[R-390] Collins R-390A, new owner

[wli]

What I did was run my fused Variac to a surplus TV
power transformer, giving me 0-400 VAC. A simple
single stage LC filter gave me 0-400VDC to check my
capacitors. By hanging a voltmeter and a milliameter
across the output, this makes a cheap, AC isolated, 
and safe utilitarian supply to check and reform R390
electrolytics. Mine is in its own grounded case with
all hot points protected (from me).

If reforming electrolytics is your goal, then this
gizmo can do it, as you monitor the current levels.
This may take hours! If all you want to do is check
gross leakage, then run the voltage up to the rated
levels and see the current passed. Throw out any
electrolytic that leaks more than 5 mA (my personal
criterion).

Hook up a 11M VTVM in series with the hot lead and an
unknown smaller capacitor, connect the grounds
together, and now you have (as was previously
mentioned by others) a megommeter. 

Any current passed by the cap will show up as a
voltage drop across the 11M input string of the VTVM.
So a voltage reading of 0.09V is a current of 1µA.
Here I reject any cap that passes more than one
microamp.

All of this was presented much more eloquently by Dr
Jerry and Roy Morgan in years past.

W. Li
Mercer Island


       
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