I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

Mark wrote:
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

You have three choices:

1. Bring the things up slowly, on a variac. This allows the capacitors
to slowly reform.

2. Bring the things up for a while with a 60W light bulb in series, then
apply full power. Same basic principle, if you don't have a variac, but
slower.

3. Apply full power. If any caps blow, they were marginal and should have
been replaced anyway.

I tend to be a fan of method #3, but I can understand the arguments in favor
of the first two. But caps that are only a decade old? Don't sweat it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Mark wrote:
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

You have three choices:

1. Bring the things up slowly, on a variac. This allows the capacitors
to slowly reform.

2. Bring the things up for a while with a 60W light bulb in series, then
apply full power. Same basic principle, if you don't have a variac, but
slower.

3. Apply full power. If any caps blow, they were marginal and should have
been replaced anyway.

I tend to be a fan of method #3, but I can understand the arguments in favor
of the first two. But caps that are only a decade old? Don't sweat it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
Mark wrote:
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

You have three choices:

1. Bring the things up slowly, on a variac. This allows the capacitors
to slowly reform.

2. Bring the things up for a while with a 60W light bulb in series, then
apply full power. Same basic principle, if you don't have a variac,
but
slower.

3. Apply full power. If any caps blow, they were marginal and should have
been replaced anyway.

I tend to be a fan of method #3, but I can understand the arguments in
favor
of the first two. But caps that are only a decade old? Don't sweat it.
--scott



Many manufacturers of aluminum electrolytic caps recommend they be reformed
after 18 months of storage, others say 2 years, and others say 3 years.

"Scott Dorsey" wrote in message
...
Mark wrote:
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

You have three choices:

1. Bring the things up slowly, on a variac. This allows the capacitors
to slowly reform.

2. Bring the things up for a while with a 60W light bulb in series, then
apply full power. Same basic principle, if you don't have a variac,
but
slower.

3. Apply full power. If any caps blow, they were marginal and should have
been replaced anyway.

I tend to be a fan of method #3, but I can understand the arguments in
favor
of the first two. But caps that are only a decade old? Don't sweat it.
--scott



Many manufacturers of aluminum electrolytic caps recommend they be reformed
after 18 months of storage, others say 2 years, and others say 3 years.

Much has been written and published on the net on this topic but just
to add my two cents and perhaps summarize. I've had good luck with a
variable HV DC supply. I bring up the voltage, albeit slowly, while
monitoring current with a microamp meter. It's nice to watch the
current gradually go lower, then I step up about another 50 volts or
so then watch it go lower again until I reach the rated voltage of the
cap. I let it "Cook" there for awhile then use the cap. There's a
formula for the "Cook Time" based on the age of the cap. Do a net
search for that one. Someone in G land I think. I have restored and
recapped a lot of older HF radios this way and it has saved me a
tremendous amount of cash.The new Electrolytics are a lot
smaller/better but we're talking about five bucks each here. I wait
till they show up at the Flea Market or local surplus outlet then
scoop em up for .25 each. Oooops! Maybe I shouldn't have told you
about that.


Tony WA6LZH







(Mark) wrote in message . com...
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

Much has been written and published on the net on this topic but just
to add my two cents and perhaps summarize. I've had good luck with a
variable HV DC supply. I bring up the voltage, albeit slowly, while
monitoring current with a microamp meter. It's nice to watch the
current gradually go lower, then I step up about another 50 volts or
so then watch it go lower again until I reach the rated voltage of the
cap. I let it "Cook" there for awhile then use the cap. There's a
formula for the "Cook Time" based on the age of the cap. Do a net
search for that one. Someone in G land I think. I have restored and
recapped a lot of older HF radios this way and it has saved me a
tremendous amount of cash.The new Electrolytics are a lot
smaller/better but we're talking about five bucks each here. I wait
till they show up at the Flea Market or local surplus outlet then
scoop em up for .25 each. Oooops! Maybe I shouldn't have told you
about that.


Tony WA6LZH







(Mark) wrote in message . com...
I have obtained some surplus linear regulated power supplies. The
date code for the electrolytic caps in the filter section are late
1993. I've not powered these
supplies up. I know that these caps have a limited life. These caps
are also
harder to come by due to the proliferation of switch mode power
supplies and
their lower values. Any ideas/suggestions to minimize stress to these
caps
or even rejuvinate, if possible, these caps. I'm aware of inrush
current at
supply turn on and I plan to minimize that. Any other ideas or
suggestions???

I've had good luck with a
variable HV DC supply. I bring up the voltage, albeit slowly, while
monitoring current with a microamp meter. It's nice to watch the
current gradually go lower, then I step up about another 50 volts or
so then watch it go lower again until I reach the rated voltage of the
cap. I let it "Cook" there for awhile then use the cap.

Tony & Mark-

I consider ten-year-old electrolytics to still be "new", and of a newer
generation than those that established a reputation for going bad when first
powered-up after being in storage. Its those thirty and forty-year-old
capacitors I worry about!

I have an old Eico capacitor checker with the "electric eye" indicator for
leakage. The voltage is also somewhat current limited. Years ago when I was
working with it, I would connect an old electrolytic to it and raise the
voltage until the eye just closed. Depending on capacitance and leakage, the
eye would slowly open. I would then continue raising voltage and waiting for
the eye to open, until the rated voltage was reached, typically 450 volts.

This is equivalent to forming a capacitor by using the variac or series light
bulb. I never worried about cooking it, since there was obviously no leakage
soon after full voltage was reached. I think you will find those that still
have leakage after several minutes, are beyond help. (Obviously ten mfd will
charge a thousand times more quickly than 10,000 mfd.)

I think I'll go reform the capacitors in my capacitor checker!

73, Fred, K4DII

I've had good luck with a
variable HV DC supply. I bring up the voltage, albeit slowly, while
monitoring current with a microamp meter. It's nice to watch the
current gradually go lower, then I step up about another 50 volts or
so then watch it go lower again until I reach the rated voltage of the
cap. I let it "Cook" there for awhile then use the cap.

Tony & Mark-

I consider ten-year-old electrolytics to still be "new", and of a newer
generation than those that established a reputation for going bad when first
powered-up after being in storage. Its those thirty and forty-year-old
capacitors I worry about!

I have an old Eico capacitor checker with the "electric eye" indicator for
leakage. The voltage is also somewhat current limited. Years ago when I was
working with it, I would connect an old electrolytic to it and raise the
voltage until the eye just closed. Depending on capacitance and leakage, the
eye would slowly open. I would then continue raising voltage and waiting for
the eye to open, until the rated voltage was reached, typically 450 volts.

This is equivalent to forming a capacitor by using the variac or series light
bulb. I never worried about cooking it, since there was obviously no leakage
soon after full voltage was reached. I think you will find those that still
have leakage after several minutes, are beyond help. (Obviously ten mfd will
charge a thousand times more quickly than 10,000 mfd.)

I think I'll go reform the capacitors in my capacitor checker!

73, Fred, K4DII