# Locksound back emf



## Enginear (Jul 29, 2008)

I installed a ESU Locksound 3.5xl sound decoder into my sd40-2 USA trains engine. I have placed it since on a shelf for poor operation. It pulses bad and runs poorly. I was thinking the back emf settings needed adjusting, but I never did try. I got confused with the accompanied directions. Should I defeat the back emf or change? 
Does anyone use these decoders? They sound good. The engine also stalls on areas of track that may have had poor power. I tried rewiring but I've since switched to MTH DCS control. Any advice on settings? Joe


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## steam5 (Jun 22, 2008)

I do not have experience with this decoder, but back EMF on Lenz units. 

Is it at all possible to turn the BEMF off? If so try it, does the loco performance improve? 

Also is it possible the motor is pulling more current then the decoder can handle? 

Just a couple of quick thoughts


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## Torby (Jan 2, 2008)

I'm not at all familiar with that unit, but I do know a little about "control systems." 

By pulsing, you mean it surges forward, then slows down, then surges forward again? 

There are 2 parameters in a control system, "gain" and "damping." This happens when the gain is too high, or the damping is too low. If you adjust your gain too low, the engine will slow down a bit as the load increases. If you set your damping too high, the loco will respond slowly to changes in grade and such, either slowing down then catching up, or speeding up before backing off the power. The behavior you see is called "hunting," as the control system tries to find the right power setting. Think of a teenager first learning to drive, too much gas--hit the brake--too much gas--hit the brake. My car does this badly if I try to set the cruise at 50. 

If you turn your gain way up, you can get "oscillation" which can be pretty exciting.


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## Enginear (Jul 29, 2008)

There is cv's similar in the back emf that do as you just described, and I thought that was the problem. Now that I think of it my HO prodigy system was sitting around so I used that instead of the digitrax superchief with a switch for scales (voltages). When I test the engine on regular dc transformer it still pulses badly. Joe


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## Greg Elmassian (Jan 3, 2008)

Turn off the BEMF first and see how it runs.... a poorly running loco will not dramatically improve under BEMF... 

If it runs fine with BEMF off, then, unfortunately, you may have to set the BEMF parameters, there are 3 of them, but not all decoders allow you to change all 3. You will have to read up on it to see how to set them, there's no standard... 

Regards, Greg


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## Peter Osborne (Jan 5, 2008)

The Loksound XL is rated at 3 Amp which would not give you much headroom on a USA trains diesel. They are famous for being Amp hogs. Are you sure it's not the overload that is tripping and then resetting? Does it run any better on straight DC? 

Peter.


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## Greg Elmassian (Jan 3, 2008)

Joe, did you try turning off the BEMF yet? Your symptoms really sound like BEMF problems. I've experienced this on other locos. 

Let us know how the operation is affected by this. 

Regards, Greg


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## Enginear (Jul 29, 2008)

Posted By Peter Osborne on 09/28/2008 7:51 AM
The Loksound XL is rated at 3 Amp which would not give you much headroom on a USA trains diesel. They are famous for being Amp hogs. Are you sure it's not the overload that is tripping and then resetting? Does it run any better on straight DC? 

Peter.
Hey Guys, thanks for the help. It's been so long I forgot to check for replies, and I didn't tag them. I also have an issue that when ever I log on to this site my spyware detects a bad tracer.
Anyway the engine runs great without decoder. It also ran great with an NCE 4 amp. On the Locksound it does the same pulsing with regular DC. I have not messed with the engine since because I switched my layout to DCS. I don't have meters but when I connected a 12v auto charger to the track the engine drew about 2.5 to 3 amps. It did draw more than my old transformer could put out and forget the smoke unit. Now I switched to ac current with the dcs. I can't decide wether to keep it and have Ray add DCS, or get it right with locksound and sell it, or strip it apart and sell it (DCS won't control the locksound). I'll have to pull it out of the box and try connecting it to dcc, and then switch off the back emf, Joe


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