Rebuilding Electrolytic Capacitors
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ferninando
Lunatic Member
do you mean "restuffing"? Putting new caps in old cans?
kvflyer
Super Member
Yes.
Though not every step shown completely, look at post #53 here.
The screw was used as a pull handle to remove the innards after heating the can with a heat gun. Remember to wear thick gloves to handle the hot can.
Also, 3 of the metal lock tabs (which also served as common negative to chassis) had broken off trying to get the can out of the chassis. So, I drilled a center hole for the common negative leads as seen in the pics in post #54. If they hadn't broken, I would have drilled side holes and soldered them to the locking tabs, but I didn't want to chance that last tab as being my only ground if it would break on reintallation. Post #57 shows restuffing the crossover caps in the console.
Other steps not shown as they seemed self explanatory with the photos:
Hacksawing the can (you can see registry marks for realigning the can parts.
Extending the leads of the "upper" caps with 600V 22ga wire, heatshrink to insulate
Applying the JB Weld and then "clamping" (I used tape to hold the pieces together)
Grinding the excess JB Weld after it cured with a Dremel tool
Wrapping and soldering the leads to the correct posts
Buffing the can with a Scotchbright pad.
The screw was used as a pull handle to remove the innards after heating the can with a heat gun. Remember to wear thick gloves to handle the hot can.
Also, 3 of the metal lock tabs (which also served as common negative to chassis) had broken off trying to get the can out of the chassis. So, I drilled a center hole for the common negative leads as seen in the pics in post #54. If they hadn't broken, I would have drilled side holes and soldered them to the locking tabs, but I didn't want to chance that last tab as being my only ground if it would break on reintallation. Post #57 shows restuffing the crossover caps in the console.
Other steps not shown as they seemed self explanatory with the photos:
Hacksawing the can (you can see registry marks for realigning the can parts.
Extending the leads of the "upper" caps with 600V 22ga wire, heatshrink to insulate
Applying the JB Weld and then "clamping" (I used tape to hold the pieces together)
Grinding the excess JB Weld after it cured with a Dremel tool
Wrapping and soldering the leads to the correct posts
Buffing the can with a Scotchbright pad.
I really need to do this with a couple of wet caps on an old EH Scott I have. Problem is, I need to rebuild the insulators since they are currently rubber, and in horrible shape. I'm thinking plastic washers and rubber grommets, along with a brass screw for the terminal. I've had that thing sitting around almost a year now, so its time to do something with it. Its too awesome to be a dust collector.
kvflyer
Super Member
I have some work pending on the Grand Cherokee. It seems that again, a squirrel has bitten holes into the Nylon fuel line. A year ago, he bit a hole downstream of the fuel filter. I fixed that and now, new holes are in front of the fuel filter! Car is out of commission so I need to address that... Darn.
What I need to do is to take some pictures of closing the can and the way that I do the final crimp. No big thing, I just want continuity. I have it all written up with pictures etc. Just need a couple more pictures.
Again, Thanks for waiting...
What I need to do is to take some pictures of closing the can and the way that I do the final crimp. No big thing, I just want continuity. I have it all written up with pictures etc. Just need a couple more pictures.
Again, Thanks for waiting...
kvflyer
Super Member
Rebuilding Electrolytic Capacitors *Pictures Now!*
Several members have asked about rebuilding electrolytic capacitors. What I prefer to work on is HH Scott amplifiers. I just like the way that they are built and sound. I also have excellent results with a restoration or for that matter, just to get one going. As you all know, the electrolytic capacitors are rather old, between 40 and 50 years old. The capacitors were never designed to last that long. However, some still survive. I will not be a hypocrite and tell you that every amplifier, tuner or receiver that I own have new electrolytic caps. They do not. But I carefully monitor the operation of them by sound (ears!) and feel (touch). They should never get warm unless heated by radiated heat from the tubes.
What I want to show you is my approach to this issue. This is not the only way or the best way to go. It is the way that I have chosen to go because of pride in the accomplishment and frugality. I can rebuild a can for less than $10 and frankly, it is fun. Please realize that these pictures are not all of the same capacitor. I have done several caps and this is a compilation of photos. But you get the idea.
First is the un-crimping of the aluminum can lip. This is dangerous and requires much care if you choose use this method. Always point the blade away from you; never hold the cap in your hand. I start by getting the blade under the crimped aluminum and working it gently up.
I continue to raise the lip with the small screwdriver. (For those of you who worked for the Bell System, this was referred to as a dial screwdriver
).
After I get enough of the aluminum pried up, I use a pair of duck billed pliers to straighten the aluminum slightly. This allows the steel ring and "guts" to come out more easily.
Next, we heat the outside of the can with a heat gun. Mine is a paint stripper gun but you could borrow your partner's hair dryer. Just remember to put it back where you found it or you will hear about it. (Look closely in the background and you may see an adult bevy. Obviously, this picture was taken in the evening!)
Next, we see the insides of the can pulled out. Sometimes this is easy, sometimes it is a bear. I use welder's gloves to hold the heated can and pull the guts out carefully. You don't want to pull the lug out of the fiber disc.
Here are the new electrolytic capacitors that will be inside of the can. They are much smaller and after searching the vendors' website, I found what I needed. (Those 500 WVDC caps are still elusive though)
After I have the components mounted on the phenolic wafer and soldered to the lugs, I start by rolling the edge that I had pried up on the face of my cast iron vice. I roll back and forth and eventually most of the aluminum folds back over the wafer.
After it is rolled as much as possible, I use a small light weight tack hammer to work my way around the edge carefully. I do this slowly because the aluminum is stretched and wants to bunch up. If I am patient, it smooths back down after going around the edge a couple of times.
The parts:
And the finished product. You have to look closely to see the wires. I use either a #60 drill or 1/16" depending on lead size.
Several members have asked about rebuilding electrolytic capacitors. What I prefer to work on is HH Scott amplifiers. I just like the way that they are built and sound. I also have excellent results with a restoration or for that matter, just to get one going. As you all know, the electrolytic capacitors are rather old, between 40 and 50 years old. The capacitors were never designed to last that long. However, some still survive. I will not be a hypocrite and tell you that every amplifier, tuner or receiver that I own have new electrolytic caps. They do not. But I carefully monitor the operation of them by sound (ears!) and feel (touch). They should never get warm unless heated by radiated heat from the tubes.
What I want to show you is my approach to this issue. This is not the only way or the best way to go. It is the way that I have chosen to go because of pride in the accomplishment and frugality. I can rebuild a can for less than $10 and frankly, it is fun. Please realize that these pictures are not all of the same capacitor. I have done several caps and this is a compilation of photos. But you get the idea.
First is the un-crimping of the aluminum can lip. This is dangerous and requires much care if you choose use this method. Always point the blade away from you; never hold the cap in your hand. I start by getting the blade under the crimped aluminum and working it gently up.
I continue to raise the lip with the small screwdriver. (For those of you who worked for the Bell System, this was referred to as a dial screwdriver
).
After I get enough of the aluminum pried up, I use a pair of duck billed pliers to straighten the aluminum slightly. This allows the steel ring and "guts" to come out more easily.
Next, we heat the outside of the can with a heat gun. Mine is a paint stripper gun but you could borrow your partner's hair dryer. Just remember to put it back where you found it or you will hear about it. (Look closely in the background and you may see an adult bevy. Obviously, this picture was taken in the evening!)
Next, we see the insides of the can pulled out. Sometimes this is easy, sometimes it is a bear. I use welder's gloves to hold the heated can and pull the guts out carefully. You don't want to pull the lug out of the fiber disc.
Here are the new electrolytic capacitors that will be inside of the can. They are much smaller and after searching the vendors' website, I found what I needed. (Those 500 WVDC caps are still elusive though)
After I have the components mounted on the phenolic wafer and soldered to the lugs, I start by rolling the edge that I had pried up on the face of my cast iron vice. I roll back and forth and eventually most of the aluminum folds back over the wafer.
After it is rolled as much as possible, I use a small light weight tack hammer to work my way around the edge carefully. I do this slowly because the aluminum is stretched and wants to bunch up. If I am patient, it smooths back down after going around the edge a couple of times.
The parts:
And the finished product. You have to look closely to see the wires. I use either a #60 drill or 1/16" depending on lead size.
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kvflyer
Super Member
Please remember that this is not the ONLY way to rebuild capacitors. But it is kinda fun and I enjoy doing it. What is a pain is when they have gobs and gobs of components soldered to the lugs. I take many, many pictures and still diagram how and where everything went. If not, disaster!
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kvflyer
Super Member
Thanks for the comments. The first attempt that one makes can be intimidating especially if you HAVE to use the capacitor being operated on. I might suggest some practice runs just to get a feel of it. Open up some cans from an old TV or whatever and go from there. In the first few that I did, I cleaned every bit of the potting compound out of the can. I used lacquer thinner and an old toothbrush. But later, I realize that it really doesn't matter. I get the most of it out and make sure it is washed out to get the old electrolyte out and then start reassembly.
Another thing is to be patient when closing up the can. Alan Douglas uses an old burnishing tool, kinda like a round piece of metal with a handle that is ground down to a point kinda like an ice pick about as big around as your little finger and starts rolling/pushing it down around the circumference. Since my vice is bolted to the bench and is a huge cast iron hunk, I just carefully start to roll the edge back around as much as I can. Then I use that tack hammer because it has a long head and isn't very heavy. Carefully working your way around the edge does work. Sometimes, I have to slightly hammer the outside edge to make the stepped portion go back into place. But the key is to do it slowly and gently. You want to work the aluminum back into place. It is stretched now and we don't have a machine like Aerovox, Mallory, or Astron. You can use some fine sandpaper to smooth scratches if you like. But once mounted, any damage will be right next to the phenolic washer.
Also, keep you eyes open for some NOS capacitors. Brand really doesn't matter because there was a lot of standardization of the mounting. You can cut open an NOS can and take the unused steel common connection mounting ring. That ring is often difficult to reuse. It will often break. And, if you have a new one, you can carefully twist back and forth the old ring to remove the cap from the wafer. But you must be careful or you will scratch and/or brake the wafer if not careful. Another reason for having some NOS old capacitors. They came with wafers in the box!
Here is another trick. If you have enough space, you could use a taller can if the new components don't fit exactly inside of the can. Yes, the markings may be wrong on the can though.
This is really helpful- thanks for the work involve in posting this. You did what appears to be a great job, and without sawing the can. Have you been able to use this method on most caps without sawing them, or do you come across a few that are too tricky to open up without sawing?
kvflyer
Super Member
The only cans that I have used a saw on were those that had the cardboard sleeve. You can cover the cut. But I even stopped doing that because of the need to "JB Weld" the can back together. But you can use that aluminum tape over the cut if you make it above the "step" in the can. Get an old can that you don't care about and try it! There is always the option of throwing it away. But be careful when you start to open the can. If you use the Xacto knife, have it on a piece of plywood, MDF, particle board etc. and work AWAY from yourself. Once you get that little lip up, you can start to work around the edge. You may even want to get a small cheap straight blade screwdriver and grind it into the size that works to continue uncrimping the edge.
Show us some pictures!
Beautiful work, I've re-stuffed a lot of cans and yours look way better. Thanks for the writeup!
One tip I have for removing the guts is if you don't mind having a small whole in the middle of the phenolic bottom (or if it has a vent hole there anyway) you can screw in a long wood screw and grab that in a vice.
One tip I have for removing the guts is if you don't mind having a small whole in the middle of the phenolic bottom (or if it has a vent hole there anyway) you can screw in a long wood screw and grab that in a vice.
kvflyer
Super Member
Yes, that will work also. And, if you have NOS cans that you want to use as donors, you can use the wafers with new lugs on them so you don't have to worry about the wafer in the can that you are rebuilding. Great ideas coming forth. I see some that use a cork screw to pull the guts out also.
oldtexasdog
Well-Known Member
Thanks for the pics and info. Nice work!:thmbsp:
