I had a 5061A that had those symptoms. It had been running in Cs off mode for a long time and the Ion Pump current looked like zero on casual inspection but was actually barely perceptibly just off the zero mark. I took that to mean that the ion pump had kept the vacuum in the tube very well. The fault turned out to be no voltage at pin 4 of the 3500V supply A18 due to failure of the internal 100 Meg resistor. That resistor forms part of a voltage divider from the +3500 that provides a "+3500 supply good" signal to the rest of the system.
If you can't find a replacement A18 you can repair it but it's a bit of a job. You need to unsolder the base from the case and then the layout is obvious. There's a soldered-over cap on the bottom of the unit that I assume covers a hole used to fill it with nitrogen or some other inert gas. Good luck! Morris > Is there any hope. I would believe so. CS tubes are pretty tough. As Scott > says HV supplies but you measured those and they appear good as you say. So > its a knock down drag out battle. You have nothing to loose so dig in. > I wonder if the SRD may have popped. But its funny the ion pump is 0. That > seems a bit odd. always a bit of crud in the tube that should make that >kick up. My 10 cents. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
