10000 Posted January 15, 2011 Share Posted January 15, 2011 As a novice with DCC I'm hoping someone can help. I fitted a decoder to a Hornby Class 31 and it appears to be drawing to much amperage. Hope the following makes things clearer. DC operation it runs fine, lights on and no sign of problems. DCC system is an NCE Powercab with a CP6 circuit protector. For those not familiar with this it splits the track feed in to 6 sections each protected by a bulb and limiting the max amps for each section to 1. Fitted a TCS T1A and set long address to 5511. Transfered to main track. Started it running and as I increased its speed the bulb for that section started to brighten suggesting a short was developing or too many amps been pulled. As I slowed it down the bulb dimmed. Max speed was not as high as on DC Took the decoder out and checked the amps on DC system they never exceeded 0.4 amp. The decoder is now in a Heljan 26 and everything is fine. Fitted a Lenz Silver+. Again programmed long address to 5511 and the problem reoccurred exactly the same with this decoder. So have I a faulty loco or is it CV values that need adjusting. Thanks in advance Mike Link to post Share on other sites More sharing options...
Brian Posted January 15, 2011 Share Posted January 15, 2011 Hi The NCE PowerCab has the ability to be able to read current demand on the handset. Suggest you test this loco and via the PowerCab check its normal running current load. If its near to, just on or greater than 1.0Amp then that's the problem. You could also check there is nothing binding anywhere on the loco? A dc running current and stall current test prior to fitting the decoder would also tell you how much current demand the loco will have. See my web sites DCC pages for hope to do this test. Link to post Share on other sites More sharing options...
amdaley Posted January 15, 2011 Share Posted January 15, 2011 To access the ammeter in the Power cab do the following. Press Prog/Esc 6 times or Prog/Esc then 6. Set cab Params shows. Press Enter. TRK Current 1=Y shows. Press 1. The ammeter should now show in the top right hand corner instead of the clock. If the loco is new it may have a tight spot somewhere.I suggest that you run it in on DC first. 30minutes each way on medium power should do it. Do not race it around the track under full power.Check it for slow running. If it has a tight spot it may show under slow running.Listen for any squeaks or rubbing sounds. Link to post Share on other sites More sharing options...
10000 Posted January 15, 2011 Author Share Posted January 15, 2011 Thanks for the rapid replies. Like all my loco's irrespective of brand it was run in for 1 hour in each direction at a moderate speed with no load behind. Speed control at low speed on a Gaugemaster is similar to most modern diesel models. There is no tightness or sticking. I previously checked the amps on DC with no load at various speeds As I said it never exceeded 0.4amp. Stall test I haven't done but the first Decoder used the TCS is a 1.3 continuous 2 amp max and the CP6 limits to 1amp add to which it was not stalled it increased speed and as it increased the lamp came on. The Lenz is still in, the body is off so no lights involved. Max speed on DCC is about 1/3 of max on DC and the amps peaked at 0.82amp more than double that it achieved on DC, and it was running not stalled. I can program CV's on it which if it was shorting the Powercab would not do. Mike Link to post Share on other sites More sharing options...
smokebox Posted January 15, 2011 Share Posted January 15, 2011 Check for faulty connections on the DCC socket. It's possible to have a short circuit between two pins that doesn't show up when a blanking plug is fitted for dc running but WILL cause excess current to be drawn when a decoder is fitted. Link to post Share on other sites More sharing options...
Brian Posted January 15, 2011 Share Posted January 15, 2011 Hi again If your locos motor demands 0.4Amp (400miliamp) on dc then it will require the same on DCC (give or take a few milliamps) The increased current reading indicates a fault somewhere. Do as suggested and check that there is no contact underneath the plug when its fully inserted into the socket - Assuming it has a plug in a socket and its not hard wired? If you can't see anything under the socket, it may be worth levering up the plug a little and sliding a strip of PVC insulating tape under the socket. Then gently push the plug back home. If its hard wired, then recheck with the aid of a multimeter that the motor terminals are fully insulated from the chassis after removing the Grey and Orange wires from the motor. You could also try replacing the decoder with a known working one and retry, as it is possible there is a fault within the actual decoder itself? Finally ensure the actual decoder PCB isn't touching anything or the wiring isn't being trapped and partially cut through by the body or other components. Link to post Share on other sites More sharing options...
10000 Posted January 16, 2011 Author Share Posted January 16, 2011 Thanks for the suggestions. It is an 8 pin plug so I shall check it and the circuit board. I will post my findings as soon as I can Mike Link to post Share on other sites More sharing options...
10000 Posted January 16, 2011 Author Share Posted January 16, 2011 Progress so far The socket is an integral part of the circuit board, not one soldered in, solid bottoms to it so the decoder pins cannot poke through. Checked the socket with a multimeter. The only sockets that showed continuity was 1 and I assume 8 - the motor feeds. Disconnecting a motor wire from the board cleared that. Visible exam also reveled nothing. Released the board from the chassis so it had no contact with anything metal, still got the problem. Disconnected all wires for lights from the board leaving only the pickup wires from each bogie and the motor feeds. Problem still there. Disconnected the red motor wire from the board. Of course it didn't run and was drawing no amps at all. Unfortunately I do not have another loco with a similar circuit board to swap over. The 2 decoders (1 TCS and 1 Lenz) both work fine in other locos's I have not removed the 'cap' because getting to it meant removing the circuit board (OK I could remove it now I have the board loose) . Link to post Share on other sites More sharing options...
amdaley Posted January 16, 2011 Share Posted January 16, 2011 Progress so far The socket is an integral part of the circuit board, not one soldered in, solid bottoms to it so the decoder pins cannot poke through. Checked the socket with a multimeter. The only sockets that showed continuity was 1 and I assume 8 - the motor feeds. Disconnecting a motor wire from the board cleared that. Visible exam also reveled nothing. Released the board from the chassis so it had no contact with anything metal, still got the problem. Disconnected all wires for lights from the board leaving only the pickup wires from each bogie and the motor feeds. Problem still there. Disconnected the red motor wire from the board. Of course it didn't run and was drawing no amps at all. Unfortunately I do not have another loco with a similar circuit board to swap over. The 2 decoders (1 TCS and 1 Lenz) both work fine in other locos's I have not removed the 'cap' because getting to it meant removing the circuit board (OK I could remove it now I have the board loose) . Check the underneath of the circuit board. It has been known that during manufacture that excess solder around on of the pins could be touching an adjoining pin. Link to post Share on other sites More sharing options...
10000 Posted January 17, 2011 Author Share Posted January 17, 2011 Tony, the circuit board is surface mounted components, so no solder on the underside. As I'm getting no where I'm going to put it aside for now. Next time I get some decoders I will include a wires only one (I do have a use for it anyway) and try removing the circuit board completely and wire direct to the motor. At least then I should find out if it is the circuit board or the motor. Thanks everyone for the help Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted January 17, 2011 Share Posted January 17, 2011 It's the circuit board - well, pound to penny anyway - based on my experience. I have an example where the loco ran fine on DC test using a simple resistance controller. But once decoder fitted it was very sluggish. Off with board, hardwired decoder directly between pick ups and motor, and performance was immediately transformed and remains excellent. Nothing 'scientific' about the decision to remove the board, just that it had about four times the necessary component count for a start, and removing it left a nice big void to place the decoder in.. Link to post Share on other sites More sharing options...
10000 Posted January 17, 2011 Author Share Posted January 17, 2011 OK 34etc, Thank's for that. It sounds just like mine so thats the route I'll take next time I order some decoders (probably end of feb now, just paid a big gas bill). Did you wire the lights as well. I have heard that Hornby used a +ve common and that decoders need a -ve common Mike Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted January 17, 2011 Share Posted January 17, 2011 Didn't bother with the lights as the chassis was receiving an Airfix body. Link to post Share on other sites More sharing options...
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