I hope this hasn't been asked before but if so, sorry !!

I have a loco (Bachmann K3) which, for some unknown reason, has refused to answer to my calls.  Whilst I didn't buy the loco "DCC Fitted", to my surprise, it came as such but I'm not sure which decoder is installed.  It worked fine until yesterday and, rather stupidly, I'd never recorded the decoder manufacturer.

I have removed the errant decoder pending further examination and have temporarily fitteds a brand new Zimo MX600R (the loco has an 8 pin socket).

Having changed the address from the factory "3" using my Zimo MXULFA programmer, and, because the forward/reverse needed switching, I also altered CV 29 from the existing "14" to "15" (thus, I thought, changing Bit 1 from 0 to 1).

The travel direction was now correct but, going forward, the loco was well under control, however, in reverse, it took off at the speed I get up each morning ……………. :roll:   On the first notch of the throttle, it takes off like Usain Bolt.

Ah thinks I …………  I'll just do a factory reset - CV 8 to 8

It hasn't made any difference - it still can't wait to get to the engine shed - in reverse !!  forward, it does as I instruct.

Any ideas please chaps ……………………?


On edit - it has just occurred to me, as I type this away from the layout so can't check - what would be the situation if I'd plugged the thing in backwards ?  There are no markings on the socket to show me Pin 1 so it could be that the plug simply needs reversing.  This might correct the travel direction but would it also bring the loco under control when reversing ?   :hmm

Hi Peter,

rather hard to comment on the fault other than to observe that if it happens with two different chips that makes it unlikely to be their doing, could it be the controller by any chance?

Also pull out the Chip, install a blanking plug and test on DC, both fwd and reverse.

Manufacturer info is stored in the CV value of  #8, setting that to 8 triggers a reset (if it works) but then reinstates the manufacturer's ID. You can check if the reset has worked by reading some known CVs

Beyond that not very helpful input, I'm "diagnostically destitute".

Sounds similar to what happens if you have DC enabled in CV 29 and you get a short somewhere Peter.

But why on earth you would get a short in only one direction, I've no idea  :???:





Ed

Thanks for your input chaps.


Having quickly checked this morning, I had plugged the decoder in the wrong way round.  
Pin 1 was indeed marked on the socket but the digit was hidden behind something looking like a miniature electric fire element …….. :hmm

I also noticed the capacitor hadn't been removed - ought I to do so ?

I haven't had time to do a reset and test this morning but will do so shortly.

OK - an update …………………. :roll:

I plugged the decoder in the correct way around with the result that the direction of travel is now correct.  I also removed the little yellow capacitor which I understand, is not required for DCC running.

I have no idea what those little "electric fire element" things are - shock absorbers ( :roll: :roll:) - but I noticed one had come adrift at one end.  I resoldered that and re-fitted the Zimo MX600R decoder.

Same thing - perfectly controllable running forward but like a bat out of hell in reverse………….

Following Colin's suggestion, I replaced the chip (decoder) with a blanking plate and tested it on DC.  Ran perfectly in both directions !!!!   :???:

The only other option I can think of is to try a different decoder on the loco although I only have 1 brqand new one left to try - a Zimo MX 635.  I don't really want to try one I've taken out of another loco because the liklihood is that I removed it for some reason !!  I can only "play" with Zimo decoders because that's the only programmer I have - the MXULFA with the MXTAPS tester.

Any other bright ideas ?   :hmm :hmm :hmm

It's possible there may be a short on the DCC socket in the loco. Do you have a multi-meter? In which case I would remove the decoder and use the meter to check that none of the outer pairs of pins are live to each other. This can happen if the wires are soldered to the socket and an overflow has bonded them together.
 
Any such short would have no effect on DC because that's just what a blanking plug does - connects the pickups directly to the motor.

If the loco does not have lighting functions (which I suspect it doesn't) then it does not matter which way round the decoder is fitted. As you have found, it only means the direction of travel is wrong. 

Another thing to try is not pushing the decoder right in as the pins might be touching the chassis. 

Thanks for your suggestions Robert.

As those who know me are aware, I'm a bit of a 'plug and play' merchant and not into the dark art of electronics, however, maybe those who practice such witchcraft could explain the following -

On my Zimo test bed - MXULFA programmer plus MXTAPS decoder tester - I couldn't for the life of me get the thing to come under control in reverse using any decoder although it performed perfectly forwards each time.  I'd had enough and decided I'd just run it forward until I could seek repairs.  The decoders worked perfectly out of the loco and the loco ran perfectly on DC.

I reassembled everything using the Zimo MX 600R decoder.  Placing it on the track, it performed perfectly in both directions !!!  Go figure that one !

Whilst I bought the loco as a brand new model,  I'm certain it was 'pre-owned'.  I didn't fit a decoder but someone did - a cobbled together decoder where the 8 pin plug had been soldered to the decoder wires, the join covered with heat shrink sleeving but no attention paid to colour protocol.  Additionally, the tender coupling is very suspect and had definitely been removed previous to my ownership. 

I won't name the supplier but they won't get any more business from me !

I can't read anything on the duff decoder so have no idea what it is.

[user=6]Petermac[/user] wrote:

Thanks for your suggestions Robert.

As those who know me are aware, I'm a bit of a 'plug and play' merchant and not into the dark art of electronics, however, maybe those who practice such witchcraft could explain the following -

On my Zimo test bed - MXULFA programmer plus MXTAPS decoder tester - I couldn't for the life of me get the thing to come under control in reverse using any decoder although it performed perfectly forwards each time.  I'd had enough and decided I'd just run it forward until I could seek repairs.  The decoders worked perfectly out of the loco and the loco ran perfectly on DC.

I reassembled everything using the Zimo MX 600R decoder.  Placing it on the track, it performed perfectly in both directions !!!  Go figure that one !

Whilst I bought the loco as a brand new model,  I'm certain it was 'pre-owned'.  I didn't fit a decoder but someone did - a cobbled together decoder where the 8 pin plug had been soldered to the decoder wires, the join covered with heat shrink sleeving but no attention paid to colour protocol.  Additionally, the tender coupling is very suspect and had definitely been removed previous to my ownership. 

I won't name the supplier but they won't get any more business from me !

I can't read anything on the duff decoder so have no idea what it is.

Hi Peter

My apologies - as usual I am a bit late on parade.

I am glad that the loco is now working satisfactorily even if you do not know the cause of the original problem.

From what you have described, I suspect the PCB has been corrupted either at the factory or as a result of the previous owner. If the problem re-occurs you may want o consider hard wiring the decoder.

To avoid potential damafe to the decoder, if the loco were on Granby, I would be doing this right now. It is a very simple process. Remove the PCB (decoder socket) completely and join the red and black decoder wires  to the two feeds from the track and the Orange and Grey decoder wires directly to the two terminals on the motor.

Best wishes

[user=6]Petermac[/user] wrote:

I won't name the supplier but they won't get any more business from me !

I can't imagine that it was deliberate action by the company per se but perhaps an illicit and undetected swap was done on them by some person unknown. Also in a high volume business they don't have the luxury of fully checking every item they dispatch.


End result, you got unlucky, pity you didn't spot it straight away, they could have fixed it up for you.

This is not the first DCC socket issue to come up on here and the various advice received should see you right.

I think you're probably right about hard wiring the decoder John - a good call and I will indeed do so before I run it again.   :thumbs

If there is a problem with the socket, that could have blown the old decoder and could explain why the loco wasn't "new" when I bought it - possibly returned for repair and, being virtually new, got mixed up with their new stock.  I do wonder if my running it in on DC for half an hour each way did any harm …………… :hmm    It was only when I opened it up to fit the decoder that, to my utmost surprise, I saw there was already one there.  That's when I realised I had a "used" loco on my hands but that was some time after I'd actually bought it.  Except for that "odd" tender draw bar, which I assumed was a manufacturing fault, everything looked new.  Trying to return it then would have been a "my word against theirs" if they had indeed intended to off load it plus, as it ran well, I just thought I'd won a bonus decoder.

The loco was bought at a heavily discounted price Colin - not from one of the box-shifters.  There was a time when many retailers found themselves over-stocked on some Bachmann locomotives and, presumably having been given the OK from Bachmann, heavily discounted them to off-load.  I bought 2 tender locos for a tad over the price of 1 from the same retailer.  From my comments above, you'll see there was nothing to suggest they were anything but brand new until I opened this one up.