Re: Help with 7A18 problem
Colin,toggle quoted messageShow quoted text
Your suggestion should work I think but only helps when the 7A18 Input Amp itself is out of order or can't be trusted. In that case it would even be simpler to test the 7A18 stand-alone, not in a mainframe. With small signal levels, say less than 0.5 V, there will be no leakage yet via conducting semiconductors (like CR210) and no harm can be done to the FET Q210A. The only load is formed by the probe tip.
Very good that you solved the problem and explained what the problem was. With my suggested V/div check I overlooked that the cam activated contacts are not the only possible cause of troubles. I could have known better since I have had similar problems with 7A19 or 7A29. I have a dozen of 7A18/7A26 but never felt he need to look inside a switch compartment. Now I opened a 7A18N which seems easier, missing the long strip PCB over one compartment side. But in the 7A18N the compartment is completely closed. Hence it wasn't immediately clear to me that there was just one PCB inside the compartment and that this pcb has switch contacts at both sides of the PCB, in this case "left" and "right", not "top" and "bottom".
On Sun, Mar 3, 2019 at 07:53 PM, Colin Herbert wrote: