[GreenKeys] [External] New Member Says Hello

[Jones, Douglas W]

From: Robert Abeles [phil99boyd at gmail.com] -- Friday, August 11, 2023 3:58 PM

> The first step on my restoration journey will be to check the electrolytics. It's been sitting unused for 20+ years,

I've had pretty good luck reforming ancient electrolytics (one big exception).  Just get a variable DC power supply and crank up the voltage very slowly, keeping the current at a few times the leakage you'd expect for that size capacitor.  Keep going until the voltage is 20% over the rated voltage and the current is close to a leakage current you'd expect.

I tended to use a series resistor and monitor the current by measuring the voltage across that resistor.  I rarely raised the voltage more than one or two volts, as little as once a day, and as frequently as hourly.

With a teletype, the power supplies are trivial enough that you can just hook the whole thing (with the motor disconnected) to a variac and slowly crank up the voltage to the AC power cord.  You can't do this with machines that have switching power supplies.

        Doug Jones
        jones at cs.uiowa.edu