A funny thing happened...

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UrbanHermit
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A funny thing happened...

Postby UrbanHermit » Fri Feb 26, 2021 6:48 pm

This afternoon I left a train running around the oval while I got on with something else. When, after maybe 15 minutes, i tried to stop it it was completely unresponsive to any input from the controller but continued running at the speed I'd originally set. Switching to another loco's address and coming back to it made no difference. In the end I switched off the power at the socket. When I switched on again the loco behaved normally, but it's worrying to think that it might happen again.

The locomotive was my latest purchase, a Dapol GWR Mogul with factory-fitted decoder; the controller an NCE Powercab.

Any answers?
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Mountain
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Re: A funny thing happened...

Postby Mountain » Fri Feb 26, 2021 7:03 pm

Haha. I have had the same in the past on the odd occasion. It is not the end of the world. One solution is to switch to DC :lol: Ok. Enough of the humour. Somehow the signal is not getting through or the controller has had a kind of brain freeze. When it happened to me it was with a Lenz system. Very rare but like you did. I turned it off and back on and all was fine.
If it was just over a small area of track one would assume it was a small area where the track was tarnished enough to interupt the signal but not enough to stop the loco drawing power from the track. The decoder will carry on with its last instruction.

I have also had the odd decoder when the pickups may not always give 100% pickup from the track, stop and go and stop and go when the inertia starts again. It kind of acts similar to a motor with a weak magnet on DC so I first assumed that it was a weak magnet. The solution was to set the inertia to zero so that any slight interuptions would not be noticeable.

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Bufferstop
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Re: A funny thing happened...

Postby Bufferstop » Fri Feb 26, 2021 7:24 pm

Every item or digital electronics that I've encountered suffers this sort of hangup from time to time. Look for something that might cause spikes, wheelbacks touching opposite point blade, pickups touching metal chassis, conductive debris in frog gaps. NASA spreads millions keeping old technology in use because they know how it will go wrong and how to fix it.
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Bigmet
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Re: A funny thing happened...

Postby Bigmet » Sat Feb 27, 2021 10:29 am

Over about the first five years of my DCC experience I saw this loss of control with locos running but 'locked out' and unresponsive, yet all other locos on the layout performing normally in response to commands, even on the same section of track. Cutting track power then restoring it immediately had the loco with the problem restarting normally. With some loco and decoder combinations it was reliably repeatable, at speed step X it would go unresponsive, others, it would just happen once in a while. (Assortment of decoder and mechanism manufacturers.)

Every example of this I encountered was readily fixed, either by changing the decoder for another if the owner wanted the loco left unaltered; or my preferred solution of removal of all the suppression components. What was happening was resonance in the decoder, motor and suppression components circuit, sufficient in my opinion to 'swamp' the decoder. Sometimes the resonance was audible as a high pitched ringing, but you had to be very close to the loco to hear it.

It's over a dozen years since I last saw this happen, and I had rather supposed that improvements in design had eliminated this problem, but it seems not...

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Mountain
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Re: A funny thing happened...

Postby Mountain » Sat Feb 27, 2021 11:54 am

I had just been thinking about TV supression when I logged onto this and re-read the post. The locos surpressors tend to nullify the DCC signal and the more locos which have their surpressors left on them the less signal that can get through.

They used to make a point of telling people to remove the TV surpressors when hard wiring in decoders in the instructions with ones DCC system, but since the days of the DCC plugs and sockets, it all went quiet and someone said they had made ways to ypass the surpressors when one plugs in the new decoder.... BUT when I looked at the locos wiring for some of these locos that were made with DCC sockets, their TV supressors would still be in the same position that they always had been in.

I guess if one only has a few locos then it is not going to make much of a difference, but the more locos one has fitted with supressors, the less likely the DCC signal will get through.

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Bufferstop
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Re: A funny thing happened...

Postby Bufferstop » Sat Feb 27, 2021 3:47 pm

I've never seen TV suppressors mounted on the blanking plug, but it's the obvious place to put them. You automatically remove them when you fit a decoder.
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Roger (RJ)
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Re: A funny thing happened...

Postby Roger (RJ) » Sat Feb 27, 2021 3:56 pm

A few Hornby DCC ready locos now have suppression components on the blanking plug but not many.

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Flashbang
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Re: A funny thing happened...

Postby Flashbang » Sat Feb 27, 2021 6:51 pm

UrbanHermit wrote:This afternoon I left a train running around the oval while I got on with something else. When, after maybe 15 minutes, i tried to stop it it was completely unresponsive to any input from the controller but continued running at the speed I'd originally set. Switching to another loco's address and coming back to it made no difference. In the end I switched off the power at the socket. When I switched on again the loco behaved normally, but it's worrying to think that it might happen again.

The locomotive was my latest purchase, a Dapol GWR Mogul with factory-fitted decoder; the controller an NCE Powercab.

Any answers?

Turn off DC operating mode via CV29. Use this CV29 calculator link to see what value setting in CV29 is needed... http://www.2mm.org.uk/articles/cv29%20calculator.htm

BTW there is no DCC signal where RF suppression capacitors are located (across the motor terminals normally) Its DC and PWM then. These suppressors can cause issues with the Bemf reading in the decoder, causing poor/hesitancy running usually. If they are now being fitted onto a plug in some locos, then they will still be on the motor feed pair of wires connection, not the incoming DCC side. :D
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Paul-H
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Re: A funny thing happened...

Postby Paul-H » Sat Feb 27, 2021 7:45 pm

Yep I bet run on DC is enabled and a power glitch switched the decoder to DC mode, so it just ran on the converted DCC voltage as DC.

I always switch run on DC off, it can create more problems than it solves.

Paul

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Peterm
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Re: A funny thing happened...

Postby Peterm » Sat Feb 27, 2021 11:36 pm

I thirded that. :)
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RAF96
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Re: A funny thing happened...

Postby RAF96 » Sun Feb 28, 2021 9:38 pm

Diodes for directional lighting on the blanking plug, but supression capacitor is on the socket plate.
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