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Kernow Models D6xx Update


Andy Y
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Looking at the description of what a polyswitch does on the interweb, the symptoms of what is happening when the loco comes to a halt would seem to replicate what the polyswitch does. In other words it restricts the current when it gets too hot to just a bare "leakage" until it has cooled down sufficiently then it restores the current back when it cools down. Maybe the polyswitch isn't up to the job!

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1 minute ago, metadyneman said:

Looking at the description of what a polyswitch does on the interweb, the symptoms of what is happening when the loco comes to a halt would seem to replicate what the polyswitch does. In other words it restricts the current when it gets too hot to just a bare "leakage" until it has cooled down sufficiently then it restores the current back when it cools down. Maybe the polyswitch isn't up to the job!

 

I strongly believe that to be the case - with a sound decoder the current drawn is possibly just reaching the point where the switch does its job. That said, my D600 is drawing 0.1 to 0.2 amps, 0.3 amp approaching stall - I am really surprised if a Loksound 5 is needing 0.7 amp. Richard, do you know what power it is rated at? As an aside, the 1 amp switch will have a tolerance on it, without knowing the manufacturer and having the datasheet it is not possible to know what that is. If it is a poor quality component, that tolerance will be bigger and mean that the tripping out could be significantly below 1 amp.

 

Roy

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Just now, Richard Croft said:

It’s rated at 1.5 amps so should have no issues handling it, around 10 minutes in and it’s still running well with the 4 coaches which it couldn’t manage when I first discovered the problem.

 

Richard 

Good stuff.. I might just do this with mine and see what happens with yours and abandon my plans to return it to Kernow

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1 minute ago, Richard Croft said:

It’s rated at 1.5 amps so should have no issues handling it, around 10 minutes in and it’s still running well with the 4 coaches which it couldn’t manage when I first discovered the problem.

 

Richard 

 

Good news - sounds like the chosen component is not really the right specification for what it is being used for. Fairly easy fix for Kernow, if they don't need to re-certify the design - just put in, for example, a 1.5 amp resettable fuse.

 

Roy

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For future reference, the screen printing on the PCB was the give away that it was not a capacitor. 99 times out of 100, a capacitor will be marked C, resistor R, indictor L, diode D and a fuse F. That one was marked F1.

 

Roy

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Thank you both for this, I am now about to test D600 round the garden (with bridged polyswitch) and hope there are no blue puffs of smoke! This forum is excellent at times and this has proved to be the case this afternoon. Thank you gentlemen

Edited by metadyneman
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7 minutes ago, RedgateModels said:

I guess it's placement directly below the decoder was deliberate to protect against possible decoder overloads too....

 

It will do that yes, it seems to be looking for a total current draw from the loco of a maximum of 1 amp. Now, somebody said theirs is doing it on DC - that to me suggests a different fault is leading to the same issue of tripping the fuse.

 

Roy

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6 hours ago, metadyneman said:

Just as a matter of interest has anyone on here actually taken the plunge and removed the capacitor like component from the circuit board?

 

Yes, I snipped it out and everything died - both on dc and DCC. It is obviously part of the supply. I therefore bridged it with a short wire and got it working again!

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On a Loksound V5 which CV (if any) activates overload protection please, that would be helpful, or is it something that is activated anyway?

Edited by 7013
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20 hours ago, Richard Croft said:

I’ve got the same problem with mine, using a loksound 5. It ran fine on DC so I milled it out inside to fit an EM2 speaker and it sounds brilliant, whilst it’s running after a few minutes and particularly when pulling a load all of a sudden it stops, starts making a clicking noise and the lights flash, if I press stop on my controller and stop again to put the power back on it will move again, but only for a few minutes. Really disappointing, I’ve made my own sound file for it and everything.

 

Richard

Hi Richard, that sounds like the decoder is overheating and then shutting down.

 

Q1) What happens if you run it with all the light functions off? There should be a difference in run time before overheat between lights on and lights off.

 

Q2) What about the running with lights on but sound off?

 

This is starting to sound as if there is a mis-spec component on the pcb.

 

Luke

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Just now, Richard Croft said:

Hi Luke, theres been a lot of conversation around this issue today but between a few of us we narrowed it down to the orange part under the decoder which I though was a capacitor, its actually a resettable fuse which cuts out to protect the decoder, the problem is it seems to be doing it too early, I have removed it and bridged it and the issue has now gone away. I enabled overload protection with the Lokprogrammer just in case.0085B5E3-53D9-454D-9790-78E717F72708.jpeg.697aba96f088bad6525b743a4e2c7b9e.jpeg

Hi Richard, I realised that as soon as I posted! Serves me right for tring to do things on a phone from a branch of Burger King at the central railway station in Minsk (Belarus)... I'll read the rest of the posts when I get back onto the hotel wifi! Luke

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9 minutes ago, Richard Croft said:

Hi Luke, theres been a lot of conversation around this issue today but between a few of us we narrowed it down to the orange part under the decoder which I though was a capacitor, its actually a resettable fuse which cuts out to protect the decoder, the problem is it seems to be doing it too early, I have removed it and bridged it and the issue has now gone away. I enabled overload protection with the Lokprogrammer just in case.0085B5E3-53D9-454D-9790-78E717F72708.jpeg.697aba96f088bad6525b743a4e2c7b9e.jpeg

Ok, thread read!.

Until you posted the photo and Roy saw it we were stumbling around in the dark so thanks for your photo!

Looks my suggestion of out-of-spec component was correct but too late...

Knowing you can do the full sound install with EM2 and LS5 what would the total cost be? Once I'm back from holiday and been paid I'd be interested in getting my D600 done.

Thanks, Luke

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9 minutes ago, Richard Croft said:

Hi Luke, theres been a lot of conversation around this issue today but between a few of us we narrowed it down to the orange part under the decoder which I though was a capacitor, its actually a resettable fuse which cuts out to protect the decoder, the problem is it seems to be doing it too early, I have removed it and bridged it and the issue has now gone away. I enabled overload protection with the Lokprogrammer just in case.0085B5E3-53D9-454D-9790-78E717F72708.jpeg.697aba96f088bad6525b743a4e2c7b9e.jpeg

Ok, thread read!.

Until you posted the photo and Roy saw it we were stumbling around in the dark so thanks for your photo!

Looks my suggestion of out-of-spec component was correct but too late...

Knowing you can do the full sound install with EM2 and LS5 what would the total cost be? Once I'm back from holiday and been paid I'd be interested in getting my D600 done.

Thanks, Luke

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Motor Overload Protection= CV124....bit 5
Motor is not switched off when blocked.=0
Motor is switched off for a few seconds when blocked to avoid burnout=32

The introductory notes appears to indicate that overload protection is on, but is worth checking if you modify the pcb by removing the orange fuse and making a continuous join.

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Opened my front door not long ago to see a rectangular parcel waiting for me. I knew what it was but had to wait until I returned home to open it, but am not disappointed by the model. Very nice, but need to get my layout up and running so that I can see if it is not one that seems to have the issue. If it is I will be disappointed as I would probably have to send it back to Kernow all the way from Western Canada.

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9 hours ago, jsp3970 said:

Opened my front door not long ago to see a rectangular parcel waiting for me. I knew what it was but had to wait until I returned home to open it, but am not disappointed by the model. Very nice, but need to get my layout up and running so that I can see if it is not one that seems to have the issue. If it is I will be disappointed as I would probably have to send it back to Kernow all the way from Western Canada.

 

I don't think it is that there are "affected models" - simply if you use a decoder that tries to draw more than 1 amp, you will see the problem.


Roy

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On 08/05/2019 at 15:06, Roy Langridge said:

 

It will do that yes, it seems to be looking for a total current draw from the loco of a maximum of 1 amp. Now, somebody said theirs is doing it on DC - that to me suggests a different fault is leading to the same issue of tripping the fuse.

 

Roy

Hi Roy

beg to differ .....in politest sort of way:)

As I said previously - I am getting a typical PPTC type failure on DC  -I have had this with DC controllers in past -  It is just I have never noticed PPTCs being installed in locos. (Pretty sure there isnt one in the Kernow Bulleid or it would have failed when I tested with 34 coaches!!)  However I advised Kernow when I had the original problem that this was my tentative diagnosis.

Thanks to Richard getting the lid off we can see the component - Looking at designation/component it appears to be  a Through Hole, PolySwitch RXEF Series, 500 mA, 1 A, 72 VDC, -40 °C  - trip current 1A and hold current 0.5A possibly a Raychem Littlefuse?

My understanding having investigated PPTC failure in past (apologies for stating something you are probably aware of but other readers may not)  is that hold current (0.5A in this case) is the current at which it is guaranteed not to trip, and trip current of 1A is current at which it will definitely trip; and when they trip they do so open circuit. What happens in between 0.5A and 1A  is "within tolerance"!!, and once they have failed they literally have to cool down before they work again. In my view they are effective but they are not a precision device !! What is causing the tripping in my 12V DC case is the trailing load - 12 or more heavy Bachmann coaches. It does not happen with 10. The fact that Ark Royal is ok with 14 just means that the specific PPTC whilst probably in spec is more tolerant of the current drawn (there is after all at least 0.5A to play with).

Having replaced polyswitches in the past they are dirt cheap from some-one like Rapid ( around 26p each from memory - but problem is because they are so cheap you have to buy a minimum quantity - [5 for Rapid and 10 for Farnell] which bumps the price up  - so perhaps those with the problem (me included) should buy another 3 or 4 Warships to make a buy cost -effective!

As Richard found out dissing it cuts current to loco  as they are an in-series (current) component.   - As I get the same issue with DC  only with more coaches before cutting out it indicates to me that these components are possibly on the electrical input side (track pickup) side of the circuitry, and they are in possibly to specifically protect the coreless motor from an over voltage/current, I also emphasise this is only a a supposition based on my understanding that although their previous diesel had lights, a chip socket etc, that this is the first big diesel produced by Kernow with a coreless motor .

As my locos run primarily on DC I am very tempted just to put in an 0.65A hold/1.3A Trip PPTC which is the next "Littlefuse" value up - but if anyone else follows this advice they do so at their own risk especially if it is followed by a DCC chip.. Putting it in is however probably a better idea than simply shorting it out  and relying purely on the controller cutout if operating on DC. (My H&M is quite capable of powering 4 big Heljan Westerns simultaneously so it will probably deliver multiple amps to a coreless motor before tripping!)

Incidentally given the reports that the fault appears to happen on DCC with only 6 coaches trailing it also means that the DCC chips are fair chomping through the power  - i.e. the equivalent of a trailing load of 4-6 Bachmann Mark 1s !! I had not realised they were that power hungry.

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I think I get the drift of post above? Much as I am tempted to snip the little fuse join the gap and activate overload protection on my chip, as Ark Royal is working perfectly at present and has shown no further signs of problems, I will leave well alone.

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1 hour ago, lochlongside said:

Hi Roy

beg to differ .....in politest sort of way:)

As I said previously - I am getting a typical PPTC type failure on DC  -I have had this with DC controllers in past -  It is just I have never noticed PPTCs being installed in locos. (Pretty sure there isnt one in the Kernow Bulleid or it would have failed when I tested with 34 coaches!!)  However I advised Kernow when I had the original problem that this was my tentative diagnosis.

Thanks to Richard getting the lid off we can see the component - Looking at designation/component it appears to be  a Through Hole, PolySwitch RXEF Series, 500 mA, 1 A, 72 VDC, -40 °C  - trip current 1A and hold current 0.5A possibly a Raychem Littlefuse?

My understanding having investigated PPTC failure in past (apologies for stating something you are probably aware of but other readers may not)  is that hold current (0.5A in this case) is the current at which it is guaranteed not to trip, and trip current of 1A is current at which it will definitely trip; and when they trip they do so open circuit. What happens in between 0.5A and 1A  is "within tolerance"!!, and once they have failed they literally have to cool down before they work again. In my view they are effective but they are not a precision device !! What is causing the tripping in my 12V DC case is the trailing load - 12 or more heavy Bachmann coaches. It does not happen with 10. The fact that Ark Royal is ok with 14 just means that the specific PPTC whilst probably in spec is more tolerant of the current drawn (there is after all at least 0.5A to play with).

Having replaced polyswitches in the past they are dirt cheap from some-one like Rapid ( around 26p each from memory - but problem is because they are so cheap you have to buy a minimum quantity - [5 for Rapid and 10 for Farnell] which bumps the price up  - so perhaps those with the problem (me included) should buy another 3 or 4 Warships to make a buy cost -effective!

As Richard found out dissing it cuts current to loco  as they are an in-series (current) component.   - As I get the same issue with DC  only with more coaches before cutting out it indicates to me that these components are possibly on the electrical input side (track pickup) side of the circuitry, and they are in possibly to specifically protect the coreless motor from an over voltage/current, I also emphasise this is only a a supposition based on my understanding that although their previous diesel had lights, a chip socket etc, that this is the first big diesel produced by Kernow with a coreless motor .

As my locos run primarily on DC I am very tempted just to put in an 0.65A hold/1.3A Trip PPTC which is the next "Littlefuse" value up - but if anyone else follows this advice they do so at their own risk especially if it is followed by a DCC chip.. Putting it in is however probably a better idea than simply shorting it out  and relying purely on the controller cutout if operating on DC. (My H&M is quite capable of powering 4 big Heljan Westerns simultaneously so it will probably deliver multiple amps to a coreless motor before tripping!)

Incidentally given the reports that the fault appears to happen on DCC with only 6 coaches trailing it also means that the DCC chips are fair chomping through the power  - i.e. the equivalent of a trailing load of 4-6 Bachmann Mark 1s !! I had not realised they were that power hungry.

 

Not quite sure what you are disagreeing with if I am honest, you seem to have explained what had been deduced above. 

 

Anyhow, the DCC failures have come with sound decoders. Plain DCC shows a current of 0.q to 0.2 amps. 

 

Roy

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2 hours ago, Roy Langridge said:

 

Not quite sure what you are disagreeing with if I am honest, you seem to have explained what had been deduced above. 

 

Anyhow, the DCC failures have come with sound decoders. Plain DCC shows a current of 0.q to 0.2 amps. 

 

Roy

Perhaps I missed it, but does anyone know the maximum permissible motor current? That seems to me to be what the polyswitch is there to limit, irrespective of whether we're suing DC, DCC sound or DCC no sound (another question: does the polyswitch respond differently to DC and DCC current?).

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