Question for n scale MRC Tech 7 Ampac 760 users (in DC)

[fanofallcanadianrail]

Are there any n-scale DC operators that currently own/operate the MRC Tech-7 Ampac 760 power pack ?

I ask because 2 local-area train shops carry that particular pack, yet the power output stated on it is 23V DC, and I have

been told that can damage N scale locos in DC.  Who owns this pack, and is this the case ? The box the pack comes in says :"suitable for HO/N/Z scales", but I am concerned with this seemingly high voltage output. Maybe I am worrying for nothing, but what better way to find out than to "put it out there" ?   This is NOT some obscure pack. It is the only one made by MRC that has the momentum feature, which I desire. The "700" model is rated a more modest 15 V DC but does NOT have the momentum feature I want. Please no "why aren't you running DCC ?" . Its DC I am operating, and just wanna be sure this particular pack wont fry my Kato & Atlas locos. Thanx very much....from those that have "been there" !    And btw, MRC does not answer my simple question...I have tried, twice.

[glenng6]

When I contacted MRC, regarding the purchase of my Tech-7, their response was quick and quite helpful. Unfortunately, I run HO. Hopefully, someone will be able to help you. I would give them a little extra time because of the pandemic and all. You will not be disappointed with that controller. Glenn

[cid]

Sorry to be so late to the party, but... There are still a boatload of pre-owned MRC powerpacks available with momentum.

[douggosha]

OK, I am really late but I think I answered in another forum. I have a 760 and there's no problem. By the time you turn the throttle up to where it's outputting 23 volts, your train will be off the track on curves or, at least, going faster than you really want it to go.

I am impressed with this pack's ability to keep a locomotive at a fairly constant speed going up and down grades.

Doug

[douggosha]

OK, I want to add a little more about power packs. Many people make statements about them without understanding how they work or how electricity works. Now, I am NOT talking about the OP here. I am talking about who ever gave him the "warning"

A typical DC power pack's ratings are derived from maximum output measurements. The pack is NOT always going to be outputting that voltage. That is the maximum voltage output at zero load. I realize people may not be trying to say a given pack always puts out that maximum but that's the way it comes across.

Anyway, the pack throttle determines the voltage output at any given time on the track. As I said above, if you typically turn a power pack to its full output, your locomotive will be off the track or going too fast and it will be long before you reach that level. Within the normal speed ranges, there is absolutely no problem with voltage level.

Potential current capability of a power pack is of more concern because if you have a pack with a high current reserve, you can have a problem if you accidentally have a short circuit by, say, a derailment and wheels shorting out opposite polarity elements in a switch, say.

Of course, a power pack does not force a locomotive or anything else to accept current but it can supply that current, if necessary. If wheels are short circuiting on the track, that full current will flow through the wheels and axles and heat them up, sometimes with disastrous results, melting adjoining plastic structures like trucks, etc.

That isn't really a negative about high power packs. DCC guys live with that possibility even more so because they have full voltage and current on the tracks at all times. We DC guys only have to worry about it at relatively high speeds (hopefully, nobody runs their trains that way, anyway) and with packs capable of supplying, say, 2 amps or more.

The thing to remember is, if your train stops or slows down, turn the throttle OFF, not UP to try to get it to run faster, until you investigate whether the problem is due to an open circuit or short circuit.

Doug

[benevideslauren]

Of course, a power pack does not force a locomotive or anything else to accept current but it can supply that current, if necessary. If wheels are short circuiting on the track, that full current will flow through the wheels and axles and heat them up, sometimes with disastrous results, melting adjoining plastic structures like trucks, etc.

[douggosha]

While I'm here, today, when I said a train will be off the track at full throttle, I was thinking more of older locomotives which tun faster. Modern locos typically don't run as fast and may not leave the track but we normally wouldn't run them at full throttle anyway.

Also, it isn't voltage, alone, that heats up a motor, it's voltage AND current.

Doug

[ncrc5315]

Voltage won't heat up a motor, current heats up the motor. Now granted, there has to be voltage to push the current, but there can be full voltage, as long as there is no current flow, there is no heat. Myself personally I would have some type of mechanical stop on the throttle, to limit the top end of the voltage output.