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  #1  
Old 10-04-2009, 01:20 AM
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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
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  #2  
Old 10-04-2009, 04:37 AM
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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.
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Old 10-04-2009, 08:51 AM
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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?
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  #4  
Old 10-04-2009, 10:58 AM
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Excellent and tidy work, Doug. Another vote for a sticky.
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Old 10-04-2009, 12:59 PM
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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:

Quote:
Note the leads that were routed up through the wafer board. The goal here was not to solder leads on the opposide side of the wafer. Last thing you want is to solder the wires back to the cap but have the solder melt off the other end where you have no ability to gain access to them.
Thanks for the photostory!
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Old 10-04-2009, 02:33 PM
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Bravo
Yes, sticky please. Perhaps relocate to the Vintage TV & Radio Tech Forum ?
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  #7  
Old 10-04-2009, 03:42 PM
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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,
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Old 10-04-2009, 06:09 PM
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What a great teacher you are. I certainly learned somethng new today!
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Old 10-05-2009, 08:52 PM
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Quote:
Originally Posted by Findm-Keepm View Post
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?
I found this - apparently Sprague derates the caps too:

TVL-4813.2 80/4+4/200uF 475/450+450/25VDC
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  #10  
Old 03-07-2011, 11:24 PM
radiorich radiorich is offline
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Hello Guys,
I do mine almost the same but I just don't do the foam thing

Well done thinks for that slideshow
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  #11  
Old 09-04-2011, 09:37 PM
Tom_Ryan Tom_Ryan is offline
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Quote:
Originally Posted by radiorich View Post
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.
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  #12  
Old 09-05-2011, 02:01 PM
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I tend to wrap the new innards in electrical tape instead of foaming the can.
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  #13  
Old 09-05-2011, 10:03 PM
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Robert Grant Robert Grant is offline
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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?

Last edited by Robert Grant; 09-05-2011 at 10:04 PM. Reason: added spacer lines since forum deletes the indents
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  #14  
Old 09-06-2011, 01:44 AM
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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.
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  #15  
Old 11-29-2011, 12:24 PM
chipper chipper is offline
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Is it ok to drop your caps in the can and then surround them with CLEAR SILICONE?
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