Just wondering what best practice is to allow capacitors to reform when giving unused/idle amps or receivers some use after a year or two of being idle. Is it enough just to let the unit power up or is it best to actually connect speakers and play some music?
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Best practice to reform capacitors?
- Thread starter Joe Smith
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fpitas
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Wholesome reading, fresh air and exercise...ok. I've read that guys power the unit up initially with a light bulb in series, or better yet a Variac that is slowly increased to nominal line voltage.
MaxwellsEq
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If you search for dim light bulb tester, you will get some useful links such as this: https://retrorepairsandrefurbs.com/2022/06/13/building-a-dim-bulb-tester-for-vintage-radios-tvs/
In terms of load, if you've got some speakers you don't care about, you can plug them in, or you can buy dummy load resistors.
In terms of load, if you've got some speakers you don't care about, you can plug them in, or you can buy dummy load resistors.
I looked around my local stores and could not find any incandescent lamps larger than those used in ovens. Most were the LED variety. A dim bulb tester is getting harder to make as a result. Maybe I could just parallel a few of the smaller sized oven lamps to get to a 100 to150 watt equivalent.
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Here's how the DoD used to tell us: https://www.hb9aik.ch/notes/MIL-HDBK-1131C.pdf (Section 5.3).
In lieu of a light bulb, the way I used to do it was to use a series resistor to limit the current and slowly bring up the voltage with a DC power supply or Variac driving a simple unregulated transformer-based power supply. Without a variable DC supply, I tended to use a switch or decade resistor box to shunt in progressively smaller resistor values to limit the current. The fanciest I ever did was when a friend and I bought a bunch of surplus capacitors and had to reform them. We built a bunch of little op amp current sources/limiters so we could handle 16 or so at once. Mostly I used a series resistor and a DC supply, but seems like HV supplies are getting scarce these days.
In lieu of a light bulb, the way I used to do it was to use a series resistor to limit the current and slowly bring up the voltage with a DC power supply or Variac driving a simple unregulated transformer-based power supply. Without a variable DC supply, I tended to use a switch or decade resistor box to shunt in progressively smaller resistor values to limit the current. The fanciest I ever did was when a friend and I bought a bunch of surplus capacitors and had to reform them. We built a bunch of little op amp current sources/limiters so we could handle 16 or so at once. Mostly I used a series resistor and a DC supply, but seems like HV supplies are getting scarce these days.
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Some time ago I picked up a few high voltage MOSFETs from IXYS and set them up in CCS circuits. I charge a new 'lytic with constant current and watch the voltage linearly ramp up to a bit below the listed working voltage. My home brewed I-source has an adjustable voltage limiter, so I set that to prevent over-voltaging the cap. When the set point voltage is reached, the source shuts down and goes open circuit. Works well. A leaky 'lytic never makes it to the voltage limit, and that cap gets binned. Current is set depending on cap size.
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