Capacitor stuffing

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One of the first steps to a proper vintage tube radio restoration is replacement of old capacitors. Typically the wax/paper and the electrolytic are "Shot-gunned" or wholesale replaced prior to any other troubleshooting or further restoration. The old capacitors can be clipped out and new ones installed. Or Re-stuffed.

Re-stuffing a capacitor is the process of putting new internal components into the original capacitor shell. Most typically this is done to the electrolytic can capacitors that are mounted to the top side of the chassis. Most times the electrolytic capacitors are simply disconnected and abandoned in place. New capacitors are installed under side of the chassis, out of site.

The original wax/paper capacitors may also be re-stuffed for a "Museum" quality restoration. This is a very time consuming process usually reserved for the most precious of radios. Most Wax/paper capacitors will never be seen unless the chassis is removed from the cabinet and flipped over.

When there is no space under the chassis for new electrolytic capacitors the original can may be "re-stuffed" with the new replacement capacitors. These pictures below of a Zenith Transoceanic electrolytic capacitor showing the steps on how it is done.

On Chassis - Twist Lock can capacitor restuffing.

This location in a Zenith Transoceanic is too cramped for additional capacitors. And this radio is very sensitive to component placement near the wire coils (bottom left tube).	Heating the black cardboard with a 40 watt lamp softens the black tar holding the cover on the can. *No need for an expensive heat gun or a damaged hair dryer and an upset wife.*	After even heating the cover it pulls free with little force. Be careful not to break the can to chassis insulator.
The Dial cord and tuning pulleys have been removed to afford access. **Plenty of tape and protection from hack saw hits and saw dust has been added. A contaminated variable air tuning capacitor can be difficult to clean.**	A hack saw blade with out the handle is used with a light touch. Sawing too hard risks cracking the capacitor to chassis insulator.	The capacitor has been cut through, exposing the plates and paper. This cap is quite dry. Electrolytic capacitors typically have liquid electrolyte to enhance their capacity.
Clean out the remains. Next, drill additional small holes for capacitor lead access.	Two of the caps have been labeled with the square and triangle symbol representing the multi-section can values. The new caps are hot melt glued in place for when the chassis is flipped and the lead wires soldered.	The speaker was un-bolted and swung clear to cut the right side can cap. Next the black cardboard covers were returned and secured with a small amount of hot melt glue around the base of the can. A small amount was used to allow future service access.
A Twist Lock Can capacitor on the bench.
Remove capacitor by carefully unsoldering the wires and untwisting the locking tabs. Heat and remove cardboard cover and cut the can open.	Remove and discard old dried contents. Clip the lead wires, from the foil plate, level with the base.	Drill additional access holes in the can base to accommodate the new capacitor lead wires. Install and hot melt glue in the new capacitors. Solder the lead wires to the original solder lugs.
Re-assemble using hot melt glue. Reinstall the can and gently twist the locking tabs being careful not to snap them off.	Re-stuffing a can capacitor saves space and maintains the original vintage look above and below the chassis.

Stud can capacitors. (not restuffed)

Here is detail of a Philco capacitor. The internal plates have been removed with a long needle nosed pliers. The post was reinstalled with epoxy to be used as a binding post. This makes a convenient place to solder an external capacitor.

Re-stuffing a capacitor is debatable when the conditions of; A) There is plenty of room under chassis and B) The other replacement capacitors have not been hidden (re-stuffed) with in the original wax/paper capacitor wrapper.

Cut the stud out and remove internal plate. Cut off the original insulator. This one measured low resistance (for an insulator) on a DVM (about 2 meg). At full B+ there would be current flow and eventual dielectric breakdown. There is absolutely no need to take such risk (carbon trail, short circuit) when simple fixes are available.	This is great Epoxy purchased at Home Depot. It hardens in minutes (like a rock) and has a spec for insulating capability!
A salvaged terminal has been soldered to the stud to replace the original solder tab.	Stud replaced using Epoxy and a bit of heat shrink tubing. This capacitor was reinstalled a Philco 40-150. It is in the middle of the chassis with two red wires and a black electrolytic connected to it.

On the chassis - Can capacitor replacement (not restuffed).

A terminal strip is used to mount the new capacitors and provide a convenient place to hook up wires.

In the chassis can capacitor modification. Step 1. Remove center pin with pliers and insulator while can cap is in chassis. Step 2. Straighten the mounting tab on a terminal strip. Step 3. Push mounting tab in capacitor opening. Step 4. Mix up some Oatey plumber's epoxy and push into the hole. When the epoxy is hard connect up the wires and add new electrolytic capacitor.
	This is how the whole chassis looks with unstuffed can caps. This is the restored chassis. Most of the wires were brittle and some were bare. All paper/wax and electrolytic capacitors have been replace.

1923 Grebe Syncrophase bypass condenser (capacitor).

Careful heating on a low setting releases the wax.

B+ Bypass condenser measures 3.8 uf.

These caps are replaced. I would not want 90 or 135 volts on the old paper insulators. The replacement is 450v. A terminal strip is used for mechanical strength,

C+ bypass condenser about 3 uf (original). This replacement is 160 v. A much lower voltage would have done fine. These were abundantly in stock.

A little hot melt glue will adequately seal up these capacitors. The tin exterior not shown is receiving a sprits of gloss black and a shellac top coat. I will save the original internals in case an owner would like a 1920's cap.

"Silver Mica Capacitor Disease" in the IF transformer.

If you hear a rushing or thunder storm coming from you speaker regardless of what band or frequency you tune to. The volume typically quiets the noise when you turn the volume down. Follow this hyperlink.

Don't forget the Bakelite blocks.		Click here for How To.
And how about those Dog gone Dog Bone Resistors?		Try Syl's web site.
Do you want to Restuff the Waxed Paper capacitors?		See this link to start.

Another link for caps http://oldradio.ca:83/Radio/CapRestuff/restuff.html

Safety capacitors

There are particular capacitors that are connected from the chassis to one or both of the power lines (mains). These capacitors are typically called RF bypass capacitors. They shunt signals that would interfere with the proper operation of the radio. They also provide an RF ground point for the antenna system of the radio.

See Just Radios for the ABC's of Safety Capacitors.

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On Chassis - Twist Lock can capacitor restuffing.

A Twist Lock Can capacitor on the bench.

Stud can capacitors. (not restuffed)

On the chassis - Can capacitor replacement (not restuffed).

In the chassis can capacitor modification.

This is how the whole chassis looks with unstuffed can caps.

1923 Grebe Syncrophase bypass condenser (capacitor).

"Silver Mica Capacitor Disease" in the IF transformer.

If you hear a rushing or thunder storm coming from you speaker regardless of what band or frequency you tune to. The volume typically quiets the noise when you turn the volume down. Follow this hyperlink.

Don't forget the Bakelite blocks.

And how about those Dog gone Dog Bone Resistors?

Do you want to Restuff the Waxed Paper capacitors?

Safety capacitors