DCC and TTS problems

[simon_parnell]

Hi all, my first post (hopefully it the right section of the forum!) :-)

Chirstmas day SOS!

Purchased brand new for today, a Flying Scotsman with DCC and TTS fitted (loco and tender only) and also a Somerset Belle DCC set with Select Controller (all Hornby).

The Somerset Belle worked fine to start with under the default assignment on the controller of 03, and also subsequently when adding assigning it tio 01.

When placing the Scotsmanpm the track (no other locos on the track) the controller displayed OL.  After removing the Scotsman from the track and resetting the controller, I then plaed it back on again.. OL again.  I attempted using a single piece of track and a simple connection for the power but everytime it trips to OL.

After this, I noticed the Somerset Belle while going round the track (oval loop with points) will at random points stop or slow completely then carry on.  I tried to see if there was a point on the track it always happened at but its really random.  Also speed and timings appear to the random too. 

I'm looking for some help to understand what I can do to trouble shoot further to work out if the enginers, controller or something else is at fault - or soemthing I'm doing?

Help please! and Happy Christmas to all! :-)

 

[Augustus Caesar]

Welcome to the forum Simon and Happy Christmas.

First things first... try ensuring the wheels are not carrying any extraeneous bits of wire that may be causing a short on points etc... unlikely as it seems.

Try reprogramming the locos. If you have a multimetre check to see if voltages are correct for the Select and that there are no drops.

Make sure all cables do have a very tight fit to the track because if one is loose then you could have either no power or 'fluctuating' which is annoying if cables are not fully connected.

 

One of our other members may have had similar issues with the Select but these are basic steps from myself.

Keep checking back as sooner or later more members will be on hand when the turkey has been finished off...

[96RAF]

The FS is obviously inducing a short which is overloading the Select. If it is th type where the tender wiring connects to the loco by way of a small white plug and socket then it could be a wiring fault ot a problem with the loco wheels and valve gear shortinh. It all depends upon the Fs type as there are many over the years.

 

If you have a multi-meter check that the loco wheels on one side have continuity with the tender wheels on the same side and vice versa.

 

Short locos can struglle across Hornby points as there is a plastic bit (frog) in the junction of the rails which causes the loco to stop or slow. Make sure the point is dead flat and watch the loco wheels as it crosses the point to see where the exact stopper os. It may ba a dodgy pickup wiper on that wheel.

[Augustus Caesar]

Trouble is there RAF is that he's getting the short on a single piece of track so it's down to the loco or Select basically.

Checking all possibilities of course is prudent.

 

As it is random and different locos to boot I suspect the Select may be at fault. If you, Simon, have a model shop which can test this for you nearby then take it along and ask if they can do you a favour and test it. Otherwise you could contact Hornby to see if they can replace it... or take it back to the shop or wherever you bought it and ask them to replace the unit.

For the track to be at fault here it is going to be very unusual in my experience unless the contacts are faulty or not making contact with the track at all times. Two locos are rarely going to be at fault together but it has probably been known so it leaves the controller.

 

Daft question but when changing the loco number you are just changing one loco at a time? All other locos must be off track unless you use a seperate track for programming (recommended).

[Chrissaf]

Any form of 'short circuit' can be problematic in a DCC layout environment. Say you have a short with loco A, but loco B is still on the track (loco B doesn't even have to be moving...it can be stationary). The short circuit that is caused by loco A can create high spike voltages on the layout that can then impact on loco B. Loco B can lose its DCC address or be affected by erroneous behaviour in other ways and in the worst case scenario have its decoder permanently damaged. Any controller displaying OL (Over-Load) is in all probability detecting a 'short circuit'.

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TIP: As this is your very first post, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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[Augustus Caesar]

Good point Chris but that assumes both locos are on the track at the same time.

The OP says he lifted one loco and reset the controller the put that loco back down although he didn't say how many were on track at that stage. He, as I stated above, had a single piece of track afterward to test the same loco and got the same fault.

In all honesty it could be any one of a few things at fault here but with one loco giving results like that it seems the loco or decoder could be the issue. However, with both locos giving problems...

I think a little more info would be helpful here as we are chasing dragons at this stage.

[simon_parnell]

 Thank you all for taking the time to review and respond, it is greatly apprecaited - after reading your reponses I can share some further info and also some multimeter results:

2 locos in question have only been placed on the track(s) one at a time.

The Somerset Belle (SB) is DCC fitted (can't find the model No)

The Flying Scotmans (FS) is DCC and FFS fitted (R3285TTS-55-355)

The SB works perfectly using an analogue controller on the same trak set up.

The FS does nothing on analogue controller and on Select will always trip to OL

Multimeter 'buzz' test on the FS, on wheels each side showed continuity between the engine and tender wheels (only the large wheels on the engine, x3 each side and all 4 on each side on the tender).

Multimeter test on the DC plug for the Select, from the mains adapter shows output is correct and stable, I think its volts, 15.25 constant.

Multimeter on the Select controler output to the track shows only 0.17 (think its volts and same setting used for the previous test on the DC plug from the mains) which then falls down as low as 0.04 and back to 0.17.  Never goes above 0.17 but never stays constant.  Not sure if this is of any actual use or relevance.

Hoping you can share some thoughts or provide more guidance.  I think the local store may be open tomorrow and I'm also going to try Hornbly but any input would be greatly received :-)

[Chrissaf]

The 15 volt DC reading on the power supply output is correct. The 0.17 volt on the Select output is probably correct if you still have the meter on the DC Voltage range (which you infer is the case in your written text). You have to put the meter on the AC Voltage range to read DCC track voltages, then you should get a reading about 14 volts give or take 1 volt..... the actual reading you get will vary with the quality specification of your meter. Most meters are calibrated to read AC voltages @ 50/60 Hz. A DCC track signal is at a nominal 7,000 Hz (cycles per second) and is a square waveform and not sinusoidal. Thus most meters will interpret the DCC signal differently.

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The FS does nothing on an analogue controller.....

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I think, if I recall correctly, that I have seen it documented that Hornby disable DC Analogue support by default on TTS decoders. If that is indeed the case, then the FS TTS should not react to a DC Analogue controller and that would be considered normal.

[simon_parnell]

 Thanks Chris - I changed the meter setting an run a few readings:

1: started at 14.6, dipped by a few volts returning to 14.6 each time ( as low as 11 if I recall)

2: started at 14.2, dipped as low as 0.01 at which point it  triggered an OL on the Select

3: started at 14.1, dipped as low as 11 but retunred toi 14.2 each time,

[Chrissaf]

Apart from the drop to 0.01 associated with the OL display, brief ad-hoc dips in the voltage is normal for DCC. You should not expect to see a rock steady consistent voltage reading. This is because you are using a voltmeter to read a waveform containing digital binary 1 and binary 0 information in it. As the data command being transmitted changes (the pattern of zeros and ones will change as well), thus the shape of the waveform changes and this will manifest itself as a change in the measured voltage. The image below is a scope display of a typical DCC waveform. DCC diagnostic measuring really needs to be done with a scope. A normal voltmeter will only give an indicative indication of DCC function with a voltage reading of about 14 volts.

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/media/tinymce_upload/f4fecf6e15a4e5a5fd9e9aad7333e6e0.jpg

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All the indications in your described text are that your FS has an intermittent 'short circuit' fault on it.

[simon_parnell]

Thanks Chris for the explanations - this makes sense and is very helpful.

Apologies for no reply but as I'm new to posting I'm only allowed x2 posts per 24 hours lol

I've been troubleshooting a bit further and think I've stumbled across something that is relevant regards the stop start issues with the Somerset Belle and have a subsequent question on the FS - I ran the SB on a simple track loop with only x2 small straights either side using the Select controller and had no issues which is pointing me towards the track setup I had tried to use previously.  That track set up has an inner and out loop made up of a straight either side and double length curves and the ends.  The loops are connected through a series of points (x6).  I've installed all the DCC clips on the points.  I'm wondering if the issue is regards signal strength/power?

I tried to put this to the test by disconnecting the inner loop and the result was the loco worked fine, no issues.

The Select controller is 1amp, do you think this is enough to power and get the signal around this amount of track?

On to the FS - this made we wonder if the power the FS needs is adequately provided by the Select?  Also, I noted the start-up numeric sequence on the Select is 15-30-03.  I did see elsewhere the current firmware version may be later as other start up sequences are 16-30-03.  I think TTS is supported on the firmware under the 15 but wondered if this could be a factor?

Really appreciate all the support and comments!

[simon_parnell]

 *update to previous post*

I noted that the power track I used was not the DCC one rather the DC obe fitted to the track set up previously.  I didn't swap this out when adding the DCC locos.

Result - Somerset Belle works fine, start/stop issues seem to be resolved.  FS, no change to tripping OL on the Select Controller.

[96RAF]

The main difference between Select v1.5 and v1.6 is the latter can change CVs and it has a new methodolgy for handling overloads and emergency stops. V1.5 can handle all TTS sound and function commands, hence the revision state should not be a factor in the problems you are having.

 

You should look carefully at the link cable as this will also have the capacitor that affects the DCC signal. you can convert your DC connectors simply by snipping out this capacitor. DCC point clips are OK for passing power to the odd siding or loop to loop but are ho substitute for the more substantial link wiring or even a power bus for total reliability when you get a permanent layout.

 

The 1-amp power supply should be able to run at least two locos if not three. I have had many TTS locos running with slipping wheels against ‘chocks’ when testing the various power supply overload trips. If the 1-amp is overloading then it will simply drop output voltage and the Select will constantly reboot. It there is a dead short then it will likely trip out. I guess your FS still has a shorting problem.

[Chrissaf]

Check each and every Hornby power clip you have used on your layout. None of them should have a suppression capacitor in them for correct DCC operation. If you have used a Hornby 'R8201 Link Cable' please note that this product is not designed for DCC and only meant to be used on DC Analogue layouts. The R8201 track clips also contain the capacitors that need to be removed for DCC to function.

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/media/tinymce_upload/780c2b9725b7af1d89fb65ce0ebaa97b.jpg

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Every capacitor across a DCC track will be shunting current through it. Thus even if there were no locos at all placed on the layout, the capacitors will each be passing about 100mA through them.

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Therefore if there are any capacitors still present there may very well be a significant current draw from your Select 1 amp power supply. Given that the FS is a bigger loco and needs more current (probably) than the S.Belle. Then the current that the FS is taking, may be enough to push the Select into 'over-load' if there are still track power clip capacitors present. Not only do the capacitors shunt DCC current across the track, they also distort the DCC waveform which can result in some decoders being unable to reliably read the DCC command data.

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The TTS decoders are particularly prone to being affected by track suppression capacitors incorrectly present across the track.

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[simon_parnell]

 Thanks Chris/RAF96,

I'm just using x1 power track and the connecting cables from the select to the power track and bare ended wires (as supplied in the SB set).  So all looks good there, thank for the pointers on the capacitors.

Called Hornby this morning, they beleive the decoder is faulty and so will need to be returned.

I've rasied a return and ordered a new model so will see what happens when that arrives tomorrow!

[simon_parnell]

The replacement FS arrived yesterday and has worked faultlessly (touch wood) so far...

The issue with the SB was down to my dcc track set up but the FS issues were due to the loco itself it seems.

Thanks to all who took time to review and reply and share thoughts to help solve my problems, really appreciate it.

Happy new year everyone!

[96RAF]

Good to hear your problem has been sorted. Happy New 2020 Modelling.