RMweb Gold Tony_S Posted July 3, 2014 RMweb Gold Share Posted July 3, 2014 I mentioned on the Heljan Garratt thread that my loco has gone back to Hattons today. Their returns system seems very efficient and their telephone staff very helpful. What I'm curious to know is what could possibly cause the fault. Over the years I've had a few dead on arrival decoders and have damaged a couple myself but his was strange, so I'll describe the symptoms. Following advice from another RMweb member I purchased a Lenz Standard + 8 pin decoder for the loco. For those not familiar with the model it has one decoder and two motors. It also has lamps on either end. So I install the decoder, and initially just set it to a four digit number using my Sprog. All seems well. Under low speed testing it trundles nicely and so it goes to the main layout (Lenz DCC system). At half speed it just stops and the handset throttle has to be set to minimum before the loco moves again. It also seems slow to respond to light on/off commands. Other locos are happily working at the same time. There was one occurrence of a high speed runaway. I returned the loco to the SPROG system and tried turning off DC as I recall that sometimes was allegedly responsible for runaways. No change. I had a fiddle with some of the other parameters and no change. I could recreate the fault using a Decoder Pro throttle with the Sprog system so it wasn't the Lenz DCC set. I reset the decoder. No change. I tried another Lenz Standard + decoder. Exactly the same. I was still thinking it was a decoder issue and installed another make (one of Hattons own that actually appears to be a DCC concepts decoder. Exactly the same, fine up to half speed then dead. So, I've eliminated decoders, DCC system, all that is left is the loco which has enabled decoders to program. If I'd purchased a loco second hand at a bargain price I would probably have rewired it to eliminate the circuit board but what I would be interested in is what kind of wiring or component fault could create these symptoms! Tony Link to post Share on other sites More sharing options...
RMweb Gold Oldddudders Posted July 3, 2014 RMweb Gold Share Posted July 3, 2014 Is there any chance that the unsynchronised BEMF from two motors is confusing the decoder? In that case it should affect them all, of course, and that obviously isn't true. Link to post Share on other sites More sharing options...
Simon G Posted July 4, 2014 Share Posted July 4, 2014 A friend of mine has (had!) a Heljan Garratt, that has also been returned. It was DCC installed, and ran extremely poorly. The final straw was when the Emergency Stop on the controller was pressed and the loco continued to run for a while, then stopped and went into reverse! Another one was test run on our Club Layout and constantly derailed in one direction. From all that I have heard, this long awaited model is turning out to be a bit of a disaster! Link to post Share on other sites More sharing options...
Edwin_m Posted July 4, 2014 Share Posted July 4, 2014 Is there any chance that the unsynchronised BEMF from two motors is confusing the decoder? In that case it should affect them all, of course, and that obviously isn't true. Could it be a "random" effect which only happens when the two motors happen to be running out of (or even in) synchronization. Link to post Share on other sites More sharing options...
Adrian Wintle Posted July 4, 2014 Share Posted July 4, 2014 Are you possibly hitting the current limit of the Lenz decoder and causing it to shut down? Adrian Link to post Share on other sites More sharing options...
shortliner Posted July 4, 2014 Share Posted July 4, 2014 This is probably silly, but is it possible that it needs two decoders, one for each motor, that then need to be "consisted" as though it were two locos (each with a seperate motor) running coupled together? Just a silly passing thought Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 4, 2014 Author RMweb Gold Share Posted July 4, 2014 No it has two motors, one decoder. On both varieties of decoder I experimented with turning BEMF off. Other RMwebbers have used the Lenz decoder successfully on the LMS versions of the loco. I don't think the Hatton's decoder I also tried has the same characteristics (short protection etc) as the Lenz but the behaviour was the same. I'm hoping mine was some fault on the loco's pcb causing the fault. Tony Link to post Share on other sites More sharing options...
RMweb Gold beast66606 Posted July 4, 2014 RMweb Gold Share Posted July 4, 2014 This is probably silly, but is it possible that it needs two decoders, one for each motor, that then need to be "consisted" as though it were two locos (each with a seperate motor) running coupled together? Just a silly passing thought It's Ok to run two motors with one decoder provided the total current draw is within the limits - if using two, it's easier to give them the same address, no need for consists then. No it has two motors, one decoder. On both varieties of decoder I experimented with turning BEMF off. Other RMwebbers have used the Lenz decoder successfully on the LMS versions of the loco. I don't think the Hatton's decoder I also tried has the same characteristics (short protection etc) as the Lenz but the behaviour was the same. I'm hoping mine was some fault on the loco's pcb causing the fault. Tony Tony, Can you temporarily by-pass the circuit board ? Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 4, 2014 Author RMweb Gold Share Posted July 4, 2014 It's Ok to run two motors with one decoder provided the total current draw is within the limits - if using two, it's easier to give them the same address, no need for consists then. Tony, Can you temporarily by-pass the circuit board ? On a more simple loco I would have ripped out the board and hard wired it but this one has so many looms and plugs I thought I would see what the nice people at Hatton's said first. There appear to be some capacitor type lumps on the board and a couple of resistor shaped items (that may be inductors). The diodes for the headlamps on DC are on the decoder blanking plate. If I had bought it used on eBay I would probably had it in bits by now but Hattons are very good about problems. I did successfully put a decoder in a Bachmann class 24 today just to prove I can do something practical! Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 4, 2014 Author RMweb Gold Share Posted July 4, 2014 I must admit programming it via the Lenz handset wasn't something I tried but a loco I programmed this morning with the Sprog was fine. Like Dutch Master suggests it may well turn out to be an unfortunate coincidence of causes. It was just a bit perplexing, I'm usually reasonably good at problem solving. I really don't think I did anything stupid but if I did I shall confess! Link to post Share on other sites More sharing options...
Crosland Posted July 4, 2014 Share Posted July 4, 2014 The programming might make a difference, but not the programmer used to achieve it. The SPROG, especially, will not do anything underhanded that you do not specify via the DecoderPro GUI. Andrew Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 7, 2014 Author RMweb Gold Share Posted July 7, 2014 I received an email from Hattons confirming dispatch of a replacement Garratt. I'll report back when I fit a decoder in that one! Tony Link to post Share on other sites More sharing options...
Sunnysa Posted July 8, 2014 Share Posted July 8, 2014 I know nothing of Len standard decoders or Heljan Garratt but owing to Heljan locos are notorious for high current draw is it possible that, if 2 motors are involved, the current draw is exceeding the limits of Lenz decoder. Cheers Ian Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 8, 2014 Author RMweb Gold Share Posted July 8, 2014 I know nothing of Len standard decoders or Heljan Garratt but owing to Heljan locos are notorious for high current draw is it possible that, if 2 motors are involved, the current draw is exceeding the limits of Lenz decoder. Cheers Ian Other people have had no problems with that Lenz decoder in the Garratt and there was no evidence of an overload event. In addition it exhibited the same behaviour with a Hattons decoder. Tony Link to post Share on other sites More sharing options...
Phil S Posted July 8, 2014 Share Posted July 8, 2014 You don't mention WHICH Hattons decoder - but the ones I have been getting are only rated about 1 Amp .... and I wouldn't expect to run 2 Heljan motors off 1 of them! Has anyone actually measured the dc current taken by their Garrett before deciding on which decoder to fit? .. and the stall current .... which could be 'unusually high' as it is 2 motors which are statonary to start with. Then, when running; to achieve the same speed, a 'lower' dcc voltage will require a proportionally larger current than a 'higher' dcc voltage .... so if you are restricting your dcc track voltage to 12V (as some people apparently do [ many being N gaugers matching some '9V' models ... but not all!] you will be running your decoder(s) nearere their current limit. Running at say 16Vdcc track voltage will give approximately a 12V drive to the motor ... and 3/4 of the current. As the decoders use pulse-width-drive, avoiding the 'linear region' it is more efficient to drive them at the higher voltage, with 'thinner pulses' as they produce less heat, fo the same track speed. Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 8, 2014 Author RMweb Gold Share Posted July 8, 2014 It was the Hattons small red sleeve decoder. I wouldn't have used it as first choice in the Garratt either but after two Lenz Standard+ decoders had demonstrated odd behaviour the only other 8 pin decoder I had handy was one of the Hattons ones. It exhibited identical behaviour. None of the decoders I tried even seemed warm. Hopefully the new one will be fine, it is currently out for delivery by Yodel! Edit. Silly me, the package from Hattons via Yodel was some coaches. The Garratt will arrive tomorrow via Royal Mail. Tony Link to post Share on other sites More sharing options...
Phil S Posted July 9, 2014 Share Posted July 9, 2014 Given that modern decoders have inbuilt overload protection - ie they switch themselves off rather than fry - the problem mat still be too low a rating - and the decoders cutting out to protect themselves before you fry the eggs anf bacon in the firebox. Hav eyou measured the stall current of the garrettt yet? Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted July 9, 2014 RMweb Gold Share Posted July 9, 2014 The characteristics of the Lenz Standard+ decoders are 1A continuous, 1.8A max and > 5A stall. Given that most OO gauge motors these days draw less than 0.5A, I would not think this loco should overload the decoder. Most likely cause is a mechanical issue that's causing the mechanism to get stuck. I have a Bachmann standard 4MT loco that exhibited the same problem and it too has a Lenz Standard+ decoder. I'd taken it off the track to clean it, and hadn't noticed when I replaced it that the centre driving wheels had slipped between the rails. So as soon as power was applied the mechanism essentially locked up. No lasting damage - just re-rail the centre drivers and all OK (and go to Specsavers next time). Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted July 9, 2014 Author RMweb Gold Share Posted July 9, 2014 The original loco went back. It wasn't a mechanical fault as when it ran away on the Lenz system it certainly moved! I was able to get down and view the mechanism and everything seemed perfect either forward or reverse up the half speed when it stopped. The replacement arrived this morning, I removed the DCC access cover, removed the 8 pin blanking piece, inserted a TCS T1, programmed a new number and tried it in the short track connected to the Sprog programmer. Fine, no problems. I took it down to the layout and it works perfectly. Very happy. I forgot to fit the coupling so it hasn't pulled any wagons yet but it pushed some nicely in reverse. Tony Link to post Share on other sites More sharing options...
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