bachmann J72 (new) issue

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Michaelaface
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bachmann J72 (new) issue

Postby Michaelaface » Thu Feb 25, 2021 2:49 pm

hello forum, was wondering if any of you have any ideas as to how I could solve an issue I'm having with my J72
it runs perfectly on DC and on DCC on a rolling road, everything is clean, the track is clean, no issues, except when I place the loco on the track, the decoder will constantly reset making running impossible

would a stay alive solve this? or is there something else I'm missing here

here is a link to a video that demonstrates the issue

https://youtu.be/UVnij82TZs0

thanks
Michaela

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Mountain
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Re: bachmann J72 (new) issue

Postby Mountain » Thu Feb 25, 2021 4:18 pm

Easy! Dissable the inertia settings on the decoder and possibly the back EMF as well. Set the value to 0 or whatever is the setting that turns them off.

What is happening is that slight interuptions of the track to decoder (Track to motor if it was DC) which would be so slight that they would not be noticeable with DC are enough for the decoder to assume that it has to start the inertia again as the decoder thinks that due to the fraction of a second it has no power, that the locomotive is starting from stationary so it starts the inertia all over again.
Now stay alive will overcome this OR switiching off the inertia setting.

With locos that have more pick-ups with their wheels especially diesels with all wheel pick up along with larger steam locomotives, they are far less likely to get this issue, but small shunting locos, especially if they have split chassis can have these little pickup interuptions which can baffle DCC users. When I first started with DCC only the most expensive decoders had inertia so few of us had them, however when most decoders starting having inertia and we were needing to hard wire older models, these issues started to present themselves.

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Thu Feb 25, 2021 5:28 pm

Mountain wrote:Easy! Dissable the inertia settings on the decoder and possibly the back EMF as well. Set the value to 0 or whatever is the setting that turns them off.

What is happening is that slight interuptions of the track to decoder (Track to motor if it was DC) which would be so slight that they would not be noticeable with DC are enough for the decoder to assume that it has to start the inertia again as the decoder thinks that due to the fraction of a second it has no power, that the locomotive is starting from stationary so it starts the inertia all over again.
Now stay alive will overcome this OR switiching off the inertia setting.

With locos that have more pick-ups with their wheels especially diesels with all wheel pick up along with larger steam locomotives, they are far less likely to get this issue, but small shunting locos, especially if they have split chassis can have these little pickup interuptions which can baffle DCC users. When I first started with DCC only the most expensive decoders had inertia so few of us had them, however when most decoders starting having inertia and we were needing to hard wire older models, these issues started to present themselves.


nope this hasn't solved it (unless I'm doing the wrong thing here) CV3 I can't really set to 0 because its a sound loco, and CV10 (back emf) doesn't exist on this decoder, plus even with CV3 on 0 the performance is still stop constantly stop start

Bigmet
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Re: bachmann J72 (new) issue

Postby Bigmet » Thu Feb 25, 2021 5:53 pm

A stay alive is a 'band aid', the fundamental problem that should be addressed is interruption in the track supply to the decoder. Do all pick up wipers maintain full contact through side to side movement of the wheels? Are all the connections from the pick up strips to the decoder sound? (Bachmann have gone for a production line expedient (my opinion) by using sprung contacts to connect the internal wiring to the pick up strips, instead of soldered joints. Any hint of trouble in power reaching the decoder, and I solder the wires to the pick up strips. Now, I haven't seen a new J72, but this method has been utilised on all their last 10 years of new steam introductions that I have looked at.)

There are decoder settings worth looking for in case your decoder has them: a 'time out' interval which is imposed when the decoder loses track supply, that can be set to zero; and whether or not the decoder reapplies the CV3 value after a power interruption, or resumes at previous speed step.

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Mountain
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Re: bachmann J72 (new) issue

Postby Mountain » Thu Feb 25, 2021 6:33 pm

Michaelaface wrote:
Mountain wrote:Easy! Dissable the inertia settings on the decoder and possibly the back EMF as well. Set the value to 0 or whatever is the setting that turns them off.

What is happening is that slight interuptions of the track to decoder (Track to motor if it was DC) which would be so slight that they would not be noticeable with DC are enough for the decoder to assume that it has to start the inertia again as the decoder thinks that due to the fraction of a second it has no power, that the locomotive is starting from stationary so it starts the inertia all over again.
Now stay alive will overcome this OR switiching off the inertia setting.

With locos that have more pick-ups with their wheels especially diesels with all wheel pick up along with larger steam locomotives, they are far less likely to get this issue, but small shunting locos, especially if they have split chassis can have these little pickup interuptions which can baffle DCC users. When I first started with DCC only the most expensive decoders had inertia so few of us had them, however when most decoders starting having inertia and we were needing to hard wire older models, these issues started to present themselves.


nope this hasn't solved it (unless I'm doing the wrong thing here) CV3 I can't really set to 0 because its a sound loco, and CV10 (back emf) doesn't exist on this decoder, plus even with CV3 on 0 the performance is still stop constantly stop start


Ah. It was worth a try.

Rollers are great but are rather like a bicycle repair stand where one can get the bikes perfectly set up on the stand, but would need to do further adjustments when riding them.

Check, clean and adjust (If needed and if possible) the locos pickups and wheels...

But it is a puzzling problem...

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Thu Feb 25, 2021 6:33 pm

Bigmet wrote:A stay alive is a 'band aid', the fundamental problem that should be addressed is interruption in the track supply to the decoder. Do all pick up wipers maintain full contact through side to side movement of the wheels? Are all the connections from the pick up strips to the decoder sound? (Bachmann have gone for a production line expedient (my opinion) by using sprung contacts to connect the internal wiring to the pick up strips, instead of soldered joints. Any hint of trouble in power reaching the decoder, and I solder the wires to the pick up strips. Now, I haven't seen a new J72, but this method has been utilised on all their last 10 years of new steam introductions that I have looked at.)

There are decoder settings worth looking for in case your decoder has them: a 'time out' interval which is imposed when the decoder loses track supply, that can be set to zero; and whether or not the decoder reapplies the CV3 value after a power interruption, or resumes at previous speed step.


I've dismantled the loco and cleaned and checked every contact again (just to be sure) and everything is good, the sprung contacts are all in good condition and making their relevant contact (I quite like the sprung contact design, makes maintenance a lot easier)

looking through the CV list from the decoder manufacturer I can't see anything relevant (D&H decoder) I've also chucked locoman (sound provider) an email asking about it

link to the CV info

https://doehler-haass.de/cms/media/pdf3/SD18A_SD21A_en.pdf

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Ironduke
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Re: bachmann J72 (new) issue

Postby Ironduke » Thu Feb 25, 2021 8:47 pm

Michaelaface wrote:here is a link to a video that demonstrates the issue

https://youtu.be/UVnij82TZs0


That is very odd behaviour. I suppose a rolling road makes better contact with each loco wheel via two rolling wheels, whereas on the track there is only one point of contact, but that's a significant difference in performance and you've obviously cleaned everything. The only other difference is that the loco is moving rather than standing.

Can you bypass the decoder and see how it performs on direct DC?
Regards
Rob

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Sat Feb 27, 2021 8:30 pm

Ironduke wrote:
Michaelaface wrote:here is a link to a video that demonstrates the issue

https://youtu.be/UVnij82TZs0


That is very odd behaviour. I suppose a rolling road makes better contact with each loco wheel via two rolling wheels, whereas on the track there is only one point of contact, but that's a significant difference in performance and you've obviously cleaned everything. The only other difference is that the loco is moving rather than standing.

Can you bypass the decoder and see how it performs on direct DC?


yeah it almost seems like the loco moving for some reason is causing a break in the circuit somewhere, but I'm not sure where or how, and yes I've dismantled and cleaned and lubricated everything so many times now aha

it runs fine on DC, on the half hour each direction running in it was perfect, and still runs fine now

I'm going to check the back to backs to see if there is anything in that which might be an issue

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Re: bachmann J72 (new) issue

Postby Ironduke » Sat Feb 27, 2021 11:44 pm

Michaelaface wrote:it runs fine on DC, on the half hour each direction running in it was perfect, and still runs fine now


You mean without the decoder?
Regards
Rob

Mike Parkes
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Re: bachmann J72 (new) issue

Postby Mike Parkes » Sun Feb 28, 2021 12:21 pm

If its okay on dc then its a decoder issue. Suggest you try a different decoder in it.

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Sun Feb 28, 2021 2:47 pm

Ironduke wrote:
Michaelaface wrote:it runs fine on DC, on the half hour each direction running in it was perfect, and still runs fine now


You mean without the decoder?


With and without
Mike Parkes wrote:If its okay on dc then its a decoder issue. Suggest you try a different decoder in it.


It’s the only 18 pin loco I have so I’d have to buy a decoder to try this, I’ve spoken with the supplier and I don’t think there’s any issue with it

I’m just going to try a stay alive and hope that solves it

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Thu Mar 04, 2021 7:28 pm

stay alive fitted, runs perfectly, I'm guessing I now have to avoid shorts at all costs with this loco?

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Mountain
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Re: bachmann J72 (new) issue

Postby Mountain » Thu Mar 04, 2021 7:55 pm

Shorts? Do J72's wear shorts?

I am glad it works.

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Michaelaface
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Re: bachmann J72 (new) issue

Postby Michaelaface » Thu Mar 04, 2021 9:26 pm

Mountain wrote:Shorts? Do J72's wear shorts?

I am glad it works.


only in summer

no I'm just assuming, if the loco encounters a short circuit for any reason, are the various components in the system going to register this short and protect themselves or is there a potential disaster waiting to happen

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Mountain
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Re: bachmann J72 (new) issue

Postby Mountain » Thu Mar 04, 2021 10:49 pm

I went into DCC during and just after the year 2000 and back then none of the decoders were protected against short circuit on the decoder to motor or accessory side of things, so one had to double check everything which is a good idea anyway.
It was only when basic decoders dropped to be lower priced then locomotives that I decided to invest in DCC, and to be honest, as I then moved away from 00 to model in 0-16.5 on a budget, DCC became un-neccessary for my requirements and aims, especially as I did not have much money which is why I had turned to 0-16.5 instead of 00.

I have to be honest and say that if there is something to adjust, I will spend ages adjusting it to get it as right as I can set it, so when I bought an early Bachmann DCC sound loco when they first came out, I spent soo long adjusting every setting I could (And my Lenz system could access things that I believe one can't access today so I went all out fiddling) that I sat there thinking "All this time fiddling when I could be modelling or running trains!"
I can relate to the frustrations when something does not go to plan. Having said that DCC is lovely when one gets it all going and can afford to invest in it. It is more that I tell myself "No" to save my self stress. :lol: Then I go and look at tiny radio control systems and look at my locos and dream for a few days until I come back to reality and say to myself "Keep it simple. You can do simple!" :lol:

But going back to your loco. It is a good idea to add bits of insulation so nothing will risk touching things it should not. As long as your decoder can "Breathe" so it does not get too hot... The older DCC decoders were always kept "Open" so they could diccipate heat effectively and they said not to cover them, but many of todays decoders have built on sleeves so I do wonder if the sleeved ones risk overheating? But there again, the unsleeved ones can risk shorts, so either way it is not ideal but as long as they work we are happy.


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