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On 16 Jun 2004 at 14:46, Mark Seaton wrote: > I will tread carefully and try to work it out. The one I have > has a copper bodied thing that looks like it might have been an ancient type > of diode, but the other one has just a wire which I don't understand as > obviously the wire would let the current flow in both directions! I guess > the diode has to go somewhere else. The copper thing is some kind of early diode; I suspect that it's just Germanium. It's actually part of the current output sensing circuit that turns things down if the generator output starts to get up to its rated 30A. They just choose something that starts to conduct at a low voltage when the voltage drop across the shunt gets high enough. They choose a low forward voltage diode to reduce the power wasted in the shunt. If you open both VRs up you will find that the later one has a small circuit board inside, which has a diode and some other stuff on it. It looks like they just went with more modern parts, probably because they could not get the germanium ones any more. The diode I add does NOT go with any of the other diodes that you've mentioned.. > Do you really think it needs to be a 3A diode? The peak current in the field is about 4A, while the 3A diode is good for an average of 3A. It's possible that you could get away with something smaller, but the price difference to me was small so I took the conservative route. -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org