At 10/18/2007 16:23, you wrote: >At 10/18/2007 14:11, you wrote: > > >But you have a chicken and egg situation, is it the controllers fault > >or the radios? Not all radios have bias and not all controllers charge > >caps backwards. You can solve the problem by removing the mic bias > >resistor from the radio, > >I'd like to do that, but I think I just discovered a difference between the >MVP & Mastr II exciter boards: the Mastr II supplies bias via a resistor >connected to pin 11 of U101 (audio processing IC), whereas in the MVP there >is no resistor - the bias appears to provided internally within the >IC. This is a problem because there doesn't appear to be any way to remove >the bias.
I need to correct myself here: after studying the manual further, in particular the exciter board circuit description, I found that the MVP supplies mic bias from the system audio squelch board via J13. To remove it, simply unplug P13. This also removes the 620 ohm load, allowing driving the MIC HI input with somewhat higher output Z sources. Bob NO6B
