pricei

I followed the guidance in the Zimo manual and tried several different P and I values in CV56 but I couldn't discern any difference in motor noise so I left it at its original value of 33. I also tried a selection of non-zero values in CV58 but that didn't appear to make any difference either. I've decided to limit my changes to CVs 9 and 57 only as per my original post. They do reduce the noise sufficiently that it can't be heard over the sound file playing which was my main concern. My thanks to everybody that offered help and advice. Ian

There might have been what looks like a capacitor on the old Heljan DC board (sorry, my knowledge of electrical components is limited) but I've dispensed with that board now and both motors are wired directly into the Zimo decoder. Ian

Thanks Norman. I did try the loco under DC before fitting the decoder and there was no groaning noise from the motors. I just tried setting CV58=0 (it was previously set to the default 255) and that did eliminate the noise but made the loco pretty uncontrollable. It needed a high throttle setting to start moving and then it was off at some speed. I guess that indicates the noise is caused by Back EMF and I'm probably going to be faced with a compromise between smooth operation and motor noise. The best I've achieved to date is changing CV9 from 95 to 25. I'm yet to try tweaking CV56 - I guess that's my best next step. Ian

The loco was in storage for a while and did have two split gears when I unboxed and checked it recently. I've since replaced all four gears (the double ones next to the worm) with brass versions from Ultrascale and the gear train now works fine. Thanks for the suggestion, though. Regards Ian

Thanks Nigel. I've already been using the Zimo large-scale decoder manual to help with the changes I've made to date. Page 23 does list a number of manufacturers/motor types but Heljan isn't one of them and I don't know whether the motors Heljan fit in their 7mm locos are normal DC or coreless. My thought was that if somebody already has a class 33/MX699 running well, their CV values would give me a better starting point from which to start tweaking.

Hi, I've just converted a Heljan class 33 (one of the first O-gauge versions) to DCC using a Zimo MX699KV decoder. The sound file is ActiveDrive SL from Digitrains. The loco works fine but there's quite a loud 'groaning' noise from the motors at low throttle settings. Having researched the issue, it seems the noise might be caused by back EMF settings? Other forum posts I've seen suggest the noise can be reduced by changing the values in CVs 9, 56 and/or 57. So far, I've changed two CV values: CV57 (original value 100) changed to 150. This was on the basis that the track voltage from my Digikeijs DR5000 varies between 16 - 18v and I assumed an average value of 17v (hence 150). CV9 (original value 95) changed to 25. This was derived by trial and error and does reduce the noise a fair bit albeit at the expense of a little more juddering at very low throttle settings. Before I try changing CV56, I was wondering if anybody else has installed an MX699KV in a Heljan 7mm Class 33 and what values they had used for CV9, 56 and 57? Regards, Ian

Thanks for the information - very useful. I was looking to control turnouts/set routes from JMRI so it's good to know that worked OK.

Hi, I'm considering a Piko SmartControl for a small, O-gauge layout. Piko's marketing material mentions the 55040 system has a 5amp output capability although from what I've read it looks like the 55040 set only ships with a 2.5amp power adapter and you need to buy a separate 55046 power supply to get 5amps (which I'll probably need for some Heljan O-gauge diesels). Can any 55040 owners confirm which power supply is included with the 55040? I'm also looking to use JMRI and would be interested in anybody's experiences of using JMRI with a Piko SmartControl. Regards, Ian