RCA 621TS restoration -- in pictures

[kvflyer]

Originally Posted by M3-SRT8

Nice work, Tom.

Have you tried those Nichicon and Panasonic narrow diameter electrolytics? You can get them with great life and temperature ratings (105 C), high voltages, radial leads, and they are just the trick for restuffing cans.

They are long and narrow, say 12.5 or 16mm diameters, and I habitually use the 350v and 450v versions, for a margin of protection.

At Mouser Electronics, naturally.

Agree! I have some and they fit nicely with room to spare. I wish that they made some 500 WVDC versions for use in audio amp power supplies.

[charokeeroad]

Really slow and meticuluous work Tom but on a set like that one all the care is well deserved.

Just wondering if a bead of sliver solder in paste around the reconstructed seam on the aluminum cans would give a cleaner look to the joint and if it might be stronger as well. Of course that presupposes that aluminum can be sliver soldered. I have used silver solder in paste that comes in a syringe for easy application but I don't think I've ever tried it on aluminum. If the can isn't pure aluminum but an aloy it just might stick. Silver solder has a very low melting temperature as compared to other solders. Not sure if a good high temperature heat gun would provide enough heat to melt it but a wave of a flame from a mini torch would certainly do it. If one were to position the cut in the can where the entire joint was horizontal as opposed to vertical the chances for success would be better too I would think.

Keep up the good work.

[Phil Nelson]

If you make a clean cut and use JB Weld to reglue the can, the seam will be nearly invisible. The color of the epoxy is similar to the can color. Wipe excess glue from the seam.

Phil Nelson

[kvflyer]

And for what it is worth, here is how I try to do it. But if there is a paper sleeve, it only makes sense to cut the cap off because you will never see it under the cardboard!

http://www.audiokarma.org/forums/sho...12#post5772312

[Tom Albrecht]

All the ones I cut have black paper sleeves, so the modification is not visible at all on those. For the one without paper sleeve, my JB Weld is on the bottom of the can, which is also not visible at all when it is mounted in the set. So no visible sign of modification.

I like what you've shown, kvflyer. Maybe next time I'll try to uncrimp the flange the way you've shown. That method does not leave the bottom of the can visibly messed up. The easier way to uncrimp using a diagonal cutters lifting the flange leaves quite a bit of scarring on the OD at the bottom. Your method looks better. Should be nice and strong when finished.

I must say, however, it's a fair amount of work. I'm not likely to routinely restuff cans for my own sets. But happy to do it by special request for others.

Lee,

Thanks for the tip on the Panasonic caps. For the five cans I restuffed on this one, only one can was difficult to fit the replacements in. All the rest had tons of room, so it didn't matter what kind of caps I had. Good to know about the Panasonics for those that are short on space.

John,

I'm not aware of any easy way to solder aluminum. Pretty sure the silver solder won't stick.

[Tom Albrecht]

The electrolytic cans have all been restuffed and are back in place on the chassis. No visible sign that they've been touched:



Today I did most of the paper cap restuffing. Here's the starting point -- a new yellow cap and the old cap it needs to end up inside:



OK, I realize 0.22 uF is not quite exactly the same as 0.25 uF, but it does work very nicely in the set, so this is close enough.

I started by heating the caps a few at a time in the kitchen oven at 300 F for 15 minutes. This melts the sealing wax at the ends of the caps so that the old cap innards can be pushed out one end:



Although the wax coating on the outside of the capacitor melts at a much lower temperature, the sealing wax needs to get pretty hot to melt. Unfortunately, this means that the coating wax is pretty much lost. I'll coat them with new wax at the end of the process.

Once the cardboard tube is clean, I clamp the new capacitors upright in a vise, and stand the cardboard tubes up around them so they are ready to be filled with hot melt glue:



I squirt enough glue in to fill the end. I find it looks better if I reflow the glue with a heat gun after I am done dispensing with the hot glue gun. Sometimes it settles a bit and more has to be added.

I had two colors of hot glue sticks -- neither of which is ideal. I started with some light amber sticks, but decided it comes out too light colored. The other option I have is brown, which is darker than ideal, but I decided I like it better than the light amber. After wax coating, maybe these will resemble the originals.

Take a look yourself and see which color you like better:



Here's all the paper caps in their current state:



Tomorrow if I have time I will coat all of them with a fresh coating of beeswax. The slightly cloudy color of the beeswax should help them look a bit more like the originals. Right now, they are "too clean."

I'll post some more pictures after the wax coating.

[jmetal88]

Wow, you're really committed to original appearance!

I just did my first re-cap, and I didn't even leave the electrolytic cans in place. I have the modern electrolytics mounted in clusters above the chassis where the cans used to be. I guess that's about as far from original as I can get, haha.

[ChrisW6ATV]

Very nice work on those capacitors, Tom!

I like the brown glue much better than the other, which appears white to me.

[snelson903]

i like that ,useing the old paper style cap. and inserting a new one inside . some of the old paper cap had a cool look ,i have some new old stock caps i threw away they all tested bad naturaly but i like the look of them , man now im going to dig them out of the trash bag.

[kvflyer]

I have saved a lot of paper caps for the appropriate application (which hasn't presented itself yet!). I also ran into the end filling color issue. I tried saving the stuff and melting it but it just seems to never be enough. I got some sorta brown hot melt glue and it is better but still not what I think is the correct color. Guess I need to do some more looking on the Internet.

One thing that seems to be a problem is that the high value capacitors seem to have leads that are often too short given that the original capacitor was usually so large (read, LONG) and was able to reach from terminal to terminal. I have bought some tinned wire and thought that maybe the leads could be lengthened inside of the rebuilt paper cap.

What is the general opinion on how to deal with that issue?

[kvflyer]

One other thing that I do is to save all of the vintage spaghetti that I can get my hands on since most of what is out there is white. I do have a link for some in the Mouser catalog but have not ordered any yet. Anyone else have ideas on this too?

[charokeeroad]

Nice work Tom, a new coat of 100% beeswax should do the trick. Same color and consistancy as what I see in the pictures of the original caps and know from my own handeling of them. The opacity seems to match as well given the same thickness. Beeswax would have been readily available in the mid to late 40s. Especially like the chassi pic and the last pic with all the refilled caps you posted a 2:03am.

You were up late last night!

[charokeeroad]

"I have bought some tinned wire and thought that maybe the leads could be lengthened inside of the rebuilt paper cap."

Kvflyer, That soulds like a winner to me.

[kvflyer]

Originally Posted by charokeeroad

"I have bought some tinned wire and thought that maybe the leads could be lengthened inside of the rebuilt paper cap."

Kvflyer, That soulds like a winner to me.

So, is it just me or are the modern day large value capacitors usually "too short" to be used in the factory location? And, I wonder if the layout of the vintage chassis was such that the larger caps (read longer length) would work? I know if you are replacing a .5 uFD @ 400 WVDC, it just may have been held in with a clamp! I did an Admiral that had some capacitors held in with a clamp. I didn't rebuild the original. But you can believe I saved them.

But again, nice, nice work. I love not only the look of the rebuilt electrolytic capacitors but also the rebuilt paper capacitors.

[Reece]

Length of the old vs new caps works both ways. Sometimes you see a large old cap with the leads bent back under because it's going to two closely spaced terminals. The new smaller cap would fit better.

Lengthening new cap leads with tinned wire is fine: an easy way is to form a "squib" from one of the wires, a tight little coil of several turns that fits around the other wire, and then is soldered. Forms a good connection. When restuffing the squib can hide inside the outer shell and no one will know...