Reply To: Will these Capacitors Work?

[Tom]

The dV/dt value on the capacitor in question here is something like 1200, if I recall from when I looked it up yesterday. That should be fine. I believe the MKP1839…HQ series is somewhere around 1000. I’m sure there are other specifications that apply, but since you have them on hand, give them a shot on a hot day and report back.

Regarding a capacitor tester, the Heathkit IT series tester cited above is an excellent way to go if you can afford one. They are quite expensive when compared to the lesser Heathkit C-2 or C-3. I’ve rebuilt several C-2 units and they are more than adequate for my purposes. They test up to something like 400V and can also be used to measure resistance and capacitance with better than 10% accuracy if capped correctly. Even the C-2 and C-3 units consistently go for $75 to $100 on the bay, although one slipped by for less than $40 last weekend.

As mentioned in a previous post: “As an aside, I recently went through a bin of condensers that had been saved by a friend. There were over 50 condensers. I tested them at 200 V with a Heathkit C-2. There were two good ones in the pile. One was a new OMC, the other was an original condenser from a Johnson A.”

One final note: I’ve never found a used brass can WICO condenser that was useable. Even after removing the internals to use the can as a housing, the leakage across the “insulator” at the top could cripple a rebuild. So if you’re rebuilding any of those, measure the leakage of the empty can before you stuff new guts in it. I’ve had success doing this with the Vishay capacitor after learning that I had to test the empty can. (These are the stand up condensers with the screw terminal on top and the tab about halfway down for mounting it upright. In many Scotts and Martins, replacement with a standard configuration condenser is difficult.)

Tom