Hornby Elite over voltage

[john-1208839]

Hi I've just purchased the hornby elite and installed a DCC decoder into the flying scotsman with an ringfield motor then plugged in the programing track and successfully gave it a new address 2 then changed the leads over to the track side to test the train i changed the loco to address 2 tested that the train was working forwaed and reverse everything was good. I then changed over to the programing track again to install another flying scotsman witch was a DCC ready train with the installed R8106 tts sound decoder this was programmed to address 1 then moved back to the track and tested the train everything was working as it should including all the sounds. i then switched everything off came back to it the next day put the old flying scotsman on the main track switched everything on but as soon as the elite fired up i got an error message on the screen so i lifted the train of the track reset the error switched of the elite put the train back on the track switched on the elite same thing again so i took the train back off then tested the voltage going to the track from the elite its at 18.5 volts AC im thinking thats not right as it says it should be 15volts AC on the output i've also tested the supplied power supply its 15.2 volts DC does anyone know if i'm missing something here or any advice on what to check next. Thanks

[Rog RJ]

18.5 volts could be perfectly OK, depends on the quality of the meter you are using.

DCC isn't a normal sinusoidal alternating voltage, it's a sort of an irregular square wave at a frequency of about 8Khz. This is difficult to measure accurately with many multi meters, some will give a low reading and some will read high.

I wouldn't worry about the voltage you are seeing.

The short circuit could be caused by a faulty suppression capacitor on the motor. You can cut it off, it's not needed on DCC, or if it's brand new return it for repair, replacement or refund.

[Chrissaf]

I totally agree with what Rog is saying about the meter. Any reading a meter reads on a DCC track is just an indication that track voltage is present. Cheap meters are calibrated to read a pure sine wave typically at about 1Khz. DCC is a nominal 8Khz square wave with a variable mark / space ratio. You need special meters to accurately measure DCC voltages.

The alternative measurement you have already documented as being taken is to take a reading on the output of the 15 Volts DC power pack. If a 15 volt DC input is going into the Elite, then unless ringing is taking place on the DCC output, it is not likely that the actual DCC voltage on the output is exceeding 15 volts. If the power pack output is 18 volts due to a power pack regulation fault, then yes the DCC output could feasibly be correspondingly higher than the nominal 15 volts.

I mentioned ringing above. It is technically possible for the DCC signal on the track to be unstable and exhibiting oscillation. This is termed 'ringing'. Ringing can generate peak to peak voltages up to 50 or 60 volts or sometimes more and these can indeed damage decoders. The only really definite way to know if your DCC is ringing, is to look at the track signal with an Oscilloscope.

A ringing DCC waveform will then look something like this:

The yellow highlights show the ringing voltages. In this example creating peak to peak voltages of 58.8v [highlighted upper right].

Ringing can be dampened by adding a simple filter across your DCC track, termed a 'snubber'.

The snubber filter is made from two cheap simple components. A 100 Ω [Ohm] resistor rated at 1 watt power rating [2 watts preferred as it will get very hot to the touch] in series with a 0.1µF [micro-Farad] Ceramic capacitor rated at 50 volts or above. Both components can be fitted either way round as they are not polarity sensitive.

Even if your DCC track voltage is not 'ringing', installing a 'snubber' is still a worthwhile decoder protection measure to take, as brief ringing is very typical when a transient 'short circuit' occurs. Loco running into a misrouted point for example.

[ColinB]

I suspect it is not your Elite, I don't know which decoder you are using but if you are using a Hornby one for a Ringfield motor powered loco then probably you have damaged it. Ringfield motors are on the current limit for a Hornby decoder and quite a number of others as well. So sometimes they work ok but then if the motor draws slightly more then they seem to fail. Hattons do the same. I have a second hand Elite I got off EBay. I must admit other than the rotary control settings it is incredibly reliable. If you have a 5 pole Ringfield motor they seem to draw less current, but the early 3 pole ones can draw up to 0.8 amp. I use Zimo decoders which are a little bit more expensive at £20.00 compared with about £16.00 but they are rated at about 0.8 amps and so far have no issues driving older locos.

[96RAF]

You don’t say which loco is causing the error, but I would be closely inspecting the decoder socket as there have been cases reported of solder tracking between the pin track. If it is the ring-field one then look at what Colin said, but also check you have converted the ring-field correctly to isolate the motor brushes from the pickups.

To measure the square wave form of DCC accurately you need an RRAMP meter which can be quite expensive for casual use.

This shows the output from my Elite on an RRAMP meter.

A normal multimeter set to AC volts will read a value but it is as Roger says it is reading the sinusoidal (mains) waveform not square. Accuracy will vary according to the sampling rate of your meter. Check you meter spec versus the DCC frequency Roger quotes.

[john-1208839]

Hi Guys and thanks for all the info after reading i'm thinking i've blown the chip in the ringfield motor on the old flying scotsman that was the one i put down on the track first just in case,the newer flying scotsman was the DCC ready train so it was just a case of fitting the TTS sound chip Rog i took the capacitor of the old ringfield motor before fitting the DCC chip im thinking ill go with Chrissaf and fit the snubber to the track but will i need to fit just one or will i need to put one at every dropper point and would i be safe to put one on the program track as well, and the meter im using is a precision Gold PG-017 from maplin not an expensive one but did the job. so i've a few more tests to do and i've got a class 55 to get DCC fitted so once that's done ill test the track again and see how things go ill let use know thanks

[96RAF]

Three things.

1. you need to be sure you have converted the ring-field motor correctly. There must be no continuity between either motor brush and the wheels/pickups, which may be half loco - half tender or if diesel half front bogie - half back bogie.
2. You only fit a snubber on the open ends of a bus, not everywhere.
3. You do not fit anything extra on a programming track else it will corrupt the programming signal and prevent access to changing the decoder.

[Chrissaf]

Snubbers.

Definitely not on the 'programming track. The 'programming track' does not have enough power [current] on it to support a snubber, and to fit one will prevent the 'programming track' from working correctly.

You only need one on the main DCC track and definitely not one on each dropper. Snubbers will shunt about 100mA of current, which is why they get very hot to touch. The more 'snubbers' you add ... would increase the current drawn from your controller to the point where there would be no current left to run trains. One single snubber will protect the whole of an average domestic sized layout. If the DCC power is distributed as a T BUS, then two snubbers [one each end of the T], but no more than two.

For the correct way to DCC convert a Ringfield motor you need to measure the 'stall current' on DC first to ascertain the required current specification of the decoder. Then you also have to identify what type of Ringfield you have [there are three different basic types each with their own conversion requirement].

These links will assist with these tasks:

Brian Lambert's 'Stall Test' guide

Brian Lambert's Decoder Install Page [scroll down for Ringfield]

[ColinB]

So how is the RRamp meter different to say the RMS measured on a Fluke multimeter? I Googled it but basically all I can find is that it measures AC. I am pretty sure the Fluke gets the current wrong for DCC as when I measure stall currents with DC and do the same with DCC (on a separate piece of track) the value is lower, so I am wondering if the RRamp has a different algorithm.

[96RAF]

See here Colin

https://s3-us-west-2.amazonaws.com/mrhpub.com/2019-09-sep/online/index.html?page=65

and also this extract copied from RMWeb

To measure DCC voltages accurately I believe that you need to use a RRampmeter, or a multimeter specifically designed to read DCC voltages, but that can be expensive, and on ESU's forum some folks report good results using a simple, and cheap, rectification circuit, as shown below (courtesy of K Rainer) connected to the multimeter set to measure DC voltages. 



The voltmeter will under-read by 1.4 volts because of the voltage loss caused by the bridge rectifier.

[ColinB]

Thank you 96RAF for the link, it still doesn't tell me that much more but I will just assume it gets it right. My multimeter is a reasonably expensive Fluke, but I am pretty sure although it says it measures true RMS, I think it assumes it is sinusoidal AC.

[Chrissaf]

A high quality 'True RMS' meter takes 100's if not 1,000's of samples of a waveform and then runs those samples through a sophisticated mathematical algorithm. The whole idea of the concept of a 'True RMS' meter is that it is designed to measure waveforms that are not sinusoidal**. Hence the 'sampling rate', the more expensive the 'True RMS' meter is, the higher the number of samples taken. By taking a high number of sample readings, the meter can deduce the waveform shape and then apply an appropriate algorithm to calculate the measured value. My understanding is that the RRAMP meter, is basically a 'True RMS' meter with a very high sampling rate using an 'algorithm' designed specifically for DCC waveforms.

Note** of course, the 'True RMS' meter will still measure 'sinusoidal' waveforms as well, but with a very high degree of accuracy.

Just as an aside, most meters are typically calibrated to measure 50/60Hz [sine-wave] with about a 1Khz bandwidth, which is absolutely fine for the average user. If one wants to pay the extra for a higher quality meter, then look at the specs and when comparing price, compare the 'Bandwidth' specification. Higher the quoted bandwidth spec then the higher the meter quality.

[Flashbang]

I was given as a retirement gift a Fluke 187 True reading RMS multimeter, which has as I understand has a sampling rate of up to 10KHz and it measures DCC voltage correctly on its AC range. I also have a lower quality Fluke 87 which on DCC is not quite as accurate but nearly so.

I addition have three 'cheap' "Chinese" True RMS multimeters and none of those measure DCC rail volts correctly!

Unfortunately, my Fluke 187 has now an internal defect and I contacted Fluke UK last year to ask about a repair? "No repairs available for a meter that old" (its about 14 years old!) . But we can offer you a new version replacement for 50% off the list price as a swap.. Cost £360 plus VAT! Fluke UK said. I politely declined and left that one on their shelves.

[john-1208839]

Hi and thanks for all the info sorry for delay in posting reply I've had issues with broadband and talktalk but all sorted now. so I've ordered the parts for the snubber to be connected at one end. And I've converted the class 55 diesel to DCC yesterday and tested it on the track everything working but its a bit jittery on start up I'm guessing I need to adjust the start-up voltage for this, I've also braved putting the new flying scotsman on the track and all ok including the sounds so i guess I've fried the chip on the old flying scotsmam somehow but you live and learn. wish there was a big dummies guide on converting from DC to DCC time to go read some manuals.

 

[Mac-_-]

Wish there was a big dummies guide on converting from DC to DCC time to go read some manuals.

 

 

We're all dummies when it comes to things we know nothing about ;). As for DCC it's like everything in life, it can be as hard or as easy as you make it (one step at a time solves most things). Though there is people out there that try to make it sound complicated.

[ColinB]

Unfortunately with DCC it is so easy to blow decoders up. It is usually because assuming you wire it up correctly, when you try and squeeze it into the available space some stray wire touches the chassis. The other issue with older locos is they draw more current than new ones, so you fit the decoder test it on a length of tack, but when you try it on your layout with points and curves the motor has more load and suddenly you smell the telltale sight that another one has died. I killed loads when I first started, fortunately of late that has stopped. Hornby will replace a TTS decoder if damaged and under one year old, even if you accidentally damaged it.

[john-1208839]

Hi Yes its a new learning curve for us here in the shed its my grandson who is running the trains and I'm the maintenance provider and the layout is not to big its L shaped with 3 curves and a siding with 6 tracks on it it was all running great on DC but after we got a leak in the shed roof we decided to go to DCC. But i didn't know how much work was involved its all just about done with the exception of the points we had all insulfrog points on the layout so I've just put point clips in them for now they do seem to be working ok, But I've been checking the forum and its suggested to change them to electro frog points so will get this done when money allows.

And start up voltage was something that wasn't considered on DC either so I'm trying to find the best start up volts for the 3 old ringfield motor trains I've converted to DCC they do all run but very jittery on start-up and sometimes have to give them a gentle nudge as well.

And thanks for all the comments very helpful information i must say I've learned a lot since joining the forum. Now where's my elite manual.

[Chrissaf]

As your layout was previously a DC Analogue one and upgraded to Digital DCC. Then if you are still using any of the Hornby R8206 and R602 power connection products, then these will need to be modified for DCC working. The capacitors inside these analogue power components distort and corrupt the DCC signals and can create very strange behaviours to be observed. How to modify the track power connectors to remove these capacitors is shown below:

[john-1208839]

Hi Chrissaf

No I'm not using any of the analogue connections they were all removed and I've ran bus wires under the layout and have put in at the moment 7 droppers in the oval part of the track and I'm thinking of putting another 4 in the siding as well once I've got the track to finish the siding. The droppers are the ones attached to the rail joiners but was thinking of putting the wire onto the outside edge of the track lots of stuff to try till i get it right.

i have also started cleaning all the loco wheels and give the ringfeild motors a service then going to double check the rail joiners for a tight fit as i have noticed that some of the trains are slowing down when going over certain parts of the track so hopefully this will help as well, could you recommend a supplier for led lights as I'm just getting my supplies from Hornby at the moment. I'm going to put leds in the class 55 diesel and if i can get the hst to run leds for that as well many thanks.

[Chrissaf]

Individual LED components

Bright Components

LED lighting kits for locomotives.

Welcome to Express Models the home of models railways

[Fishmanoz]

Hi John, I’m sitting in Sydney on a lovely warm sunny Good Friday. The sun is most appreciated as we are told it is to be bookended by a week of rain either end, the previous end being somewhat excessive as a 100 year flood event.

Anyway, your shed troubles brought a smile to my face due to a long-remembered quote from a much esteemed gentleman from your side of the world, although I doubt he would identify with my description. I needed the smile as what some people have posted recently has been having the opposite effect (think JJ not wanting to stop or scratch his maglite coach taking it apart (read what he said) or Chris redoing his dry joint soldering again (knowing Chris, he’ll fix it the first time)).

But the quote - “there’s a hole in the roof where the rain gets in. The hole is small, that’s why the rain is thin,”.

I trust I have no need to attribute that quote, otherwise so soon we forget him.

I can also assure you that even thin rain will be just as devastating to DCC as it was to DC, if not more so.

[96RAF]

If you are using the slide in power clips you can check them for a capacitor or not without opening them. See the yellow block.