18-08-2012, 06:04 PM
Thanks, Lawrence.
As I said in the original post, my version has two parallel-connected 1000µH inductors - one mounted vertically and one horizontally to avoid mutual inductance. There was only 0.3Ω difference in the DC resistances of these so they seemed OK.
I found that connecting my DMM where the 'scope had been had the same effect and then discovered that connecting a 47pF capacitor there, ie between the highlighted rail and ground, seemed to fix it nicely.
I was puzzled that it had worked initially. I can only think that as it was on an 18" long board there was enough stray capacitance kicking about.
I've spent so long today looking at it that I've given myself back-ache so I'll have a better idea of what's what tomorrow and I can also get on and case it up.
Cheers
Joe
As I said in the original post, my version has two parallel-connected 1000µH inductors - one mounted vertically and one horizontally to avoid mutual inductance. There was only 0.3Ω difference in the DC resistances of these so they seemed OK.
I found that connecting my DMM where the 'scope had been had the same effect and then discovered that connecting a 47pF capacitor there, ie between the highlighted rail and ground, seemed to fix it nicely.
I was puzzled that it had worked initially. I can only think that as it was on an 18" long board there was enough stray capacitance kicking about.
I've spent so long today looking at it that I've given myself back-ache so I'll have a better idea of what's what tomorrow and I can also get on and case it up.
Cheers
Joe
