GWR City Class Killarney - horrible "surging" - Chip recommendations?

[NedFlanders]

Hi all,

On of my favourite purchases over the last year was a Bachmann GWR City Class. I only ran it on the Analog loop and it ran perfectly fine.
(image From SimonsTrains website)


Over Christmas I decided to fit a DCC chip to it as I was retiring the Analog loop.

When I opened it I found a 21 pin socket - going through my box of bits I found a DDC Concepts 21 pin decoder I had never fitted to a Irish Rail model so I thought I was sorted.

It has Horrible surging with it. Really awful. I tried adjusting the Back emf etc. - If I disabled the Back EMF it ran fine on the flat but shot down the hills and slowed right down going up.

My questions are - do Bachmann prefer certain types of chip? does anyone else have one of these with a chip fitted with good results?

Thanks

Ned.

[Bigmet]

Don't have any experience with the DCC concepts product, but the problem description is of a decoder that has too coarse a BEMF regime for the small motor in this model. Do the decoder instructions show any CV's that allow adjustment of the BEMF sampling and output, so that you can experiment for the optimum settings?

If not, I would obtain a Zimo MX638D (21pin decoder) and use that. I use only Lenz and Zimo decoders in my steam models, and they all run superbly, never yet had even a 'slightly less than optimum' result.

Decoder choice particularly matters in the Bachmann steamers, because with a few exceptions the motor used is a very efficient small 3 pole design, which starts on next to no current and is very responsive. To get the best from it the BEMF sampling frequency needs to be high rate, and the applied corrections small. (Hornby steam models with the large 'black can' five pole skew wound motor aren't nearly so sensitive by comparison.) I have a good number of Bachmann steam models that will have motors identical or similar to your 4-4-0: C class, J11, K3, O4, 3MT, Ivatt 4MT, BR std 4MT 2-6-0, etc. and all perform beautifully with whatever Lenz or Zimo decoder they are fitted with.

[Ironduke]

does the loco have any EMI suppression components on the board? i.e capacitors and chokes?

[Mike Parkes]

I find Lenz decoders work well in Bachmann steam locos and a cheap dodge adopt the 21pin blanking plug to wire a 8pin Lenz Standard to - £18 from Model Railways Direct.

[NedFlanders]

Thanks for your replies,

i have pulled out the chip box again - its a DCC concepts Zen Z218
its replacement on the dcc concepts website - https://www.dccconcepts.com/product/zen ... functions/

Details from a retailer https://www.dckits-devideos.co.uk/index ... uct_id=456
Which says it has - Back EMF with step-variable or Fn button control. ( I'm afraid that is not a language I speak)


Bigmet - that sounds interesting - I did look through the manual of the chip but I couldn't get any joy with my changes. I will take another look when I get a chance - work is getting in the way at the moment - it took me over a month to ask the question.

IronDuke - I couldnt get the body off the chassis - looking at the manual for the loco it should be possible - but I think the reality doesn't match the manual. I could only see destruction in my future when I went at it.

Thanks - Mike - I'll look at those.

[Bigmet]

I find Lenz decoders work well in Bachmann steam locos and a cheap dodge adopt the 21pin blanking plug to wire a 8pin Lenz Standard to - £18 from Model Railways Direct.

Back in the day when the Lenz Standard was comfortably the class leading low cost decoder, I was doing likewise; though my approach was remove 21 pin socket and hardwire (to the tender underside socket if available).

The advent of the price competitive Zimo MX638 21 pin decoder has ended that. A whole £1 extra and it just plugs in. Surprised that Lenz haven't made the obvious move of offering their Standard in 21 pin format at the same price point: quite possibly sales of the circa 60% higher priced Silver 21pin are very profitable for them, no need to rock that particular boat...

...Details from a retailer https://www.dckits-devideos.co.uk/index ... uct_id=456
Which says it has - Back EMF with step-variable or Fn button control. ( I'm afraid that is not a language I speak)...

I read that as the authentic brown stuff available from any equine. There's nothing like a manual written in plain English. Zimo's are good; when work permits download one, and read the explanation about the CV's to adjust sampling frequency and feedback intensity with a neat little explanation of the whys and wherefores, and optimisation for coreless as compared to iron core motors. That last is going to be of increasing importance, as coreless motors become more common in OO.

[NedFlanders]

Don't have any experience with the DCC concepts product, but the problem description is of a decoder that has too coarse a BEMF regime for the small motor in this model. Do the decoder instructions show any CV's that allow adjustment of the BEMF sampling and output, so that you can experiment for the optimum settings?

During lunch I found the 49 page manual on the dcc concepts website - this section looks promising relative to what you were saying.

Use CV66 to adjust the overall influence of BEMF on your locomotive running characteristics: DCCconcepts ZEN BEMF is pre-set & automatically adjusts for many motor types so generally needs little adjustment. However, some very low current or coreless motor types have significant differences so we have created a second BEMF range to accommodate them.Default of 0 in CV66 will leave the main BEMF structure active. This is suitable for most motor types. If you set CV66 to 1, it will lower the influence levels of BEMF, making them suitable for very small, high efficiency or coreless motors. You can also turn BEMF off OR control BEMF on/off via a function button by setting the appropriate numbers into CV61 OR keep BEMF active only for starting locomotive / turn it off at a specific speed step with CV10.

Whereas I suspect I was just going at CV10 as this sounds familiar to what I was doing.

In this case the default of 0 equals ex-factory pre-set. We recommend you leave it at default unless you really need to adjust it. The value you enter into CV 10 directly correlates to the speed step at which he BEMF action will greatly reduce and/or cut out. For example, if you want to use BEMF to aid starting, but keep direct control (without automatic speed control on gradients for example) for the rest of the speed range, use CV10. To adjust when BEMF stops acting, simply enter any value into CV 10 that is between 1 and 128. The number you choose will then be the speed step at which BEMF stops acting on your locomotive

I might just put the boards up and give it a lash this evening.

Cheerio

Ned.

[Bigmet]

... If you set CV66 to 1, it will lower the influence levels of BEMF, making them suitable for very small, high efficiency or coreless motors...

That's one to try.

Did you find anything on the sampling rate? If there is a CV setting for higher frequency sampling available, also worth trying.

[NedFlanders]

Unfortunately the manual on the dcc concepts site did not match the chip ( to be fair - the manual wasn't specific to the chip, it was a generalised one)

Hornby Railmaster detects the chip as a zmini and cv 66 is unavailable.

I scrolled through all the cvs to see was there anything relating to what you were saying bigmet but nothing lept out at me.

Time for a spot of 21 pin window shopping.

Thanks all.

Ned.

[Bigmet]

It is worth mentioning at this point that my view of DCC is as a utility; I want the desired level of performance for the least expenditure.

I had very satisfactory operation from a good quality DC set up (Morley controllers) when I tried DCC near 20 years ago, and was instantly 'sold' by the far greater operational liberty that DCC provided, and the ability to match decoder settings to the very varied collection of mechanisms I was operating. The only rub was the price of decoders, at the time the best part of £30 for good decoders, which after trialling everything then available meant only Lenz or Zimo would do in steam mechanisms. Lenz decoders for the good mechanisms, and a few (of the yet more expensive) Zimo as 'mechanism tamers', which have 'moved on' over the years as the less than wonderful mechanisms have been rebuilt or replaced to a standard which the Lenz decoders could handle.

Then came the day that Lenz introduced their standard decoder at well under £20, that was better! And a good many years later Zimo with their MX6xx range at a competitive price point, there's handy. But I would much rather only spend £5 a throw on decoders: so if you ever find a decoder that matches these two brands for a lot less money, do tell...

[NedFlanders]

Time for a spot of 21 pin window shopping.

Thanks all.

Ned.

Its that the time?.....

I went shopping - took all the sage advice and picked up a Zimo MX638D, and then left the railway, locos, etc. sitting dormant for 6 months.

Anyhowdy - I fitted the Zimo chip during the week, got the railway out and the surging is gone now.

The loco mightnt be the greatest runner at the moment ( no nice slowdown to stop, etc.), but I have high hopes with how its behaving with the chip "out of the box" with the its previous errant behaviour gone. Thanks for the pointer BigMet.

Cheerio all.

Ned.

[Bigmet]

Well that's good!

...The loco mightn't be the greatest runner at the moment ( no nice slowdown to stop, etc.), but I have high hopes ...

Some much larger values than the factory settings in CV3 and CV4 will fix that.

Tastes vary in operational style, and one of the 'liberties' that I found so engaging in the DCC package, was how it enabled me to watch the trains perform, rather than having to 'drive'. With large settings in CV's 3 and 4, you can just watch as the loco slowly grafts up to speed, or glides to rest over a very extended distance. Good decoders are inch perfect in such; set speed step to zero at a 'mark' on the layout, and it will decelerate gradually to halt a couple of inches off the stops, every time.

[Dad-1]

It's all fixed now, but I recall having a Bachmann 21 pin decoder in a small Bachmann steam loco
and it just jerked about, couldn't get it to run. It required two of the BEMF setting changed and
If I remember correctly the suggested values were on the Bachmann website - somewhere.

I do tend to use Zimo on anything with problems and never been disappointed.

Geoff T.

[Bigmet]

It's all fixed now, but I recall having a Bachmann 21 pin decoder in a small Bachmann steam loco
and it just jerked about, couldn't get it to run. It required two of the BEMF setting changed ...

That was the badged ESU lokpilot v1 that Bach offered in 8 pin and 21pin (36-553/554). Very tweaky BEMF setting in CV's 54 and 55 required to alter the sampling and feedback for small motors. It also lacked a large enough range in CV's 3 and 4 for steam locos for my taste. It was a good decoder for large centre motor twin bogie drives with heavy flywheels, still have those I purchased in use. The major attraction when introduced was the sub £10 price when Lenz and Zimo were nearer £30...

Edited to correct misremembered decoder numbers

[Metadyneman]

That was the badged ESU lokpilot v1 that Bach offered in 8 pin and 21pin (36-533/534 if memory serves).

The 21 pin re badged ESU Lokpilot v1 was the 36-554 (36-553 was the 8-pin equivalent). The latest Bachmann 21-pin version is the 36-557 which is a re-badged Lokpilot standard. The original 36-557 was a re badged Soundtraxx decoder and was awful! the two are discernable by different pcb colour (ESU =blue Soundtraxx = green)
Incidentally my Bachmann "Killarney" (which I have re worked as City of Truro) has a 36-554 in it and is and excellent runner at all speeds.