Kernow D600 Warship

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gppsoftware
Posts: 195
Joined: Thu Mar 09, 2006 5:34 am

Re: Kernow D600 Warship

Postby gppsoftware » Fri Jul 05, 2019 1:55 pm

I note you say you have tried many different CV settings to eliminate the jerking. My model did the same thing as yours in relation to jerking until I adjusted CVs 54 & 55 to the value of 10 which are the recommended settings that Kernow advise for a Loksound 4. Mine is fitted with a Bachmann 36-557 decoder (essentially an ESU Lokpilot) and those settings work with that as well. Not suggesting that you haven't already tried it but if you haven't, that may work. As for bridging the polyswitch, I would suggest total removal of the polyswitch and bridging the two points where it was soldered to the pcb with a short piece of wire.


I have indeed tried 54 and 55 set to 10 - thanks for the suggestion - these are the recommendations put out by SWD to Kernow. These were my first efforts at resolution a few weeks ago. I actually found higher values gave 'better' results.

I have now removed the polyswitch and replaced it with a strip of wire on the motherboard. Same as my video where I bridged it, the loco barely has enough power to move itself, but if you push it, the wheels do revolve. In the opposite direction, they do not turn at all.

This evening, I have disconnected the track pickup wires from the motherboard and the motor connections and have wired them into a temporary 8 pin socket so that I could fit one of my 8 pin plug Lokpilots and bypass the motherboard. This is effectively wiring the motor directly to the decoder.
Same results as before with no motion. The motherboard is not the issue.

Looking at the motherboard, the polyswitch is wired in series with the pickups ie between the track and the decoder, which means it has the potential to corrupt a DCC signal. However, since my direct connection removed the motherboard completely, I have now concluded that these motors are simply incompatible with ESU decoders. I can't believe that someone actually thought these motors were a good idea! I concede that they are great for those of a DC persuasion, but hopeless for those of us in the DCC pond.

I have also now dismantled the loco to see what space is available for the motor. It has some tiny brass fly-wheels fitted - what is the point of such small fly-wheels - they are so small that they probably have negligible effect. Another bad design in this loco.

I'm going to research for a suitable sized Mashima-type motor to replace the rubbish motor this loco is fitted with. There seems to be a reasonable amount of space and certainly extra space can be made with a small amount of diamond cutting of the chassis block. Although I question why I should be doing this on a model of this price!

I am of the opinion that Kernow have made a really poor choice of motor.

gppsoftware
Posts: 195
Joined: Thu Mar 09, 2006 5:34 am

Re: Kernow D600 Warship

Postby gppsoftware » Sat Jul 06, 2019 3:38 am

I did some more experimentation last night.

Having installed an 8 pin socket which took the motherboard out of the equation and trying an 8 pin lokpilot in it, I decided to try a DCC Concepts Zen decoder which I temporarily borrowed from another loco.
This is the first time I have seen this loco work on DCC. It actually ran reasonably well. A bit jerky, but a massive improvement on before.
With a bit of CV adjustment, I managed to get it to run better, but it still wasn't as good as on straight DC where it is very quiet. On DCC, the motor is a bit 'buzzy'. I don't think this is the fault of the decoder.

At a guestimate, I'd suggest that this loco probably requires something like an old TCS decoder without BEMF control or a decoder where BEMF can be turned off.
It seems that decoders are unable to properly control the motor because they can't monitor the BEMF properly. Could it be that this type of motor just doesn't produce the amount of BEMF that decoders are designed to expect ?

Either way, I think I have now got to the root cause of this. It isn't the decoder and it isn't the motherboard or the polyfuse causing a problem. That fact is that the motor is a very poor choice and is simply incompatible with a number of decoders, certainly including one brand of high-end decoders - ESU.

How many other locos with this same motor have hit the market ? Do others have problems with them ?

My personal opinion is that we seem to be seeing a repeat of what used to happen in the 1980's where various attempts were being made to get better results out of straight DC control. Trouble is, I think the particular model in question has taken this to the point where it is to the detriment of DCC control and incompatible.

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Metadyneman
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Joined: Wed Apr 11, 2007 9:09 am
Location: Portslade-by-Sea East Sussex

Re: Kernow D600 Warship

Postby Metadyneman » Sat Jul 06, 2019 6:09 pm

Judging by the problems you have encountered with your model and the fact that I haven't come across anyone else with the same problems (yet), I would perhaps suggest that you have been unlucky in receiving one that would appear to have been faulty from the word go. My model has worked faultlessly ever since the polyswitch issue was sorted and will run beautifully at all speeds and in either direction. It was myself and a handful of others on RMWeb who by trial & error one afternoon identified and solved the mysterious cutting out problem and everyone seemed happy once that problem had been ironed out, so I can only assume that your problem is/was a separate issue in addition to the errant polywsitch.
A voice from the distance said unto me "Smile, things could be worse" so I smiled and lo, things did get worse!

gppsoftware
Posts: 195
Joined: Thu Mar 09, 2006 5:34 am

Re: Kernow D600 Warship

Postby gppsoftware » Sun Jul 07, 2019 5:34 am

Hi Metadyneman,

Metadyneman wrote:Judging by the problems you have encountered with your model and the fact that I haven't come across anyone else with the same problems (yet), I would perhaps suggest that you have been unlucky in receiving one that would appear to have been faulty from the word go. My model has worked faultlessly ever since the polyswitch issue was sorted and will run beautifully at all speeds and in either direction. It was myself and a handful of others on RMWeb who by trial & error one afternoon identified and solved the mysterious cutting out problem and everyone seemed happy once that problem had been ironed out, so I can only assume that your problem is/was a separate issue in addition to the errant polywsitch.


I think there are two issues at play, one being the polyswitch and the other being a general incompatibility with some decoders. I did see the polyswitch cutout issue occur a couple of times on my model.

I don't actually believe that my loco is faulty.

By rewiring the loco with a temporary 8 pin socket, I have removed all the variables such as the potential for a faulty motherboard and the polyswitch. That left me with a situation of directly connecting decoders to the motor. What I found was that I had a number of ESU Lokpilots and Loksound's in stock and not one of them would work. They all happily work in other locos 'out of the box'.

My conclusion is that the motor in this loco is simply incompatible with ESU decoders, which I find rather staggering since these are top-of-the-line decoders!. I am aware that some people have got them to work, but those I have been in contact with have all said that they can't stop the jerky behaviour completely.

In a 'nutshell', the problem with this loco is the motor - it is a poor choice which evidently, some decoders can't read the BEMF from to be able to control it properly. It just so happens that I use a lot of the brand that it doesn't work with!

If I had a faulty motor, it wouldn't work on DC - it actually works extremely well on DC. I can't see how a motor can be perfect on DC control and 'faulty' on DCC control. It either works or it doesn't. I believe that the PWM and BEMF used by ESU decoders is incompatible with this motor. It would be interesting to know if our DC friends with feedback controllers have any issues. My theory is that they probably have to turn feedback off.


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