Loco will not run in DC mode after changing CV29 Value

[Deem]

Hello Everyone

I recently installed couple of Decoders in my R3086, R3171 and bought R3171 with 5 pole conversion DCC already fitted.

I have Bachmann Dynamis E Z Command Station.

After installing the decoder to 8 pin board, I would program the Decoder or run on default setting of Loco 3, issue's I am having is:

After installing 2 different decoder and one pre-installed decoder, all Loco with run in wrong direction (When I choose Forward direction Loco would go backward - When choose to go backward Loco would go Forward)

BUT and this is really strange, All Loco will work with Analogue Controller without changing anything in CV29.

Once I change CV29 value 0 to 1 Loco will run in correct direction with DCC controller but will not run with Analogue Controller now.

Any Advice will be much appreciated.

Regards

[96RAF]

Use this calculator to pick the features you want and write that decimal value to CV29.

It is the easiest way and avoids all the pitfalls of adding this number or taking away that number from the number you first thought of.

http://www.2mm.org.uk/articles/cv29%20calculator.htm

[Rog RJ]

Try setting CV29 to 7. See this CV29 calculator http://www.2mm.org.uk/articles/cv29%20calculator.htm

[Fishmanoz]

Agree with Rog. From the CV29 calculator:

• 1 = reverse direction to solve your running wrong way
• 2 = 128 speed steps, and
• 4 = DC operation

All together = 7. And the only way CV29 would have been on 0 would be someone setting it there, certainly not a default value which is most often 2 or 6.

[Jim-R855]

It all sounds very complicated, but if you know the original value from CV29 when everything except direction was working as you wanted it, just add 1 to that value to change direction, do not replace the value with 1, otherwise all you have is reverse direction enabled and all other features disabled.

If you understand binary it is quite easy to understand CV29, but most people like to think in decimal so we make life hard for ourselves by thinking of say, reverse direction and DC operation, as 5 instead of as 101.

It is said that there are only 10 types of people in the world, those who understand binary, and those who don't.

(I'm not fluent in binary, I have to run it through decimal to make sense of it, but the understanding of it really helps)

[ColinB]

Easy solution, I am assuming you don't have any lights on the loco, just turn the DCC decoder round. So insert it in the socket the other way round. Alternatively swap over the motor connections. The trouble with changing CV values in this case, 3 months further down the line when you decide to reset the decoder you will have to do the process all over again, which by then you will have forgot.

[Deem]

Thanks all for your inputs and thoughts, really appreciate your help.

I will check and try to figure out once I am back home 🏡 because I am in Birmingham at the moment.

Very well explained in calculator.

Regards

[Fishmanoz]

Colin, swapping decoder installation in the socket is going to have a hard time making DC Operation enabled.

And given all of the shenanigans here, I doubt Deem will forget the correct CV29 value.

[Deem]

@Fishmanoz

Once I have done couple of time the CV29 process I tend not to forget but as precautions I can always save this thread and if ever I am struggling I will come back to this well thought and thoroughly explained.

[ColinB]

Sorry Fishmanoz but I am having difficulty understanding your response. Turning the decoder around in the socket has absolutely no effect on dc running as the pickup pins and motor pins are still in the right place all be it not the same polarity. Most decoders I have taken apart have a four diode bridge rectifier, which basically means on DC it should work no matter the polarity of the input signal. All that will happen is it will run backwards which is what he wants to achieve. I convert a lot of locos to DCC operation and as Hornby kindly make both wires going to the motor black when I rewire the loco for DCC I invariably get the motor wires wrong especially if I have had to take the motor out to get to the pickup wires. If the loco running in the wrong direction I generally just swap the motor wires over just because I like neatness, but I am pretty sure turning the decoder round worked equally as well. Generally turning the decoder round means the lights don't work which generally on a steam loco has no effect. If someone has wired smokebox flicker to a function, then again that will not work. Anyway everyone states if you want to run DC, pull out the decoder and put in a DC header. I have an Elite so playing with CV values is easy, on a lot of DCC controllers it is not so especially if the module has "stay alive", so I avoid suggesting it as a fix.

[Brew Man]

@ColinB

I think that was Fishmanoz's point. The OP's problem was that DC operation wasn't working after changing Cv29, so turning the decoder around will not fix the problem.

[ColinB]

Well it probably will because if changing CV29 didn't work you obviously haven't set the bit. The trouble I have found is with my Elite it quite often says it has changed a valve when it it has not. I have got to the point of counting the relay clicks, which I assume is the Elite putting power onto the programming track. This gets tons worse if you have bit of dirty track or "stay alive" fitted. It also has a habit indicating it has finished when you know it did it too quickly so has failed but not told you. Generally I always try to read back what I initially set but with the Select, I gather that is not possible.

[Brew Man]

I think it's obvious that Bit 2 has not been set as Deem said he changed the value 0 to 1, suggesting he didn't add 1 but replaced what was in there with 1.

[96RAF]

@colin

Elite programming. You are correct the relay swaps the low energy signal circuit between the Prog output and the Boost output. Proven by ‘scope monitoring of both output terminals.

Select only has a Track output so effectively programs on the main, hence there is no read-back possible (Railcom excluded - before anyone picks up on that - which is decoder dependant and controller switchable if supported - e.g. Elite turns it on as required, else off).

[Deem]

Thanks all for your explanation and support, I used the calculator and calculated value was 7, so I changed the CV29 value from 0 to 7 and everything seem to be working, Loco are running correct direction and also I can used them in Analogue (DC) mode as well. I have tried with 2 Loco and seem to resolved everything, will try with couple more Loco tomorrow and I will update further.

Regards

[Deem]

Another update, Just programmed the Hornby Cock O the North R3171 which have been converted by previous owners to 5 Pole motor and have Hornby Decoder.

Changed the CV 29 value to 7 after using calculator,

Loco runs both way in correct directions with DCC controller

Loco also work with DC controller, only issue I have is, in DC mode loco will run in wrong direction.

What AM I DOING WRONG? Please advice if possible.

Regards

[96RAF]

You are doing nothing wrong. The loco is physically wired wrong for DC operation so you have told DCC to compensate and swap that over electronically.

The only resolution is to swap the motor wires over to get it right on DC and then make CV29 to value 6 for normal DCC running.

[ColinB]

Which is what I said about 5 posts ago.

[Fishmanoz]

Deem, without worrying about who said what to whom about it in this and your other topics where it has been mentioned earlier, the way a loco runs in DCC is first determined by which way around you connect the orange and grey wires to the motor. Then you seem to be relatively consistently wiring them the incorrect way.

You have two ways of fixing the issue - swap orange and grey or add 1 to CV29.

Then you have 2 ways of swapping orange and grey - swap them at the motor connections by resoldering, or turn the decoder around in the socket such that decoder pin 1 goes into socket 5 instead of socket 1. Having it in the socket incorrectly only affects functions and loco lighting, not often required on a steam loco.

But note, using the wrong way around method achieves what you want for DCC, but the loco will now run in reverse on DC.

If I were you, I would be making sure both decoder insertion and orange/grey wiring are correct in the first place. Then the problem won’t occur. Start by checking out the correct 8-pin plug and socket configuration via the Brian Lambert link to them and be doubly sure you have the decoder in the socket correctly in the first place. Then and only then, reverse the orange/grey connections if running the wrong way (or wired correctly to the motor if not using a socket).

For all conversions, check this before and after testing the decoder on default 03 and changing the address to the one you intend to use permanently (changing loco address has been known to affect CV29 value on occasion, even though it shouldn’t). Do it all before re-installing the body.

Now the correct value for CV29 will be 6 if you want to be able to run on DC, or 2 if you don’t. Remember that not allowing DC running will also ensure your locos won’t be subject to DC Runaway, the uncontrolled running flat out on DCC when the decoder incorrectly interprets a distorted DCC signal to be DC.

I would use this procedure on your currently converted locos running the wrong way as well as any future locos you convert.

[ColinB]

I hate to say this Fishmanoz, but when was the last time you saw an orange and grey wire in a Hornby loco. Generally the two wires going to the motor are black, well definitely in all steam locos I have. I have fixed many Hornby locos and this is generally the case. I have never checked on diesels as generally I am not fixing those. So yes I agree if the direction is wrong swap the motor wires around, I would suggest at the motor end as it is generally easier and safer. As I said in an earlier post half the issue is that both wires are black so if you do anything to the motor there is a 50% chance you will get it wrong. I think perhaps the author should have a long hard think and decide whether they are running DCC or DC as generally if a decoder is fitted it is not a good idea to run DC. I sometimes run a DCC loco on DC if I am testing it out and I can't be bothered to setup DCC, but generally I am not bothered which way it goes in DC. As both functions are controlled by the software in the decoder, I would expect the loco to go the same way in DCC and DC, but it is entirely dependant on who programmed the software.

[Deem]

@Fishmanoz

I haven't done any wiring on any Loco I have or bought, this is to answer your suggestion. ("Then you seem to be relatively consistently wiring them the incorrect way.")

All I have done is installed a decoder in PCB Board which came pre wired from Hornby in DCC ready Loco's, making sure orange wire on Decoder is in Pin 1.

Hornby R3171 Loco (Cock O the North) I bought from eBay came with 5 Pole motor conversion already done without Flywheel (instead of 3 Pole motor with flywheel) and that's the Loco which is running in wrong direction only in DC (Analogue) mode. Obviously I will check after I have repaired and completed Hornby R2675 I am working on right now with squeaky sound in forward direction.

Will update in day or 2.

@ColinB

Thanks for your input and I am little bit fussy when it comes to my stuff and I tend to go quite a length to have my things in fully working order. That's just me, this also helping me to learn at the same time the in's and out of DCC - DC for which I am very grateful for my fellow Modeller.

Regards

[ColinB]

@Deem funny that someone would take the flywheel out, if you use the Pendolino motor it has two shafts so it is a straight swap. I did worry at the time that the Pendolino motor would be too fast but it doesn't seem to be.

[Deem]

@ColinB, are you talking about this motor

https://www.ebay.co.uk/itm/X9712-Hornby-Spare-Motor-2-Worm-Gears-for-Pendolino-R1076-R2467-R2467X-/304122864694?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0

Would I will have to remove both Worm? Or just one to replace with flywheel?

Regards

[ColinB]

I think when I tried it, it did work with the existing worm, but I decided just in case to use the longer worm off the original motor. I assumed that Hornby must have used the longer worm for a reason, although of late I am beginning to wonder. The good thing about those pendolino motors is they are relatively cheap compared to other Hornby motors.

Mod note - your two duplicate posts removed Colin.

[Deem]

@ColinB

Thanks for sharing your thoughts will look into buying one, once have spare cash to spend.

Further update for everyone, i swapped wiring on motor which had:

Grey wire soldered at the top point on motor

Black wire soldered to bottom point on motor

I swapped them around, reprogrammed with DCC,

Changed the CV 29 value to 6 and thanks to all of you everything as should be.

In DCC mode correct direction and even in DC mode correct direction as well now.

Many many thanks for all the help by everyone.