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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 1:18 am 
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Joined: Sep Fri 07, 2007 2:27 am
Posts: 5929
Location: Grand Chute, Wisconsin
Got a call one day to look at an RCA radio. Seller decided to warm up the radio while I was driving over. This is what I saw when I got there. I ended up buying it for far less than he originally asked for.



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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 2:08 am 
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Joined: Aug Tue 24, 2010 8:56 pm
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Location: Northeast Florida
:shock:

I hope the power trans was ok! I'd leave the boric acid stain--it adds to it's heritage :D

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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 3:39 am 
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A radio with a chimney .... just when you think you've seen it all ...

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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 11:41 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1382
Location: Arlington, VA USA
ktewell wrote:
My first and hopefully last cap blast. I almost had to change my underwear. That’s all the paper under it. It was on for awhile then bang.


So was it in backward? I see those are the Miec brand. I always wondered if those were reliable?


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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 12:19 pm 
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Joined: Apr Thu 18, 2013 2:43 am
Posts: 1065
Location: Cincinnati, Ohio
Is this correct? if so, I had it backwards.


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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 1:06 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1025
Location: St. Louis, MO, USA
I have a Lafyette LSG-10 signal generator that I have used for many years with no problems. Last year it quit cold. When I opened it, there were 2 modern filter caps that had blown up. It seems the previous owner had mistakenly put 40 uF 10 WV ones in instead of 10uF 400 WV. How it worked that long is a mystery.

Dennis


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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 4:20 pm 
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Location: Dayton Ohio
ktewell wrote:
Is this correct? if so, I had it backwards.


Actually, the way you have it marked IS backwards.

The center tap of the HV winding is negative, the filament of the 80 is positive.

Even if you had it correct, sometimes there is more than 450 volts right at the first filter cap between the CT and rectifier.
That will indeed push the cap past its limit.

-Steve

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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 4:28 pm 
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Location: Cincinnati, Ohio
Then I had it right and it popped anyway. Because, I had it opposite of the drawing above when it popped. Should I get a 600 volt cap?

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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 4:31 pm 
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Location: Maryland 20709, USA
ktewell wrote:
Then I had it right and it popped anyway. Because, I had it opposite of the drawing above when it popped. Should I get a 600 volt cap?
Hi Kevin,

The WVDC rating of a capacitor is the DC voltage PLUS the peak ripple voltage. For the cap at the rectifier cathode, the ripple voltage may be quite significant. You can measure it with a peak-reading AC voltmeter.

- Leigh

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 Post subject: Re: Capacitor blowup
PostPosted: May Thu 16, 2019 4:40 pm 
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Posts: 18192
Location: Dayton Ohio
ktewell wrote:
Then I had it right and it popped anyway. Because, I had it opposite of the drawing above when it popped. Should I get a 600 volt cap?


Yes, i would reccomend a 600 volter there. 4 uf is small enough you could easily find a mylar or poly cap.
https://www.tubesandmore.com/products/c ... ylene-fast
The 4.7 uf is $5.10.

Or put two 2.2 uf 630V yellow ones in parallel with each other. Ends up being about the same price.

http://www.radiodaze.com/axial-film-2-2mf-630v/

-Steve

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 Post subject: Re: Capacitor blowup
PostPosted: May Fri 17, 2019 3:32 am 
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Posts: 352
Location: brownsville, kentucky 42210
i use sprague atom capacitors they have never gave me a problem.

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