Railpower 1300 testing

[metalworkertom]

Tech II 1500
Specs 20VDC variable 17VAC  22VDC fixed
Meter readings at 100% 21.32 VDC variable 18.86 ACV 23.9 DCV fixed
Again at 25% 50% 75 % 100% Sorrre.y the photos are out of order he

[mmagliaro]

While those two have higher peaks than some of the others, they are still around 23, not 25.   Is the 9500 or 1500 even still made?  I don't think so.

I am of the opinion at this point that these packs are flirting with the hairy edge of what a DCC decoder is supposed to tolerate according to the NMRA spec, which says that "in no case should the peak amplitude of the command control signal exceed 22 volts."   And the spec days that decoders have to withstand a DC voltage of at least 24 as measured at the track, so that would not be peak, but average.  While none of these packs are exceeding 24v avg, they ARE exceeding the command signal peak limit with pulses.   It seems like a really bad idea to be powering the track with voltages so close to the allowed decoder limits, especially when there is absolutely no reason to have to put voltages like that on the rails to operate a DC locomotive.

[Point353]

While those two have higher peaks than some of the others, they are still around 23, not 25. 

I am of the opinion at this point that these packs are flirting with the hairy edge of what a DCC decoder is supposed to tolerate according to the NMRA spec, which says that "in no case should the peak amplitude of the command control signal exceed 22 volts."   And the spec days that decoders have to withstand a DC voltage of at least 24 as measured at the track, so that would not be peak, but average.  While none of these packs are exceeding 24v avg, they ARE exceeding the command signal peak limit with pulses.   It seems like a really bad idea to be powering the track with voltages so close to the allowed decoder limits, especially when there is absolutely no reason to have to put voltages like that on the rails to operate a DC locomotive.

To what value does the output voltage drop if you apply the maximum load of nearly half an amp?

[mmagliaro]

At 1/4 amp, full DC is 13.6v average, and the peaks are at 23 volts.

But really, I think this is thinking about it the wrong way.  We already know that with ordinary motor loads on this thing, it doesn't cause any damage.  The question is, could it damage decoders?   Therefore, whether the voltage drops to a safe level when there is "enough load on it" is not relevant.  When a decoder is across the power pack, it could easily see 25 volt peaks when the motor is not on.

(And frankly, even 23 volts is pretty darn high).

[Doug G.]

Of course, these packs were designed to bump or vibrate regular DC motors into action. Thus, the pulses up into the 20-some volts range without motor damage. The pulses diminish as the throttle is advanced.

Of course, many newer motors don't need pulse power (due to closer tolerances, skewed armatures, etc.) but many of them from when these packs were designed (in the nineteen eighties), did/do.

I guess it behooves the DCC enthusiast to determine whether or not damage will be done to their decoders from a given power pack or make sure the power supply is designed for DCC.

I realize this post is not really related to the subject but I just think it's appropriate to keep things in perspective. And thank you guys for the waveform pictures. It's interesting to see them from the packs I own.

Doug

[Point353]

At 1/4 amp, full DC is 13.6v average, and the peaks are at 23 volts.

But really, I think this is thinking about it the wrong way.  We already know that with ordinary motor loads on this thing, it doesn't cause any damage.  The question is, could it damage decoders?   Therefore, whether the voltage drops to a safe level when there is "enough load on it" is not relevant.  When a decoder is across the power pack, it could easily see 25 volt peaks when the motor is not on.

The NMRA spec for the output of a DC power pack is that it "shall not be less than 12 volts direct current at maximum anticipated
load." 
Does the output of the 1300 meet that spec at its rated maximum 7VA load?

Also, is the output of the 1300 no greater than 24VDC when loaded by a dual-mode decoder equipped loco just sitting on the track (but not running)?

[Maletrain]

Does the output of the 1300 meet that spec at its rated maximum 7VA load?

Also, is the output of the 1300 no greater than 24VDC when loaded by a dual-mode decoder equipped loco just sitting on the track (but not running)?

I think the subject of this thread is whether there is any measured data that indicates why Rapido is seeing damage to their decoders from the 1300s, but not other power packs.  And, I think that the data shows that the 1300 had higher voltage peaks than the other packs, slightly exceeding rather than just barely meeting the electronics' voltage specs. 

If somebody really wants to know how Rapido decoders will handle the 1300 voltage environment, they need to buy some Rapido decoders and put them on a 1300 and see what happens on a scope.  Which is probably just going to verify the experience that led Rapido to put out their warning about the 1300.  Finding out exactly why, when and how a 1300 blows a Rapido decoder seems like a waste of time and good decoders.

To me, the issue is settled: Don't run any DCC/DC decoder on a DC power pack without getting the power pack scoped, because just reading the specs and compliance with NMRA standards is not telling me that it won't damage the decoder.  Assessing "blame" on the manufacturer of the decoder or power pack is not going to help me when I have an loco with a blown decoder.

For the future, it seems like manufacturers of decoders have to either warn people away from power packs that damage their decoders, or make decoders that can handle something like 35 volts to gain back the intended margin against pulses.  But, if decoders are designed to withstand higher voltage, I expect they will be larger - do we want that? 

I still think that the best solution is to have locos come with DC circuits that allow plug-in of DCC decoders and plug-in of speakers if DCC sound decoders are selected.  That way, the "dual mode" decoders aren't needed.  And, folks who want to run DC can do that without having to pay for a decoder they aren't really using.  Of course, people who want sound and DC are going to have to do the research to make sure their sound decoding electronics can withstand their power packs.  But, at least that is their choice to try to straddle the two worlds - it is not being forced on them by the manufacturers.

[nkalanaga]

Or, since DCC seems to be the future, use plugs and include, or offer, a standard DC jumper plug, so us old-timers can REMOVE the decoder without damaging it, or the loco, or possibly ourselves.  Yes, we'd have to pay for a DCC model when we don't need it, but that's the way it's always been for minority modelers.

Again, no need for dual-mode decoders, and the future majority get what they want.

[Point353]

I think the subject of this thread is whether there is any measured data that indicates why Rapido is seeing damage to their decoders from the 1300s, but not other power packs.  And, I think that the data shows that the 1300 had higher voltage peaks than the other packs, slightly exceeding rather than just barely meeting the electronics' voltage specs. 

If somebody really wants to know how Rapido decoders will handle the 1300 voltage environment, they need to buy some Rapido decoders and put them on a 1300 and see what happens on a scope.  Which is probably just going to verify the experience that led Rapido to put out their warning about the 1300.  Finding out exactly why, when and how a 1300 blows a Rapido decoder seems like a waste of time and good decoders.

Jason from Rapido now needs to determine (and report here) whether or not the dual-mode decoders used in his company's N scale models can survive without damage the continuous application of 24VDC (or 27VDC for HO scale models) per the NMRA spec.

[Maletrain]

Jason from Rapido now needs to determine (and report here) whether or not the dual-mode decoders used in his company's N scale models can survive without damage the continuous application of 24VDC (or 27VDC for HO scale models) per the NMRA spec.

Not clear why you think Jason needs to do anything.  But, if he does something, it seems to me that showing his decoders die at 25 v pulsed power is sufficient to make his point (That is different from steady DC).  And, we have only seen one 1300 on a scope.  How do we know that others don't go to lower and higher peaks, due to some manufacturing variability.

For purposes of TRW postings, I think our tech-savvy posters have done a great job of teaching us that the published specs on DC throttles do not tell us what we need to know about their compatibility with DCC decoders or other electronics we may choose to hook to them.  I remember the thread on caps, where the recommendation was to allow plenty of margin between the actual applied volts and the spec on voltage limitations. 

[Point353]

Not clear why you think Jason needs to do anything.

Because he is the one asserting that "the RailPower 1300 is notorious for voltage spikes and it WILL destroy your locomotive."
https://rapidotrains.com/ho-scale-absolute-rdc-support/

An HO decoder is supposed to be able to withstand the application of up to 27VDC.
The tests results on the 1300 here show no output higher than 25VDC.

Furthermore, the 'scope photos presented here show no evidence of any "spikes" that would meet the definition as given by peteski.
Maybe Jason should be posting 'scope photos of his own to illustrate whatever "spikes" he is alleging that the 1300 power pack might generate.

[metalworkertom]

I have a second 1300 that measured 5.47 v max at 25%. 15.88 v max at 50%. 20.86 v max at 75%. And 24.69 v max at 100%. Secondary ac voltage measured 19.78 v no load with meter.

[mmagliaro]

Because he is the one asserting that "the RailPower 1300 is notorious for voltage spikes and it WILL destroy your locomotive."
https://rapidotrains.com/ho-scale-absolute-rdc-support/

An HO decoder is supposed to be able to withstand the application of up to 27VDC.
The tests results on the 1300 here show no output higher than 25VDC.

Furthermore, the 'scope photos presented here show no evidence of any "spikes" that would meet the definition as given by peteski.
Maybe Jason should be posting 'scope photos of his own to illustrate whatever "spikes" he is alleging that the 1300 power pack might generate.

The DCC spec also says that at no time should the DCC command pulses exceed 22 volts.    Although these sine wave pulses don't look anything like a DCC command, who's to say that they still cannot damage a decoder?

[mmagliaro]

And here's the 1300 schematic everyone's been waiting for.
I did this in a circuit simulator, so I could also "run" it and confirm that I had the schematic right.  Indeed, I get the
same pulse pattern that the real thing does.  The absolute peak in the simulator is not up to 25.  It is at about 23.5.
But that can easily be caused by the transformer or the Darlington not being simulated exactly the same as physical ones that are in the unit.    The transformer is modeled as 27v peak to peak, which is about what the MRC pack does.

Note:  The 4 diodes ARE in fact wired up as a full-wave bridge.  The funky half-pulses are created by that 10k resistor that they tapped off the AC input from the transformer.

[Maletrain]

Point 353, we are just going to have to leave it that we disagree, because I am not going to argue.

And, TRW is not a court of law.  So, Jason does not need to prove anything beyond reasonable doubt here.

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.