How to rebuild a filter capacitor
 

I rebuilt a filter capacitor and took some detail pictures on how to do it and the procedure to do it. The cap show is for Carmines 24NC31 chassis Zenith. Hopefully this helps those who are curious and want to try it out. They're fun to rebuild, like a small puzzle to see how you can make it all work.

http://www.picturetrail.com/sfx/album/view/22501148

Doug, very nice presentation, you do neat work.
I never realized the mounting ring was a separate piece, I've always cut it off above the step, I'll have to try this method the next time.

This is such a common subject that comes up I think it should be a Sticky.

Yes, that's a great presentation! I haven't tried doing this, but after seeing your steps, I might have to give this a whirl.

Curious... how long does it take you start to finish?

Excellent and tidy work, Doug. Another vote for a sticky. :yes:

Wow Doug... Fantastic work.

I will admit that I was curious why you went to the trouble of hooking the leads through the bottom of the wafer insulator, until you explained it:

Thanks for the photostory!

Bravo http://www.jawaspot.com/smilies/clap.gif
Yes, sticky please. Perhaps relocate to the Vintage TV & Radio Tech Forum ?

Doug,

I noticed the original 4uF sections were rated at 475V, but the replacements are 450V - can they be de-rated like that in that chassis?

Cheers,

What a great teacher you are. I certainly learned somethng new today!

I found this - apparently Sprague derates the caps too:

TVL-4813.2 80/4+4/200uF 475/450+450/25VDC

Hello Guys,
I do mine almost the same but I just don't do the foam thing

Well done thinks for that slideshow

Yep, same here. I avoid use of foams for cap rebuilds mostly because as the foam ages it breaks down. Once sealed inside, the new caps gradually give off gases very slowly that may attack the foam.

Also, didn't see this mentioned in the presentation, I prefer using new 105 deg C rated capacitors and not the cheap 85 deg C consumer stuff when doing the rebuild.

I tend to wrap the new innards in electrical tape instead of foaming the can.

Can anyone summarize the advantages/disadvantages of placing new electrolytics in the old cans versus hiding modern caps under the chassis (as I have done on a few Zenith T/Os, a 1935 RCA console radio, and a few others)?

Which gets hotter, the space under the chassis, or inside a can with other caps?

More electrolytic questions:

- The voltage doubler circuit in the Zenith color roundie I am about to re-cap (24MC32 chassis, Photofact 769-4) uses an oddball value of 160μfd - can I safely take it up to 220μfd? (I might mention here that the doubler is unusually working from the secondary of a power transformer - not directly from the line as voltage doublers usually are).

- Do I need a high-current capacitors in this application since they are actually providing the B+, not just filtering it?

- A cap in the 120 volt source is specified as 4μfd at 475V! Is there some reason I need 475 V, or did the multi-cap C3 just happen to have an extra 4μfd cap at 475V so the design engineers use that one there?

If there aint much space under the chassis which often is the case with color sets, then restuffing makes the job neater and all the benifits that come with that.

Is it ok to drop your caps in the can and then surround them with CLEAR SILICONE?

If you silicone them in it will be harder to rebuild the can again, and most caps these day are not designed to last the lifetime or three that these sets are likely to be kept around in the collector comunity.

What I do is to arrange my caps together so that they will fit in the can. Then wrap them in electrical tape 1 layer thick( thicker than that on the exposed metal surfaces of course). And wire them to the old phenolic base.

I just got a good idea for you to try. Get a toilet paper roll and cut a stripe along it's length and glue the edges together so that it can be slid in and out of the can cut a piece of card board out and glue it in to seal the top squirt some silicone in the bottom of the cardboard tube, put the caps in before it begins to dry, then squirt some more silicone in after the caps are in. This should give you a card board tube that can easily be pulled out of the can in the future and which should posess whatever benifits you hope to gain from the silicone potting.

Just some thoughts.

How about some shrink tubing around the bundle of capacitors? That's what the manufacturers use to cover the outer aluminum case anyway.

Wouldn't it be nice if someone could make new empty cans with a threaded base? THsat way you can get back into them easier in the future.

Hi All;
DRH4683, You make it look so easy.. But, I am sure that it isn't as easy as it looks.. I think that taking out the inner ring, which is the first step, would be the hardest, I would be afraid of breaking the bottom plastic piece..
THANK YOU Marty

Hi Is there a number to reach you at?Doug have a question about a zenith color also need a knob if you can help. Is there a number to reach you at?

Hi Doug I have a question about a early zenith color set. Also a small knob missing if you can help. Is there a number to reach you at? Maybe you can help, they say your the zenith master. Henry

Here's a good video showing the uncrimping technique: http://youtu.be/azc2RRQw6Tk

Its better late then never. Thanks Doug.I used your tips on restuffing a power supp elecro cap in a 1967 Motorola stereo record player last summer.

I'm glad I did the job outside due to the horrible small they put off.

The record player sounds great now.

This is an old thread, but its the proper place to ask.

How do you do the first step, uncrimping the lip, NEATLY?

I tried very hard tonight and failed. I could find no way to get
the crimp started at all without a big mess. I could find
no way to get even the tiniest knife under the lip.
Help!

Doug McDonald

There's no real way to do it neatly. The lip is generally not visible once installed so mutilation isn't a big deal, just try and avoid chewing up the sides. :thmbsp:

I just finished my can and want to thank the OP for this guide.

In my case, however, removing the innards was not nearly so simple. It took me a good hour or so to get it all out and used my heat gun on high for MANY minutes in total. So much tar and it just wouldn't release. I had to drill out as much of the innards as I could and that went a long way to getting it done but it was still quite an effort even after that.

Also, sadly 3 of the 4 tabs that hold the can to the chassis broke because of being too weak. I had to solder the stubs in the holes of the chassis to anchor the can to the chassis. So be careful with those tabs!

Earlier, someone asked about using silicone. if you do use it, make sure you order electronics grade silicone. hardware store silicone is acid cure, and the acid will eventully corrode your wire.