F-UnitMad Posted September 13, 2011 Share Posted September 13, 2011 I have fitted an old Athearn (blue box) SW1500 switcher with a Digitrax SDN144PS sound decoder, with a bigger speaker (still 8 ohm like the one supplied). All going well, except that when the loco is crawling, and the horn is activated, the loco slows even more, or even stops if it was going really slow!! The loco picks up again after the horn stops. How might I overcome this? Do I need to increase the power to the motor at slow speed, maybe alter the PWM - set at 000 now, or is it the fact that I'm using the NCE Powercab which only puts out 1.5 amps or so? I wouldn't have thought it's that, though - this problem is happening when the loco is alone on the track - it can't possibly be consuming all that power?!? Any suggestions? All appreciated - thanks! Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted September 13, 2011 Share Posted September 13, 2011 There has been some discussion about this on the Digitrax Sound yahoo group. I am not sure that a solution has been suggested but i would try reducing the volume of the sounds first to see whether that reduces the problem. Then check the pick ups and wiring for any further problems with those. This seems to be a problem with the combined motor and sound decoders. After checking, it would appear that changing the speaker for a higher quality one seems to solve the problem. http://groups.yahoo.com/group/digitraxsound/message/3089 Link to post Share on other sites More sharing options...
F-UnitMad Posted September 14, 2011 Author Share Posted September 14, 2011 Thanks for that. In this case it seems to have been fitting a bigger speaker (14mm x 25mm, replacing a 13mm) that's caused the trouble!! The Ohm value is the same though. The horn volume is a bit high, so I shall have to have a play with that. There doesen't seem to be such a drop at higher speeds - or maybe not such a noticeable drop, at least - which is why I thought maybe altering the motor start voltage a bit might help. Anyway - at least it seems I'm not the only one to have this happen!! Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted September 14, 2011 Share Posted September 14, 2011 Thanks for that. In this case it seems to have been fitting a bigger speaker (14mm x 25mm, replacing a 13mm) that's caused the trouble!! The Ohm value is the same though. The horn volume is a bit high, so I shall have to have a play with that. There doesen't seem to be such a drop at higher speeds - or maybe not such a noticeable drop, at least - which is why I thought maybe altering the motor start voltage a bit might help. Anyway - at least it seems I'm not the only one to have this happen!! What ohms are you using FUnit Mad? Link to post Share on other sites More sharing options...
F-UnitMad Posted September 14, 2011 Author Share Posted September 14, 2011 The Digitrax decoder comes with a 13mm dia. 8 Ohm speaker. It (the speaker) is more intended for N scale I think, but is a bit feeble. I've replaced the speaker with a 14mm x 25mm oval 8 Ohm speaker from DCC Supplies. I've use the same decoder with an 8 Ohm 18mm x 53mm Bass Reflex speaker in a Kato SD40, and as far as I can tell, this slowing down problem hasn't occurred in that loco. Maybe it's the age of the Athearn motor & a higher current draw? (though I've no way of measuring that). Link to post Share on other sites More sharing options...
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