| In an attempt to quell oscillations in the (unused) outer loop portion of the ISS, I shorted the "PD+" and "PD-" signals from the (nonexistent) outer-loop diodes, and soldered in 47pf compensation capacitors in C92 and C220. This seems to have eliminated oscillations seen at TP41 and TP42. There's still something amiss at TP30 and maybe TP20. Otherwise, the ISS seems happy. I can turn the gain slider to +15dB without saturation (with the HEPA off), though there seems to be less light on the diode (~3.9V) than a week or two ago. |