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Great Trains F-7A


Jerry B44
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I got this F-7 shell from a forum member, and I made B units sides/ends from a mold. I used some NWSL power trucks for the A unit, B will be un-powered, which could be a mistake. It will be battery powered. I had some Great Trains parts to finish off the trucks/grills/etc.  I will get the decals on soon. I sure work slow anymore.

F-7APaint.JPG

I used Tru-Color UP yellow, which is a good match for MTH's UP yellow.

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 I had hoped to see you also be a builder of the E series. This F looks mighty fine to me.

I was actually shocked when I looked at the NWSL truck block prices. The two axle trucks seem reasonable. The three axle trucks are much, much higher? I would be OK if they chose to maybe leave an axle unpowered to reduce costs. MTH does that. I need to go back and look at the posts for the insides of the three axle on how they're constructed. I have abandoned the E series for now with all the new engines I got and have built.

 Maybe down the road I'd consider using the MTH trucks to make the build more reasonable. I'd like to get a set of NWSL two axle trucks and compare them. I read good things here about them. Please post results of how this engine performs for you, in the long term.

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Looks really good. I love the truecolor U.P. yellow, It looks to be right on. Keep up the good work and remember, it doesn't matter how long it takes, or how fast you work on it. The only thing that does matter is you're having fun doing it. Any thoughts on a sound system for it? Larry

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Joe,

  I don't have any E series by Great Trains. Have a few parts, but that is it.  I do have some unpowered  3 axle NWSL blocks, but no motors and they are quite pricey.

 

Thanks Larry, and thanks for your help. I'm cheap on sound, or don't use it at all, probably MyLocoSound, I have a diesel by them.

 

jerry

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  • 4 weeks later...

I finished the F7A unit. It has the My Loco Sound and speaker in it. The B unit has the Rail Boss 4 and battery. Roof is removable to get to that. B unit still needs couplers.  Stan did the UP flag decal, mine did not work out. I did the rest of the decals in UP lettering on a color laser printer a friend has. Dark colors work okay on a light background.

F7AangDone.JPG

F7Adone.JPG

B unit still needs the couplers. I used red vinyl tape for the stripes.

F7ABdone.JPG

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  • 3 months later...
 
 
  • 8 months later...

The new Garden Railways Magazine (April 1016) features a favorable review by Kevin Strong of the recently available MTH F-7 AA unit with Protosound 3.0 and DCC compatibility.

 

Article for subscribers at:    http://grw.trains.com/news/product-reviews/2016/02/mth-f7-locomotive

 

Unlike most of us on this forum, Mr. Strong does not use a MTH DCS controller.  Instead, he tested it using a DCC controller (an MCR Prodiigy Advance2). And, of particular interest to me,  he also tested it with traditional analog DC using an Aristocraft (Crest) Train Engineer controller with Pulse Width Modulation (PWM), not Linear.

 

He loved how it worked using his MCR DCC controller saying that he could activate many important functions that we can do on our MTH DCS controllers. 

 

But he said problems occured from the Train Engineer's Pulse Width Mopdulation (PWM) when he tried using analog DC.  With PWM, his F-7 responded in erratic and strange ways. Like Mr. Strong, I also have observed this using Railboss 4 which also has PWM.  Not only did my MTH locos act in strange ways, Ray and I believed that PWM current also caused a 50 v capacitor to blow up in my TIU unit a few weeks ago. There was a big explosion- like a firecracker!   Thank goodness Ray was able to fix it.  Reading Mr.  Strong's similar experience, I now feel almost certain that PWM current negatively affects both the Protosound board in the locos and can actually damage the TIU.

 

Moral of the story: Don't use an MTH engine or power a TIU unit with PWM power!

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Just as a note of clarification, I cant say with certainty what caused that to happen with John's TIU (it is for sure the first time I've seen that happen) but given it was being tested with a PWM power at the time it seemed like at least somehow it could have been a possibility.  

 

I agree just stick with the advice that MTH provides in the Owners Manuals they provide with their engines to not use PWM power supplies.  

 

And as Joe said, I have tried out a number of different power supplies and have found Bridgewerks power supplies to be the best.

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Yes, of course, Bridgewerks works great since it is linear, filtered and regulated.   But I think it is important to get the word out about the problems of using PWM power since there are huge numbers of railroaders who use these popular relatively inexpensive PWM controllers, and they may purchase an MTH engine for their traditional analog DC, unaware that their controllers are harmful.  Since I too was unaware of this problem, my TIU blew up and I could have damaged my Triplex soundboard. To solve my problem I either had to buy an expensive new Bridgewerks controller and Bridgewerks remote, or try something else.

 

The inexpensive solution I came up with was to separate my PWM controller from my TIU using a DPDT switch, powering both of them with the same linear regulated power source. This way I have a choice of controllers.  For my non-MTH locos I use my Railboss4 (PWM) controller; but when I run my MTH locos, I flip the switch and use the TIU.

 

problem solved...

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On 3/1/2016 at 2:47 PM, John Carmichael said:

Yes, of course, Bridgewerks works great since it is linear, filtered and regulated.   But I think it is important to get the word out about the problems of using PWM power since there are huge numbers of railroaders who use these popular relatively inexpensive PWM controllers, and they may purchase an MTH engine for their traditional analog DC, unaware that their controllers are harmful.  Since I too was unaware of this problem, my TIU blew up and I could have damaged my Triplex soundboard. To solve my problem I either had to buy an expensive new Bridgewerks controller and Bridgewerks remote, or try something else.

 

The inexpensive solution I came up with was to separate my PWM controller from my TIU using a DPDT switch, powering both of them with the same linear regulated power source. This way I have a choice of controllers.  For my non-MTH locos I use my Railboss4 (PWM) controller; but when I run my MTH locos, I flip the switch and use the TIU.

 

problem solved...

 

I agree wholeheartedly that it is good to take the time to share what power supplies we should use and which to avoid.  The question is in your case with the TIU was that actually the cause and should we be raising this to the level of making people fearful.  From a technical perspective there wasn't anything that should have caused that capacitor to blow, it was a non-polarity sensitive (reverse voltage on a polarity sensitive capacitor will make them explode) and was rated at 50v.  From the circuit analysis there was nothing that would have induced a power variation that should have caused it to fail like that.  TIUs have voltage spike protection components built-in to protect the trains from potentially damaging high voltage spikes and those voltage protection components weren't triggered/tripped.  (The voltage spike protection is to protect the engine electronics from really old O gauge power supplies that might not have the more modern electronics to limit the spikes they produce particularly in times of heavy track shorts.)   (I should note that PWM essentially uses periods of voltage on with periods of no voltage.  Depending on the device generating the output power it can generate say 24v on for a short period then have no voltage for a longer period to get an average output of say 5v if that is what the target output is.  The voltage on output can be higher or lower it just depends and in this case I would need to connect that power supply to my oscilloscope to know.)  I'm then left with the question, is the Railboss putting out voltage output (when voltage was on) that would exceed the rating of a 50v capacitor?  It just seems unlikely for two reasons one is the capacitor should be 'seeing' the same mean effective output voltage and also two that I would think it would stand to damage a fairly wide range of other train electronics and just don't think that is likely at all.  With regards to MTH Protosound boards, TIUs and high voltage I know one individual that was running his G scale Protosound equipped engines with an old unregulated linear power supply (not PWM) that messaged me about how the sound from the engine had a lot of static.  Stepping through the troubleshooting steps I found his power supply was pumping out 36v DC to the track.  When we switched him over to a proper power supply the sound problem went away.  That engine and TIU had been run for an extended period of time on voltage way exceeding the documented recommended maximum of 24v and the system managed fine without damage.  (Do note that even if you don't outright kill a particular component running at higher voltages, it does strain components more and can lead to premature failure)

 

I think that the fact the F-7 review showed the engine didn't respond well to the PWM power supply, that a firm conclusion is being drawn that it is hazardous to use with the TIU and engines.  Again, I don't feel we have enough information to know this for sure.  Problems with PWM and train electronics is not something that is new, LGB MTS decoders and LGB sound cards along with some Phoenix sound cards have been reported to have problems with PWM.  (some say Phoenix works fine with PWM, others have noted problems with some cards)  This post here points to potential problems with DCC decoders in general with PWM DC power:  http://forums.mylargescale.com/802050-post12.html   So when you dive into it you find PWM can be an issue across the entire range of train electronics (not just isolated to MTH), but one thing that I have found notably missing from all of the discussions on this are hard warnings of certain damage.  

 

With all this background I had to make a recommendation on should the use of PWM power be discontinued or not.  Despite everything that I know from this situation and others it's why I felt it's best to error on the side of caution and follow MTH's recommendation to not use PWM.   If there was a high probability of electronics damage then I would expect to see a more forceful warning in the manuals.  So what happened with that capacitor, was it just defective or did the Railboss PWM cause it to blow... As I noted I could find no reason outside of it simply being defective, but the fact you were trying to test it out with your Railboss makes you take notice.  I just at this point think users should follow MTH advice but to not be fearful.  That capacitor was the only failed component and the TIU works fine after having it replaced. 

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One of the things I like about Ray Manley is his curiosity, analytical mind, and perseverance of the truth when it comes to solving problems.  I must apologize if I jumped too quickly to the conclusion that PWM power caused my TIU capacitor to explode.  As Ray pointed out, it could have been a defective capacitor or something else.  We just don't have conclusive evidence. So I think we should follow his advice to follow MTH's advice (to not use PWM) but to not be fearful.  But we still need to be cautious!

 

Thank you Ray for your detailed and thoughtful analysis.

 

As far as Kevin Strong's observation that Crest Train Engineer with PWC (same as PWM) caused erratic behavior from the loco's Protosound board, and his solution of using a PWC filter, I found out that Crest also sells as an accessory a PWC filter for 29 dollars. Obviously, Crest has seen problems from their PWC output and offers this accessory as a solution.  Although Mr. Strong does not say, I bet this is the PWC filter he used:

 

See: CRE57091 PWC-LINEAR BOARD MANUAL (PDF)

 

But I'd be hesitant to use the Crest PWC filter with other brands of PWC controllers such as Railboss 4 since my electronic knowledge is limited in things like this.  For the time being, I will continue using my DPDT switch solution which is working well.

 

One more comment on the two solutions (mine and Mr. Strong's).  With my solution of separating the TIU from the PWM controller using a DPDT switch, I can't run an MTH loco using DCS at the same time as a non-MTH loco since I'd have no throttle control over the non-MTH one.  But using Strong's PWM filter solution will allow him to run two locos at the same time and still have throttle control over the non-MTH loco.  Of course, he would not be able to run the non-MTH loco in reverse while running the MTH loco simultaneously because the reversed polarity of the Train Engineer would prevent the TIU from functioning.

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  • 9 months later...

I agree fully in regards to Ray's in depth analysis and in particular of his taking the time to make correct ananlysis. It has saved many of my engines from destruction and has helped me make my DCS operation viable over here in a country where there is no DCS service at all whatsoever.

 One question comes to my mind though and it is this: Can one use say the newer generation Aristocraft train engeneer with the switch set to linear power fed by a Bridgewerks power supply to run MTH DCS engines in analogue mode without harming them?  This is interesting to me because I am an older generation and am used to analogue, and also because I have a lot of European equipment which runs on analogue and this would save me the hastle of switching from DCS to analogue every time I want to use one or the other. Yet I enjoy DCS scope to operation (maily the possibility of switching cars onto a train stopped on the main with a switcher or changing engines without needing any cab control, which is unpractical outdoors) and wish to keep the option to operate on DCS when I want to.

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On the Train Engineer I would think yes you can with no problems.  Someday if I ever get an Aristo Train engineer I'll hook the output up to my Oscilloscope and check out the DC sine wave over a varying range of voltages to see what it looks like.

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  • 1 month later...

Thanks for that info Raymond, as it would solve a lot of problems that I have.

 One of these is as John Carmichael noted, the problem of operating MTH DCS locos with other locos which are not DCS. This problem is becoming very real for me as I have redetailed a Lionel GP7 which now runs fine with North West Short Line wheelsets and is analog, and I would love to latch it up with my F3 A-B-A which is MTH DCS, so that would make a spectacular MU lash up.

 

By the way Jerry congratulations on that F7 it is very nice.

 If anybody hears about one of those Great trains E units I would be very interested in finding one or two, and I have absolutely no chance of finding one here in France, So if you could let me know about it I would apreciate it. It was the mainstay on the PRR. But thank god I am modeling the PRR in the steam era and can use the PA1 meanwhile.

P1050338.JPG

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