Capacitor Rebuilding or How to satisfy the purists... :)

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Capacitor Rebuilding or How to satisfy the purists... :)

Postby unixslave » December 8th, 2011, 7:22 pm

Sometimes a hack, does not necessarily involve bleeding edge tech.

Sometimes, it's the nitty gritty work that pays the bills to allow us to play...


When ever we are working in an old set, TV, Audio Amplifier, or Turntable, invariably we will
run across capacitors of all types, Paper, mica, electrolytic, etc....

Generally when we run into caps that are of the electrolytic type they are mostly dry, or drying out.

Some common practices have technicians just shotgunning the problem by swapping the offenders out
with current technology caps.

Electrically equivalent.....but to some of my audiophile customers, it is blasphemy bordering on the obscene.
I maximize my bottom line with these individuals by keeping them happy with the older look of the parts.

It should also be noted... with times being what they are... You can command a little bit more for the
units you choose to sell on ebay or whatever when no current technology parts are visible.

Hence the title of this thread.


Let's start off with the offending part.

A dual cap 50uf@150wvdc in a waxen pressed board container.

Black is common, Red and Orange are the + leads.


Nicely, notice I did not use the word gently... :)
Take an old soldering iron and use it to liquefy the resin and waxen plug in the end of the cap.

Some liquid will co-operate and gently flow out, the rest will become soft like putty, and easily
manageable with the tip of a small flat screwdriver. NOW, gentle heating with a HAIR DRYER will
loosen the material near the wall, and then clean it with the screwdriver.

When you get to them, cut the cap leads at the rivets. (You will see them and feel them with the
melting iron)

When you get deep enough, take soldering iron and press it into the center of the old cap material.
This will make a pilot hole.


Take a 3/8th's drill and while holding the cap shell by the side, measure (with the drill bit) how
deep you can go, less about 3/4" just for safety, and mark it with some tape
Now, take the cap and hold it with gloves or whatever you feel comfortable with... and gently
drill into the cap materials.

If you go slowly, the drill SHOULD take a grab onto the whole core when it gets into the upper resin
and the whole core SHOULD spin in the cap barrel. STOP drilling when you get to the tape mark or
the core spins.


Now grab the core with a hooked dental pick, o-ring tool, or even a small bit of wire with a
slight hook in it. Pull out your prize.


Here are your 5 constituent parts of the cap, less the plug material.


Now, here comes the fun part.
Take the replacement value caps, for ME, alone, I used three 25uf@250v caps per side of the cap.
Remember, CAPS IN PARALLEL ARE ADDITIVE, while keeping the working voltages the same.
Yes, I purposely chose 3 caps because they will form a triangular pattern for better centering.

I put a large loop on these negatives, since this will be the common point for the cap.


Cap bundle with the positives wired and the rest is now the pigtail for one of the positive leads.


Needed to be done twice. Leave enough wire on the second bundle to hook them together.


Take the negative lead from the second cap, and feed it through the center of the first cap,
and cut it long enough to hook it to the first bundle's loop(remember that?)


Remove the second cap bundle. Take some black tape and put a layer or two on the top of
the first bundle. Poke a hole in it with the tip of a soldering iron.


Reassemble the two cap bundles, soldering the negative lead from the second bundle, and
the black(or whatever color it is) to the lug on the first bundle.

Attach the remaining original wires to the positive leads.


Now, insert the whole new stack 'o caps into the old shell. Take a moment to admire your work.

(no pics of the next 2 steps)

Cut out a small piece of gray cardboard . The annoying fiberboard most things are shipped in or
used as card material. Cut it down to the size of the inside of the cap shell.

Poke 3 small holes for the leads. Feed the leads through the holes and press the fiber circle into the
cap body, pushing it in about 1/2".

Take your melting iron, and using a small candle(unlit) preferably white, but not a brilliant white,
melt the bottom of the candle filling in the bottom of the cap body. This is simply for aesthetics,
but what the heck. Don't be lazy and burn the candle to drip. There is conductive carbon in
the dripped wax.


Tahdah! A brand new 'antique' cap. Take a second moment to chuckle.


Re-inserted into the chassis. Smile knowingly to yourself.
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Joined: December 8th, 2011, 7:18 pm

Re: Capacitor Rebuilding or How to satisfy the purists... :)

Postby error404 » December 8th, 2011, 10:21 pm

Nice technique, but pretty damn unethical to sell them as if they were 'vintage' parts, regardless of their electrical equivalence.
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Joined: January 28th, 2011, 3:04 am

Re: Capacitor Rebuilding or How to satisfy the purists... :)

Postby sraasch » December 9th, 2011, 7:38 am

It would be unethical to sell this as ORIGINAL, but the technique is commonly used in the tube-radio community. These radios will likely fail (destroying components that are unobtainable) unless the radio is "re-capped".
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Joined: December 9th, 2011, 7:35 am

Re: Capacitor Rebuilding or How to satisfy the purists... :)

Postby gearbox » December 9th, 2011, 5:54 pm

Are you at all concerned when dealing with those old capacitors about PCBs? (
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Joined: December 9th, 2011, 5:47 pm

Re: Capacitor Rebuilding or How to satisfy the purists... :)

Postby Arrangemonk » December 10th, 2011, 10:31 am

Audiophiles are Idiots.
like people who buy a 3000€ hdmi cable and pretend to see the difference.
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