowed to add a picture." Admin has remove "standalone" pic/docs and Most others don't read the ToS etc on "Free" image hosting like imgur or youtube, farsebook.... So can insert img tags in a post but are useless.

[peteski]

The Rapido's warning was back 7 years ago.
I believe that in the 3rd decade of the 21st Century the odds of someone running a modern DCC-equipped loco using an ancient spiky power pack are so low that I would call it non-existent.  Most models can be purchased with or without a factory installed DCC decoder, so if someone is really still running old-school DC power, they have an option to just buy a model without a decoder (and save some money at the same time).

I'm not even sure why you brought this all up.  What is your goal?  To warn modelers against using old power packs with models equipped with DCC decoders?

[Point353]

The Rapido's warning was back 7 years ago.

What we never heard from Rapido was an explanation as to why only the decoders that they were using might be susceptible to damage from the output of certain power packs.  Only that those power packs could produce "spikes".  Not even a mention of the specific voltage level at or above which might cause damage.

I don't recall any other model train or decoder manufacturer issuing such an advisory.

[Maletrain]

People running DCC locos on "old power packs" is not so uncommon as you think. 

We see a lot of different people in our club, and even have 2 layouts in N scale -one DC and one DCC.  Some members have DC at home, but are "thinking about getting into DCC", so buy a DCC loco.  Then they want to run it at home as well as at the club.  I suggest that they don't do that, for the reasons that have been discussed in this thread. 

They do eventually tend to buy a DCC starter system, usually an NCE PowerCab or a Digitrax DCS52 or maybe even the Bachmann little gray box, to run at home with DCC.  But, it seems there is a transition period where funds available, indecision, or just procrastination creates a period of urge to run DCC locos on DC home layouts, some of which have ancient power packs.  And, "Why not?", considering the marketing about "dual mode" decoders.  It tends to make them think they can have "the best of both worlds" running DCC at the club and DC at home, "at least for a while".

[peteski]

While  I guess I'm not surprised you still see modelers using DC,  I am surprised they would be using the old-school rheostat-based throttles with absolutely no AC filtering or voltage regulations.  Those don't even give good low speed control with most modern models (and the AC component can confuse the decoder).  There are better throttles available if someone wants to run DC. 

Seems that if someone has funds to buy a DCC-equipped model, they theoretically should have funds for a better DC throttle.

As for this entire MRC 1300 kerfuffle, as it has been mentioned, Rapido never provided any specifics about the problem, and ESU (their decoders were in Rapido models) never issued any of those warnings either.   I think that if this was a wider spread issue, ESU would be warning their customers about the possible decoder damage.

[Point353]

People running DCC locos on "old power packs" is not so uncommon as you think. 

We see a lot of different people in our club, and even have 2 layouts in N scale -one DC and one DCC.  Some members have DC at home, but are "thinking about getting into DCC", so buy a DCC loco.  Then they want to run it at home as well as at the club.  I suggest that they don't do that, for the reasons that have been discussed in this thread. 

They do eventually tend to buy a DCC starter system, usually an NCE PowerCab or a Digitrax DCS52 or maybe even the Bachmann little gray box, to run at home with DCC.  But, it seems there is a transition period where funds available, indecision, or just procrastination creates a period of urge to run DCC locos on DC home layouts, some of which have ancient power packs.  And, "Why not?", considering the marketing about "dual mode" decoders.  It tends to make them think they can have "the best of both worlds" running DCC at the club and DC at home, "at least for a while".

The MRC 1200 Tech 6 is a dual-mode controller that can operate both DC and DCC locos.

[Sumner]

The MRC 1200 Tech 6 is a dual-mode controller that can operate both DC and DCC locos.

Same with the DCC-EX Command Station.  It has two track outputs standard that can be switched with your throttle between PWM DC or DCC at any time and run a DC train in one district and a DCC train (loco or consist) in the other district with the same wireless throttle at the same time.  There are options to go to 8 DC/DCC districts with the system.  Any of the districts can also be switch to Program at any time and/or you can also Program on the Main.

Sumner

[Doug G.]

Why use the cheaper packs, at all? For not much more money, you can get much more sophisticated DC packs on eBay. I have bought several MRC Tech IIs, Tech IIIs, Tech 4s, and Tech 7s with no issues.

Doug

[nickelplate759]

Well, I still have this:



It's an MRC 602 Variable Transformer, with DC rectifier.  Outputs are (supposedly) 16VAC and 0-12V DC.
It's over 50 years old, and it still works.  I bought it new way back when.

Yes, I've used it to test DCC models on DC.  No, that's not what I normally do - I have an NCE PowerCab for normal running. (I also have an old SPROG II, but haven't used it in ages) for DCC running - I use this to test (or run) DC models.

[Maletrain]

I have one of those old MRC power packs, too.  It had been unused since I "put the (HO) trains away" decades ago. 

When my wife wanted a tiny train to run under her new smallish Christmas tree, so that it would not stick out far enough to be stepped on, I went to the local hobby shop to buy an N scale train and some track.  The loco she wanted was a Bachmann DCC version 4-6-0, and the shop owner assured us it would run on DC.  So, we took it home and connected it to that old MRC power pack.  It would not run on that.  So, we went back and bought a Bachmann DCC controller, which could only handle 10 short addresses, and that worked.  (From there, my wife decided she likes model railroading, and is now using Digitrax throttles as a yard master at our club.)

So, my point is only that there are and will probably continue to be people who put DCC locos on track powered by old DC power packs.  Maybe not for long-term in most cases.  But, if it had worked for us, we would probably have used it for the first year, at least.

[$2 Bill]

Most DC and DCC Owners have No Clue and Don't Care about how many DCC things are "Picky" until something is "mostly dead or all dead." Even then many Will Blame the DCC parts makers saying made "weak" and worse and simple stop buying. This is not just "Rapido vs MRC" but those 2 "made the press" fighting about Railpower 1300. For every negative post here or anywhere else, you should expect Hundreds to Thousands more that "Hate" a product and never buy again. Many others just seeing the statements at their sites, here, etc and now see Red flags from both and not buy in the first place.

Worse, Many are told that DCC will run on DC tracks but most Stores/Sites never mention the possible problems making a sale like Maletrain. Often won't buy from the same place again. Many MRR, "hobby" or "toy"stores are gone partly because of "BS" statements by the owners or staff.

"Rapido needs to answer us..." Likely never going to happen. I work with enough Lawyers and Manufacturing to see that. Surprise many he have a few post on the topic here as maybe don't have Legal Dept or on retainer. Even ignore that, Rapido can write a Book about the problems they see alone but few will read and less will understand. Worse, many will bend whatever answers. My Guess even they don't have many answers and part of why stop posting in other threads for this topic. Then MRC panic and made crap statement and many seen right thru that smoke. Many have MRC Railine 300 and other models that's nothing but old Train Set "brick" with another case to see first hand no different but higher cost also are "UL tested."

Many think "old" DC Power boxes are the problem? Sorry No.

Much newer Bachmann and other new DC controller are made cheap too like Bachmann 6607 and other plastic power bricks still sold with many lower grade sets or as separate units.

Or many get Bachmann 44220, 44211 and other numbers In Stock at many shops and online have same Transistor circuitry in them and use simple 19VAC Transformer as localize Wall Wart to sell in EU UK or US. OEM Output rated at say 12-16VDC on train output but many are higher. While the "Guts" of these units may have better filtering etc.... The "Filtering" is for mainly reduces DC Ripple with 470-1000uf cap(s) but Surges or Spikes on input or output can blow thru that kill the controller and more.

Seem many think DCC controllers are safe... Sad news as Many are made "Cheap" too regardless of Final Retail Price.
Example: There are several reason many things use Wall Warts and other External brick but mainly they are already UL FCC and retailed Certified to save Cost for the Finish Product. Many of these bricks has very little or nothing to prevent Surges or Spikes on either side frying them or anything downstream. Again, UL etc doesn't = Quality but just Pass Testing for not burning down.

Is Why I said above all should be using a Power "Bar" with good Surge Protection. They have 3 wire input and outlets plus 3 MOV at minimum to prevent the Surges etc getting at DCC controllers and more. "Best" have "3 Mode" Surge protection also have other parts to limit/stop Electrical Noise getting thru too. Most/all Tripp-lite(Eaton) Isobar is like that. Some old models even limits noise between each pair of outlets but seems no longer made.

But All that's only starting to cover Surges/Spikes/Noise on the Mains...

The Tracks themselves and other low volt wiring regardless of AC, DC or DCC are a huge target for Surges, Spikes, Static Shock, and more problems like very few DC or "DCC Ready" Engines have anything blocking EMF generated by the motor when the power is cut. Some DC controllers have Flyback diodes like MRC Tech2 2500 to protect itself from the Trains! Same Engines would need more parts as DC power is reversible and Cost More to Make "for nothing" for them and most buyers to benefit even now. (Only Some current DC engine do have "Snubbers" for this.)

While DCC uses Differential Signaling to control a train... the controller or decode board can still have a lot of problems. Even if DCC have MOV TVS etc to limit low volt Surges/Spikes, RF problem can still make Decoders to have "fits" as Tracks and other wires act like Antennas. (And that's Even if DCC parts are FCC "Approved" under  Part 15 etc.)

Very often Static Shock Does Not = you feel or hear the shock. Even if controllers, boosters and decoders are protected.... You can easily dump 300-1000V touching the tracks etc in dry weather without you getting sparked. Repeated shocks etc can "wear out" many protection parts... Is why many Surge bars etc have light(s) to go out/on when MOV and other parts are "dead" or have mains with some types of problems. OW connected to mains with bad earth/ground.

[peteski]

Thanks for this very detailed write-up, but I still don't know what is the point of this thread.  Since pretty much everything can damage those very delicate and sensitive electronics in a DCC decoder should we just ditch the entire DCC thing and revert to DC powered models?  Or should we just abandon this hobby altogether?

Or should we spend thousands of dollars to buy an AC power conditioner for our layout room and then install anti-static floor or wear ground straps on our wrist while operating and handling out models?

Do your dire warnings also apply to all the smart phones being charged by those USB bricks plugged into household AC outlets?

Yes, there is some sarcasm in my post, but how far do we really take this?

[brill27mcb]

I run things on DC because most of what I run are N-scale trolleys, and most of them are from Japan, where DCC is still generally "off in the future." Then there are the Bachmann products which come with DCC built-in and offer no choice but to have it. My basic knowledge of power packs (vintage, newer, recent, "spike" pulses (intermittent and designed to get old open-frame motor designs to start turning), constant lighting and PWM (in general historic order) tells me that the only way to know what their true output is requires an oscilloscope, and a pretty good one at that. Some manufacturers choose not to reveal the details of their products.

My personal general rule is to avoid using the "vintage" old metal-cased power packs (like the one pictured in an earlier post). These they tend to have rheostats with a resistance designed around old HO open-frame motors, so they can't provide good low-speed control of smaller N-scale motors. Small old "set" power packs are even cruder and just have taps across the transformer windings, like old Lionel transformers.

"Newer" power packs, generally in plastic cases, have a transistorized power output which can provide good control irrespective of the DC motor type and size. Ones like the earlier Troller or MRCs use an optional overlay of "spike" pulses (not the same as square-waved PWM). I use them only if there is a Pulse switch and I can turn the pulse function off, since the max voltage of those spikes is often not disclosed.

Basic transistorized power packs, like the Kato S, are simply a transformer output, rectified to full-wave DC and amplified through a transistor. A small potentiometer is enough to control the output voltage. The Kato S puts out 15 volts DC max, but that's in the marked red zone of the dial; staying below the red zone keeps the output at 12 volts or less. The newer Tomix power packs that I also use have PWM, and the top voltage of the square-wave pulses is 12 volts. When the dial is turned up all the way, the pulse width is 100% and the average voltage then is 12 volts. The newer Kato SX is a PWM design. Outputs that are known not to exceed 12 volts DC should not damage DCC circuits.

I have seen oscilloscope traces from Japan for two type of the "constant lighting" (CL) feature used by Tomix. The earlier version, which can be identified by having a separate CL dial, provides a steady DC voltage, which can be adjusted to a level where the lights light but the motor does not yet turn. This is overlaid with a variable PWM voltage to control the motor speed. You can think of it as a PWM output where the "off" periods between pulses are a lower "constant lighting" voltage instead of zero. The later Tomix CL power packs simply have an outer ring on the throttle dial that can be set to physically block the main dial from being turned all the way down to zero. This sets a minimum PWM pulse width, enough to light the lights but not to turn the motor. These, too, do not exceed 12 volts DC. I have not had any DCC-equipped locos damaged by my Kato and Tomix power packs.

My understand of DCC is that something like 15 volts is needed on the rails in order to end up with 12 volts or so for the motor, after passing through the DCC circuitry. I think that is the real reason that is behind the maximum voltage ratings that they use for their circuitry. Other factors come into play with AC, too, like max voltage vs. RMS voltage.

Rich K.