Has anyone fixed a Model 680 shadowgraph. I tried the usual hints from the " repair bench" with no results. the vane is free and coil shows 500 ohms resistance. #85 tube is good with 70 volts plate voltage. Thanks in advance Norman
Any chance that the bar magnet has become demagnetized?
500 ohms sounds low to me for the coil resistance - typically they're >1K.
Even if 500 ohm, still should react.
I second the magnet thought.
Just for grins take a 9v battery - to the chassis and + to the grid cap of the 85. Should cause the vane to deflect.
Thank you folks for the hints. Norman