On Sat, Aug 26, 2017 at 5:57 PM, Rob Jarratt via cctalk <cctalk@classiccmp.org> wrote: > > I have replaced several parts in the area of the monitor sense circuit, > including the comparator and the buffer it is driving, but the comparator > does not seem to be doing what you would expect. I have reverse engineered > the circuit and I simply don't understand how the circuit can behave in the > way it is behaving. I have posted all the details here: > https://rjarratt.wordpress.com/2017/08/26/decstation-220-monitor-sense-circu > it-problem/ > > Does anyone have any ideas what could be going on?
My first worry is that you have measured the reference voltage as 0.36V, but according to your schematic, said point has only a resistor to +5V and a capacitor to ground. So I would expect it to be close to 5V. -tony
