DCC locos on DC

[21C123]

Hi all

 

I have recently bought one of the Hornby DCC fitted SDJR Jinty unboxed from Hattons.

 

I use home made DC controllers, the circuit from Roger Amos' books.

 

When I run the loco forwards it goes well, when I stop it, switch to reverse and try to frive away it judders forwards and then stops. Sometimes with encouragement it will move in reverse but not for long, usually it won't move, just the judder.

 

I have emailed Hornby with no reply yet but wondered what is happening.

 

I will take the loco to a friend who runs Digitrax and see how it goes on DCC but I suspect my solution will be to remove the decoder.

 

Is this a common problem with DCC on DC ? If so it will only become more common I suspect, looks like chip removal will be the order of the day.....

 

 

Thanks

 

Roger

[Oakydoke]

There are a number of potential causes for poor running of decoder fitted locos on DC, but in this case the first place to look is probably the Hornby decoder.

The Jinty is very likely to have the first Hornby decoder fitted (model no. R8215). This decoder had all sorts of problems and after Hornby updated it twice in very short succession, they finally replaced it with the current model. Quite frankly, all 3 versions of the R8215 were, C**p.

As it's 99% certain that this is the decoder fitted, it might be easier just to remove it.

 

Other reasons for poor running include decoders not being set to, or able to handle DC; DC controllers with feedback or other DC trick modes; and certain cheap decoders just not being very good on DC power.

[GoingUnderground]

I believe that all Hornby decoders come ready configured to run on DC.

 

I have some early Hornby Decoders, the R8215 model, that I have fitted myself, one in a Hornby Pug and another in a Hornby Terrier, two Loksounds one I fitted myself in a 57xx Pannier and the other factory fitted in a Class 66, and a Bachmann starter loco bought simply for testing purposes. They all run on a 40+ year old H&M Duette and also on my nearly 50 years old Triang P5 controller. The Hornby chips, admittedly do run the wrong way round. For the DCC experts, it is not the connections as they run in the correct direction on DCC.

 

It could be the chip, or your control circuit as many DCC chips do not like feedback circuits, or the pick ups not touching the wheels properly and putting the loco into reverse throws them out of contact, or a stray wire or piece of metal that only causes a short when the loco goes in reverse.

 

Check that the pick-ups are touching the wheels properly as that can cause the symptoms you describe. Also check that there are no loose pieces of metal or stray strands of wire that might be coming into contact with the wheels when you put the loco in reverse.

 

Also if you have a Relco or similar track cleaner fitted that too can confuse decoders. So take that out of circuit and try again.

 

Once you've satisfied yourself that the pickups are OK and there's nothing shorting when the loco goes into reverse then you can do a rudimentary check by putting the loco on a spare piece of track away from the layout. Touch the terminals of a new 9V battery, like the ones in many smoke alarms, to the rails and the loco should run, very slowly, but it should run. Now turn the battery round so you have reversed the polarity and try again. If the loco runs properly in both directions then it's your controller. You can always use the battery in a smoke alarm when you've finished the test.

 

If it is your home built controller then replace that, otherwise you will have to remove the chip. If it's got a plug in chip then all you will need is a blanking plate, I think Bachmann now sell these, I don't know if Hornby yet do.

 

If the loco plays up on a DCC layout then it may be the chip. If it is the chip your alternatives are to unchip it or send it back to Hattons and ask for a replacement. Even if it is unboxed that shouldn't affect your rights as a consumer and the loco should be of merchantable quality, and a loco that only runs in one direction isn't in my view.

 

The only decoders that are known not to work on DC are the ZTC 255 and 4007 models, I speak from personal experience, I have several of each, and none of them work on the Duette and even struggle with the battery test.

 

Hope this helps and you get it sorted.

[21C123]

Thanks for the replies.

 

Funnily enough I had a new 9 volt battery on the layout to put in the smoke detector above it...

 

The chip was a double sided one with a 4 pin socket, and I do mean was.

 

The pickups are fine, the loco still misbehaved, I tried connecting the power direct to the motor terminals, it worked fine in one direction, slowly in the other then the burning smell started.....

 

I guess it is fried now, but the loco works fine once I took out the chip and connected the pickup and motor wires.

 

Thanks the the help, no great loss, I now know to be more careful around chips...

 

 

Roger

[Gordon H]

The pickups are fine, the loco still misbehaved, I tried connecting the power direct to the motor terminals, it worked fine in one direction, slowly in the other then the burning smell started.....

Do you mean you left the decoder plugged in, i.e. connected to the motor, when you applied the power direct to the motor terminals?

Damage to the decoder motor drive components is very likely to occur if another power source is applied to the outputs, whether the decoder itself is powered or not.

[GoingUnderground]

........I tried connecting the power direct to the motor terminals, it worked fine in one direction, slowly in the other then the burning smell started.....

 

I guess it is fried now, but the loco works fine once I took out the chip and connected the pickup and motor wires........

I did say put the loco on the spare piece of track and connect the battery to the rails. The idea was to run the loco from a DC power source that wasn't your home built controller to try to eliminate that as the fault, and most people do have 9v smoke alarms with spare batteries to hand. Sorry if you misunderstood what i was suggesting.

 

As Gordon H has said, connecting any power source across a decoder's output will almost certainly blow the decoder.

[cahill]

i would just take the chip out and flog it, you can claw back some money then. seems pointless having a decoder in that provides no use

[craigwelsh]

i would just take the chip out and flog it, you can claw back some money then. seems pointless having a decoder in that provides no use

Not now its melted though .

[21C123]

Yes i did leave the decoder plugged in, but when i tried it again later it still seems to work, though has the same fault as originally, the inability to go in reverse. It's all learning anyway. I've removed it and connected the pickups to the motor directly and the loco is great, it has a new to me version of the 0-6-0 chassis, all wheel pickup, no traction tyre and no sprung third axle. Works much better than my son's Thomas.

 

I guess with more locos being DCC ready I should find out a bit more about how to work around them if necesary.

 

I also have a BAchamnn DCC ready standard 4 2-6-0 which responds to the controller differently from the unfitted one I have. Not enough to make me take it out but enough to be noticeble. Then again it could just be teh difference is in the loco drive itself.

 

 

Roger

[craigwelsh]

You mean DCC Fitted not ready, ready means its got a convenient socket to put a chip in rather than having one already fitted..

 

DCC locos need a bit more power to charge the chip before the motor on DC, you could also have factory default acceleration/deceleration delays in place.

[GoingUnderground]

If your Bachmann Standard 4 is DCC Ready then it is a conventional DC loco.

 

DCC Ready means it is ready to be converted to DCC as it has a socket and blanking plug already installed. These do not affect the working of the motor in any way. Their only effect on a loco might be a reduction in its weight as the ballast weight will have been reduced in size to make space for the plug and socket, decoder and space for a speaker should you ever want to fit a sound decoder. Even this may not apply if the decoder socket is in the tender. You don't need to find a way to work round DCC Ready models as there is nothing to work round.

 

DCC Fitted means there is already a decoder fitted. My experience suggests to me that you should not need to work round most DCC fitted locos unless the problem is your home built controller.

 

DCC Sound means there is already a DCC Sound decoder and speaker fitted. Some of these are set up to give you loco sounds when running on DC. Both my Loksound fitted locos run perfectly happily on DC, with sound.

 

Most if not all DCC decoders do not like Relco or other HF track cleaners. Do not operate DCC Fitted locos on your layout if you have an HF track cleaner installed. Equally, they don't like feedback DC controllers.

[Gordon H]

Yes i did leave the decoder plugged in, but when i tried it again later it still seems to work, though has the same fault as originally, the inability to go in reverse.

Chances are your direct motor power application would have only damaged the components for one direction (in this case, reverse). If you had applied power to the motor the other way round as well, it is likely that neither direction would still work.