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