# power pack upgrade



## airshot

Looking to up grade my power packs for my N scale train. As I am just getting started again all I have is just the little cheapie packs that come with starter sets. From my reading 
MRC appears to make a good power pack without breaking the bank. In my searches I have
read a lot about the pulse control giving the train much better low speed control so I want this feature. I have found a model 700 twin cab power pack with pulse on each cab control.
Total of 4 amps power, can anyone tell me if this would be a good upgrade or would I be better with another? Also looking at a Tech II model 2400 single cab, better or worse?
Was also recommended to me to stay away from momentum control for N scale trains, yes/no? Most of my locomotives are Bachman and Athern, nothing expensive or high tech.
Any information to help me along will be greatly appreciated, Thanks in advance.......

Airshot


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## Howard1975

Hello, I posted the following reply to your other similar question, at this forum. Now after reading this post also, I did not realize you might have some newer locomotives (such as N scale Athearn and Bachmann). I personally would get one of the MRC Tech II power packs, or something newer like the Tech 4 version. 

The MRC model 700 twin cab power pack is fine for the older locomotives with the open frame motors, but won't be as good with the modern can-motored locomotives. 

If only you can find one extremely cheap, and it's in great condition, it could be a good bargain (for old style motors). But please check it for safety. They are quite old, and because it's case is metal, you don't want to get electrocuted, if the insulation inside is going bad. The newer power packs are all plastic cases, which is safer. If you decide to purchase an older pack, please check the case - it could corrode or rust over time. Also check the power cord to make sure it's still in good condition. And also make sure the circuit breaker is working good enough to protect your equipment, in case of derailment.


Also be aware, it was designed at a time, when locomotives were powered with open frame motors, which needed a huge amount of energy to get going. Most newer locomotives have can motors, which are much more energy efficient. If you want to run modern can motored locomotives, with a power pack designed for very old open frame motors, don't expect the smoothest starts, or good slow speed running.

You can use the pulse power on those ancient power packs, ONLY if you use old style open frame motors. DO NOT use the pulse power from an ancient power pack on a locomotive with a modern can motor. You are just asking for trouble. You would need to turn off the pulse power to run the newer locomotives.

The older power packs will not give you the best control for the new can motors. Those ancient power packs do not use transistors like the newer ones, just a simple rheostat to control speed.

Personally I would not use those ancient power packs to control today's modern locomotives, especially not N scale. It will be fine with ancient HO scale and larger locomotives, with open frame motors. And it can always be used to power accessories, such as lights around the layout, and the switch machines on turnouts.


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## ckblum

Modeltrainstuff.com has the MRC 760 on sale right now for $59.99. I just bought one myself, the first I got was a did but the replacement should be here soon! I have mostly older locos but I don't think a new power pack is gonna have any negative effects. Like Howard said, if it was the other way, newer locos and older pack I wouldn't run it.

For the price it's a decent setup with the momentum and brake control, which you can turn off if you want as well.


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## airshot

Other people have mentioned not to use the "momentum" on N scale locomotives, pulse is fine but not momentum. Not sure why, but that is what was told to me. Looking possibly at a model 2400, also looked at a model 260 but sold to quick. Any other ideas or suggestions are greatly appreciated. Thanks

Airshot


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## ckblum

You wanted to run two trains right? Have you seen the MRC 780? No momentum control on it, but it has the pulse power I'm pretty sure. I'm not sure your budget but that price is only $5 more than my 760.

http://www.modeltrainstuff.com/mobile/Product.aspx?ProductCode=MRC-1278


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## airshot

Still confused on the pulse and momentum switches. I understand what they do, but have heard many stories about whether they are needed or not. Some say the newer controls do not need pulse as it is already built in. Others say never use the momentum on N scale as it will cause them to overheat and destroy them. What are the experiences of the more educated than me group out there? I am now leaning toward a newer type of power pack, probably separate cabs, but not sure on the pulse and momentum extras when used in N scale. Once again many thanks for helping an ole timer make up his mind....

Airshot


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## Howard1975

Airshot, I agree with you, it can get confusing with all the talk of pulse and momentum. I have two MRC Tech II power packs, the 2500 model. That model has momentum, but to be honest, I don't use the momentum feature, only rarely. I used to have a very old "golden case" power pack, the MRC Throttlepack Model 501, until it stopped working a few years ago. That old power pack included a pulse power switch. I had that power pack probably 25 years before it quit. Before it went bad, it worked fine with older equipment, but sometimes my newer locomotives would get hot with the pulse power on. 

I'm no expert, but I have been playing with model trains for the past 30 years, since I was a kid. In all those years, I've had many N and HO scale locomotives from various manufacturers, of various ages. I have had no problems with my Tech II 2500 power packs with the momentum, but I only use the momentum feature rarely. Bought both of the Tech II's used, maybe 10 years ago. The MRC 2500 has a momentum switch, a brake switch and a pulse that is stronger than many other power packs. The bad news is you can not turn off the pulse on the 2500, but the good news is, it's stronger at slow speeds and then gradually lessons as speeds increase, and eventually fades out. It is some type of pulse width modulation I believe. It's much more refined then the old style pulse power available in the "golden" MRC cases. 

The problem with the old style pulse power, is some motors can get too hot, especially in N scale, and also some smaller HO. The real danger would be overheating from using the pulse power, would be an extended running period, running at low speed. At low speeds the motor inside the locomotive barely gets any cooling, and because of the way pulse power works, it can increase the overheating. 

Pulse and momentum are both extras, but not the exact same thing. Old style power packs had a simple system to pulse the power, which can be helpful to get a motor running at low speeds, but the side effect is more heat. Pulse power has no need or benefit at higher rpm's, it's only for a smoother low speed switching at low rpm levels. Momentum is a little bit different. It allows the locomotive to very slowly accelerate and decelerate, like a real locomotive does. A real loco has a huge amount of mass, it's quite slow to accelerate and decelerate. Momentum on a power pack simulates that effect with electronics. 

I'll post a few links now, if I'm allowed, that explain this hopefully better then me. Lot's to read. Hope my links work okay.

http://www.trainboard.com/grapevine/showthread.php?125077-Pulsing-vs-Non-pulsing-DC-Power-Packs&

http://www.trainboard.com/grapevine/showthread.php?121619-DC-pulse-control-can-it-damage-a-locomotive

http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=49792

http://cs.trains.com/mrr/f/88/t/206247.aspx

http://www.sumidacrossing.org/LayoutElectricity/ModelTrainPower/PowerPackTesting/


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## airshot

Great explanation Howard, thanks for the laymans deciphering for me. I am going to look for the momentum feature and forget about the pulse feature for now. Looking at a few different MRC packs and going to narrow it down here soon. Thanks

Airshot


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## airshot

*which power pack?*

OK I think I have narrowed it down to a few models and would like anyone's opinion both pro and con, on any of these. All are MRC dc power packs and all have the momentum control and all are within 10 bucks of each other.

MRC model tech 4 260

MRC model tech 7 1276

MRC model tech 4 220

The only difference I can see is the slightly less power in the 220, 260 has the most power but only slightly, and the Tech 7 (1276) is the newest model. I have a small layout so the power on any of these will be more than what I need. Any experiences with these or other recommendations will be appreciated, Thanks

Airshot


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## Howard1975

I'm glad my explanation was helpful for you Airshot. I have never tried any of the newer power packs (only my Tech II technology), so I'm can't comment on them directly. I don't have any personal experience with them. But from what I have read online, both of the tech 4 models should be okay for your needs. The tech 7 model is a brand new product, so I can only hope it's still the quality product I expect from MRC power packs. Both of the tech 4 packs have similar features, but the 260 is more powerful. Tech 4 220 w/16VA & Momentum, while the Tech 4 260 w/20VA & Momentum. The MRC model tech 7 1276 is usually called the TECH 7 AMPAC 760 and it also has 20VA & Momentum. The newest models, the tech 7 series, have upgraded electronics inside. 

Below is a portion of the instructions from MRC, for their newest Tech 7 model 760, which explains momentum quite well. 

*Momentum Switch: (Model 760 only) The momentum switch in your Tech 7
unit, allows operation in either of two modes. With the switch in the OFF posi-
tion, a change in the throttle setting results in an immediate change in loco-
motive speed. With the momentum switch in the ON position the locomotive
starts out more slowly like a real locomotive. This switch can substantially
add to your model railroading enjoyment. When a real locomotive is given an
increase in throttle setting there is a lag until the pre-set speed is reached.
The heavier the load of the cars being drawn, the longer the lag time. Similarly,
when braking a real locomotive, a considerable distance is needed in order to
stop. Since lightweight models do not mimic this delay on their own, momen-
tum circuitry, as in this pack, is used to create it electrically.*


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## ckblum

The 1276 is the pack I'm waiting on right now. I was debating between that and the 1278 (dual cab control but no brake and momentum features). I have pretty much all old equipment, old Minitrix F9's, ConCor PA1, older Life-Like. I've also been told pulse power is more critical if you run an older pack with newer equipment, the opposite scenario (older equipment, newer pack) shouldn't have any negative effects as the pulse power has been refined to run with newer equipment.

Who knows though, maybe this is all wrong and my locos will all burst into flames as soon as I try this new pack haha.


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## airshot

In my reading the mfg claims that the new tech 7 models read the power drop on your loco when grades or heavy loads or even a slow spot in the track and is supposed to make minor adjustments to the throttle automatically to compensate and keep the loco at a more constant speed. I have not heard any complaints from the new technology so I am leaning toward the tech 7 with the newest technology, also there is a company online having a sale on them for 60 bucks, same price as all the other models, so for the money I might as well get the newest unless someone jumps in that has had issues. Thanks for all the responses, this has been quite an education for an old fart.

Airshot


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## Howard1975

Those newest MRC Tech 7 packs seem to have some sort of pulse-width modulation, or something to that effect. I've also seen them compared to the Back-EMF (back electromotive force) technology many of the better DCC decoders include now. The electronics inside the tech 7 power pack senses your train is running slower (like going up a hill), so it compensates by increasing the voltage going to the train, thereby maintaining the speed you desire. The exact same thing the better DCC decoders do, when equipped with Back-EMF technology.

In the old days you needed to give your train extra power to help get it up the hill, and then let off the power some, once it has reached the climax of the hill, so it would not gain too much speed going downhill and crash. By the way, I need to do the exact same thing when I'm driving my car on hilly terrain. The cruise control does not work anymore, so I need to give it a little more gas to get up a hill, and then let off the gas some once I reach the climax, and often just coast down the hill until I reach flat terrain again. 

With Back-EMF technology you no longer need to continually adjust the speed with the throttle, because the computer is doing that for you. It's like a cruise control for model trains. That is what the latest technology in the MRC tech 7 power packs enable. 

I should mention one other thing. I have looked at the MRC web site, at each of their tech 7 models. The 760 is listed at 23v while the other 2 packs in the Tech 7 series, the 700 and the 780, are listed at 13.5v and 14.5v respectively. The 700 and 780 are more designed for N and HO scales, while the 760 can also be used with O and G scales, along with N and HO scales. Be aware that 23 volts is a lot for tiny N scale motors, so if you go that route, please be careful with how much voltage you give your trains.

By the way, my MRC tech II power packs, the 2500 model, are rated at 20 volts. So I'm careful how fast I run my trains. As long as I keep to between 0 and about 12 volts with N scale, everything will be okay. It means I can only use about half of the range on the dial, but that is okay with me, because I remember it. But when my nieces come over to play (3 and 6), I do need to keep an eye on them, so they don't burn out my trains, hehe.


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## airshot

Thanks for the information, you made it sound much easier to understand than the website. On my small layout I rarely reach more than 25% throttle probably more like 10-15% normally so the high voltage meant nothing to me other than it has a lot of reserve power so it would run a lot of locos if the need arises. It will be used on the inner loop primarily as that is where the yard work will be done. The outer loop will be using one of the cheapie starter units as the trains will just be cruising to get to their intended destination b4 switching to the inner loop to drop/pickup their next load. With the sale price all the power packs were the same price within a couple bucks of each other so I thought I would go with the most technology. Can't wait for it to arrive.

Airshot


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## Howard1975

You're welcome for the information Airshot. I'm glad it was helpful for you. If I may ask, which power pack did you order? Hopefully it will meet all your needs once it arrives. 

Howard


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## trains galore

Interesting advice about the old open frame motors, they certainly do need a bit of juice to get going I have an old Pace controller (bought it second hand from my train club, they were made over here and can't seem to buy them online, maybe they don't exist anymore)
Anyway it is a brilliant controller, runs all my trains smooth, though I was a little suprised to find it's maximum output was 17 volts I thought oo was 12v, but my old single channel does it too so maybe they did it to get the older trains to work, they certainly aren't as smooth or as efficient as can motors, also to compensate for running multiple trains at once.
My old trains work on it ok (when they work) and my new ones don't have a problem. It is interesting in that a really good quality analogue controller sets you back nearly as much as an entry level dcc but I wanted analogue to start with as programming is not my strength but I love doing basic electronics and wiring
I nearly went for a walk around set up but 100 bucks a handheld was too much when I could buy a dual controller for the same price


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## airshot

Howard1975 said:


> You're welcome for the information Airshot. I'm glad it was helpful for you. If I may ask, which power pack did you order? Hopefully it will meet all your needs once it arrives.
> 
> Howard


I went with the newest tech 7 model, more power than I will ever need but it was on sale for 60 bucks same price as the others. The reading of the loco speed and adjusting accordingly really caught my eye. With all the good reviews on MRC packs I believe this one will work.
At a much later date I will probably look for a better pack to replace the old starter pack for the outside loop but for now.......one thing at a time. Going to start the wiring (blocks) tonight and will keep me busy until the new one arrives, then it should be plug and play.

Airshot


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## Howard1975

airshot said:


> I went with the newest tech 7 model, more power than I will ever need but it was on sale for 60 bucks same price as the others. The reading of the loco speed and adjusting accordingly really caught my eye. With all the good reviews on MRC packs I believe this one will work.
> At a much later date I will probably look for a better pack to replace the old starter pack for the outside loop but for now.......one thing at a time. Going to start the wiring (blocks) tonight and will keep me busy until the new one arrives, then it should be plug and play.
> 
> Airshot



That sounds like a good price for it. Hopefully it will meet all your expectations.


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## airshot

Wow fast service, the power pack arrived today, started the wiring but not going well, posted that misery in the tech section. Did a quick wire job just to test the new power supply and yes it Works fine. Now on to the headache of figuring out the wiring mess.


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## Howard1975

airshot said:


> Wow fast service, the power pack arrived today, started the wiring but not going well, posted that misery in the tech section. Did a quick wire job just to test the new power supply and yes it Works fine. Now on to the headache of figuring out the wiring mess.


That is sure quick service, wow. Good to hear the power pack arrived so quickly, and is working fine. Now to get your wiring sorted.


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