ksoholm
Senior member
- Location
- Bellingham, WA, USA
Mates,
I recently had the RGS's tach fettled by Wolfgang - new chip - but the needle still waved around. I posed the question on the FB Lav World page, and a gent named Dick B?thker responded that the Witt filter should be installed with black and brown wires swapped, black to ignition, brown to earth. He says the filter is designed as a low pass filter, but that the tach needs a high pass filter as there is much DC on the line. Connected like this, it becomes a high pass filter, getting rid of much of the DC. He said: ?The tach seems sensitive to the average voltage. That is high at low rpm and drops at higher rpm. It should not be sensitive, but it is. The solution is to remove the DC component, which is what a high pass filter does. Original configuration is low pass which does not help: it keeps the DC.? The good Herr B?thker by accounts is a big-time Laverda man, and seems to know his stuff.
I swapped leads as required today, and can report a dead-stable needle, problem cured. So, all these years the filter wiring recommendation may have been incorrect.
Best,
Kristian
I recently had the RGS's tach fettled by Wolfgang - new chip - but the needle still waved around. I posed the question on the FB Lav World page, and a gent named Dick B?thker responded that the Witt filter should be installed with black and brown wires swapped, black to ignition, brown to earth. He says the filter is designed as a low pass filter, but that the tach needs a high pass filter as there is much DC on the line. Connected like this, it becomes a high pass filter, getting rid of much of the DC. He said: ?The tach seems sensitive to the average voltage. That is high at low rpm and drops at higher rpm. It should not be sensitive, but it is. The solution is to remove the DC component, which is what a high pass filter does. Original configuration is low pass which does not help: it keeps the DC.? The good Herr B?thker by accounts is a big-time Laverda man, and seems to know his stuff.
I swapped leads as required today, and can report a dead-stable needle, problem cured. So, all these years the filter wiring recommendation may have been incorrect.
Best,
Kristian
