You might try incorporating a series capacitor into the circuit, to get rid of the stalling problem.Capacitors have a high impedance at low frequencies(speeds) and a low one at high speeds,so this could be beneficial.Because the large sizes involved you have to use electrolytic caps, these are polarized(cannot stand reverse voltages) so you have to use two back to back.My best tentative guess is to get two 1000 microfarad electrolytic caps with at least a 10V rating.Put them next to one another connect the negative leads together and wire the positive ends in series with the white lead.It would be a good idea to make it easy to short out the whole cap. combination then you can readily see what effect it has.Take pains to isolate the negative leads (the interconnection point from ground).If this cures you idle stalling problem without affecting light output unduly you're in business.If it still stalls try a series combination of one 1000 cap and one 680 cap.(for a smaller effective capacity).If the light output is too much affected try larger ones (1000/1500 ,1500/1500).The effective capacity of a series combination is: Cs= C1*C2/(C1+C2),
if C1=C2 ,Cs= C/2.The impedance is inversely proportional to capacity (impedance is esentially the ac. resistance to current flow).The impedance of a capacitor is inversely proportional to frequency (speed) or to 1/F.You will need to play around.Good luck
