Williams wrote:
I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?



Send 'em this a way, Jimmy. Ken G just blessed me with some but I can
always use more!
-Bill M
exray at caribe.net

Williams wrote:
I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?



Send 'em this a way, Jimmy. Ken G just blessed me with some but I can
always use more!
-Bill M
exray at caribe.net

I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?

For a radio that I intend to use regularly, I follow the credo, "kill 'em
all, let God sort them out." Why would you take a chance that a decades-old
electrolytic will survive for another hour, day, or week? You can replace it
as fast as you can test it, and if you guess wrong, it may cost you an
expensive power transformer. For the price of a few lattes or a couple of
beers, you can afford to put new electrolytics in your boatanchor and sleep
soundly :-)

If you want everything to look original, you can stuff new capacitors inside
the old containers. See the article at http://antiqueradio.org/recap.htm .

Happy listening.

Phil Nelson
http://antiqueradio.org/index.html

gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil


There's some good capacitor testers around but as a rule on older BAs
(30s-40s) if it doesn't pass an ohmmeter test you need not go any
further. I chuck anything over about 1 Meg of leakage which tends to be
most all wax/paper caps from that era.
The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.
The problem is due to the breakdown of the paper dielectric inside. For
the most part thats inevitable in spite of how well sealed it is. Some
of the high-end mil-spec metal cased guys have survived but thats about
all. The rest are hit-and-miss.
In later gear, say the 50s, the "good" rate is much improved but certain
types like the banded black beauties are notoriously bad as are those
pink plastic ones found in 50s/60s Hallicrafters gear.
The debate lingers on just how much performance degradation and
reliability can be tolerated since the bad caps may not have a
particular detrimental effect *today* depending on where in the circuit
they are used. I suppose it depends whether or not you are "restoring"
or "repairing".
I cross-posted this to rec.antiques.radio+phono so you could catch some
other opinions.
Good luck!
-Bill

FWIW, 5 pages from the 1962 edition of the "Electronic Experimenter's
Handbook", starting at page 115, showed the design and construction of
"The Restorer ... gives your electrolytics a new lease on life", by
H. E. Sanders, W4CWK. It used a string of 8 NE-2's across a 720-volt
DC power supply (with dropping resistors, of course!-) to produce
selectable voltages in approximate 70-volt steps. Toward the end was
the sentence "Relatively new capacitors will form in a few minutes;
very old ones may take several hours."

A much-simpler circuit just for 450-volt caps was given in "Nuts & Volts
Magazine" in the last few years, but the page I tore and filed doesn't
have a date so I can't give a citation. But if you can cobble-up an
appropriate voltage source, it only used four additional components
(plus the capacitor to be formed); I'll try an ASCII schematic:

+------+--220K--+---NE2---+
| | | |
|+ | +--0.22C--+
450- | |
volt +---68K------------+
source 2 |
|- Cx (to be formed)
| |
+-------------------------+

Operation: "At initial power-on, the voltage across Cx is at zero and the
voltage across R2 is 450 volts, which lights NE2, the neon bulb. If Cx
is anywhere near healthy, it will slowly start to reform and charge up.
As the process continues (which can take hours), the voltage across R2
falls to the point where it is insufficient to keep the neon continuously
lit, at which time it begins to flash at a rate proportional to the amount
of current flowing through Cx. Once the neon lamp stops flashing, the
voltage across R2 is too low to light the lamp, and it can be assumed Cx
is fully charged and successfully reformed. For lower-voltage electro-
lytics, adjust the [source] voltage [to match the working voltage of Cx]."

--Myron, W0PBV.

--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

FWIW, 5 pages from the 1962 edition of the "Electronic Experimenter's
Handbook", starting at page 115, showed the design and construction of
"The Restorer ... gives your electrolytics a new lease on life", by
H. E. Sanders, W4CWK. It used a string of 8 NE-2's across a 720-volt
DC power supply (with dropping resistors, of course!-) to produce
selectable voltages in approximate 70-volt steps. Toward the end was
the sentence "Relatively new capacitors will form in a few minutes;
very old ones may take several hours."

A much-simpler circuit just for 450-volt caps was given in "Nuts & Volts
Magazine" in the last few years, but the page I tore and filed doesn't
have a date so I can't give a citation. But if you can cobble-up an
appropriate voltage source, it only used four additional components
(plus the capacitor to be formed); I'll try an ASCII schematic:

+------+--220K--+---NE2---+
| | | |
|+ | +--0.22C--+
450- | |
volt +---68K------------+
source 2 |
|- Cx (to be formed)
| |
+-------------------------+

Operation: "At initial power-on, the voltage across Cx is at zero and the
voltage across R2 is 450 volts, which lights NE2, the neon bulb. If Cx
is anywhere near healthy, it will slowly start to reform and charge up.
As the process continues (which can take hours), the voltage across R2
falls to the point where it is insufficient to keep the neon continuously
lit, at which time it begins to flash at a rate proportional to the amount
of current flowing through Cx. Once the neon lamp stops flashing, the
voltage across R2 is too low to light the lamp, and it can be assumed Cx
is fully charged and successfully reformed. For lower-voltage electro-
lytics, adjust the [source] voltage [to match the working voltage of Cx]."

--Myron, W0PBV.

--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

put some DC thru it. If you get DC current thru a capacitor it may be
defective. Measure with a suitable ampmeter and resistor.(ohm meter
check) Capacitors look leaky when checked using AC. :^

gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil

put some DC thru it. If you get DC current thru a capacitor it may be
defective. Measure with a suitable ampmeter and resistor.(ohm meter
check) Capacitors look leaky when checked using AC. :^

gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil