Dcc problem.

[Geordie088]

Afternoon all, hope you are staying well. I have a question regarding my new Gaugemaster prodigy express controller and my new Bachman class 121 bubble car.

I have been getting to grips with my new controller and generally very impressed. However, I recently bought a bubble car and I was testing it yesterday. It was working well, until I had a bit of debris left on the line and the train collided with it. Not a big crash with no external damage. I had tried to use the emergency stop button but was too late. I dusted the unit off and got set to re start it, but it is totally dead.

When I try to select it and move the unit, it moves a few millimetres and stops. No lights are working on it either, which were working before hand. I have tried to set up the unit again, even trying a new address but it is the same every time.

All other locos are working as normal.
Any thoughts on what I can look at to get it moving again??

Cheers

[Bufferstop]

How severe was the collision? If it just ran into some rubbish the most likely damage would be to the pickup wipers, if they got tangled they may not be making contact any longer. If it was quite a violent collision or the loco was thrown off the track something may have moved inside pulling a connection apart, you won't know without looking inside.

[Geordie088]

It was a very minor or collision. No derailment or obvious damage. It just ran into a stray piece of track. It was very gentle.

[Bigmet]

Perform a decoder reset, then try setting the address you want. (Sometimes it take more than one reset.)

Explanation:
Probably a short occurred somewhere in the unit as it had its crash.
There must still be power reaching the decoder as you report it moves 'a few millimetres', but it is not accepting commands properly.
Most likely the working copy of the decoder firmware has been corrupted.
Reinstating the firmware by means of the reset should fix this.

[Geordie088]

Thanks as always for your help.

I have tried resetting based on some advice I found on the interweb! It suggests resetting a cv value on the loco and resetting the address. This hasnt worked however. Am I trying the correct procedure or am I doing something wrong?

Cheers guys.

[Bigmet]

Don't know yet!

Do you have the poop sheet that came with the decoder installed in your 121? That should tell you how to reset: select CV8 - that's standard for all DCC decoders - and then enter a value, common choices are 8 or 33, but it could be anything, whatever the decoder manufacturer specifies.

Now, experience. It often takes more than one go for a decoder to reset. If the reset doesn't 'take', try again. And repeat with some time between attempts. One decoder took a month before it finally responded, still working normally many years later. (Quite why this is I don't know, but a German retailer gave me this advice early in my DCC journey, and it has been invaluable.)

Something to check however: if you can see or smell that a component on the decoder has burnt, then the decoder is dead unless the component can be replaced - generally the answer there is 'no'.

[Bufferstop]

Quite why this is I don't know, but a German retailer gave me this advice early in my DCC journey, and it has been invaluable.)

Re-writeable read only memory (sounds stupid doesn't it) That's what decoders are, can behave in odd ways. I've had instances of Friday afternoon, updating an EPROM which has apparently failed, being tossed on the bench and left 'till Monday, only to come in and find that it has "taken" and works perfectly. Even if you give up and replace one, don't throw it away. Put it away, preferably in an anti-static bag, and have a look at it, some time in the future when you have a spare few hours and see if you can recover it.

[Geordie088]

Cheers for your suggestions guys. I will keep trying the cv8 reset. I have given it a go a couple if times but will persevere after reading this.

Just when I think I've got this hobby sussed, it comes along and bites me on the bum !!

[RAF96]

I have updated firmware before on accessory decoders and frustratingly found they would only read back as the old version, until I reset it just like a loco decoder whereupon the version now read correctly as the updated one. As you say this DCC can be fickle.

[Chops]

Great Scott. Truly, humans are the only creature that invents problems to solve.

[Peterm]

Great Scott. Truly, humans are the only creature that invents problems to solve.

You think!! You should have seen our old dog trying to decide which way round to lie in his bed. This was after he'd made a right mess of it to start with. I think he spent more time going round in circles than he did lying down.

[Chops]

Well, perhaps not.

[nigelwright7557]

It depends on what got damaged, the loco or the DCC controller.

Your controller should have over current protect but I dont know for certain.

A visual inspection of loco pickups and wiring should show if its ok or not.

[BromsMods]

I think the scenario depicted by the OP illustrates the importance of having some form of circuit protection between the DCC controller and the track in order to reduce the impact of short circuits. If you spend a reasonable amount of money on a DCC system then it seems only reasonable that you take steps to protect it and buying something like the DCC Specialities PSX (which I have always found extremely reliable) for a relatively small amount (compared to the cost of replacing a damaged system).

It would also help if we knew the make of decoder installed in the 121 and whether attempts to reset the decoder have been done on a programming track or on the main.

Regards
JR