"Chuck Harris" wrote in message
...

That would be fine if you are looking to get doused with electrolyte.
A better test would be to measure the capacitance as they sit.
Then reform them with a 1.5K resistor in series with the supply.
Then retake the measurements.


No dousing and no noticable heat, either. I did ESR and capacitance
checks with the old caps as they came out of the drawer, at 15V for 24
hours, at 25V at 24 hours, and 30V at 24 hours. I had to use a
different power supply to get 30V. The Heathkit checker takes a large
step from 25V to 50V. I didn't want to deal with limiting the checker's
voltage.


If the cap isn't drawing current during the reform, it means the
maker got the electrolyte formulation right, you probably won't see
much change in measured characteristics. If the cap is drawing
heavy current during the reform, you should see greater differences
in the reformed cap vs the "NOS" cap. ESR should go down, capacitance
should go down, and so should leakage current.

-Chuck, WA3UQV


I think we can both say with confidence that Ducati got the electrolyte
formulation right, way back two or three decades ago. I didn't measure
any significant change in capacitance or ESR (except ESR went up on a
couple on the last test). If they had a +/- 20% tolerance, they were in
spec at the start and stayed in spec at every step of the test. But I
never noticed a big change when I've checked electrolytics before.

Here's the numbers from the cap tests. The format is cap number, ESR
in ohms, capacitance in ufd.

Column 1, out of the drawer after sitting unused for maybe 25 years.

Coulmn 2, after 24 hours with 15V applied.

Column 3, after 24 hours with 25V applied.

Column 4, after 24 hours with 30V applied.

1 .19, 100 .18, 105 .19, 100 .20, 105
2 .22, 100 .20, 100 .22, 100 .22, 105
3 .21, 105 .20, 100 .22, 105 .23, 103
4 .20, 110 .19, 105 .21, 110 .30, 108
5 .21, 115 .20, 105 .22, 115 .33, 110
6 .21, 109 .20, 102 .22, 100 .24, 110
7 .24, 103 .22, 098 .25, 100 .25, 110
8 .23, 098 .21, 098 .24, 098 .23, 100
9 .16, 112 .16, 112 .18, 112 .20, 115
10 .21, 100 .20, 100 .22, 100 .20, 115
11 .22, 099 .21, 098 .23, 098 .23, 105

There might be a couple of trends. Both capacitance and ESR went up on
a few. I can't make much of that because of possible measurement
errors. There are no gross changes off the shelf and with voltage
applied.

These old caps tested with pretty good precision. The newer ones test
in even tighter groups.

Frank Dresser