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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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5th Sep 2017, 5:39 pm | #1 |
Pentode
Join Date: Oct 2016
Location: Ware, Herts, UK
Posts: 171
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Exploding X2 capacitors
Hi all - wondered if the community might be able to advise me.
After many years collecting various formats of video tape, finally got round to attempting digital transfers. With help from some of the community here and PALsite, been able to fix a great deal of players, but been finding Video 2000 players a real pig! Anyways.. to my current problem. And remember, I am an amateur with under a year of experience in these things, so please be gentle with me. My latest acquisition (a Grundig 2x4 Super Video 2000 player) keeps blowing it's X2 mains capacitors and I don't know why. I sort of expected it's original one to blow (it lasted about 30 mins) during the start of my renovation. It has 2 X2 caps (0.47uF/250v ; 0.22uF/250v) and the latter had shattered. I ordered some NOS caps from a certain auction site and I replaced both. The .22uF is a "modern" yellow, square type but the .47uF looks like an original WIMA MP3 - identical to the original 35yo one. Upon re-connecting the machine, this WIMA replacement NOS also exploded after about 5 mins. My question: Have I been unlucky in buying a dud NOS cap or should I be checking something else isn't wrong? According to the service manual, both these caps are the first things the mains connector hits (there is no old-school transformer in these Grundigs). Any help gratefully appreciated. Rob |
5th Sep 2017, 5:50 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,998
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Re: Exploding X2 capacitors
Stop buying NOS capacitors!
You have no idea how they've been stored, and they're likely to have suffered age-related degradation like the ones originally fitted in your player, so you're replacing a failed-part with one that's just-about-to-fail. [Personally, I see "new old stock" as being something to avoid in components wherever possible, just as you would with packets of sausages!] |
5th Sep 2017, 5:51 pm | #3 |
Octode
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
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Re: Exploding X2 capacitors
It is difficult to see what else can be blowing these caps up if they are merely fitted across the incoming mains. I think you have just been unlucky.
I would strongly recommend that you buy replacement X2 caps as newly manufactured components from a reputable vendor such as RS or Farnell
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Chris |
5th Sep 2017, 5:52 pm | #4 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,395
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Re: Exploding X2 capacitors
Are the Wimas (old and new) the type with a translucent encapsulation with the label under it (like reading a newspaper at the bottom of a swimming pool....)? If so, they suffer the same problem as Rifa types (search both this forum and the wider world on their shortcomings!). The epoxy? encapsulant seems to have poor expansivity characteristics, developing fine cracks and allowing water vapour/moisture into the innards with often smelly, sometimes spectacular results. Even NOS can suffer this, sometimes in short order, as your experience has proved. It seems that these types use a dielectric that is at least partly paper with its poor moisture resistance and degradation.
It's a case of looking out an appropriately rated X type of a different construction- or making sure that replacement Wima/Rifa types are genuinely of recent manufacture and resigning yourself to sporadic replacement. Fortunately, they don't actually seem to burn when they fail, though the ones inside mains filters can burst with some force. |
5th Sep 2017, 5:53 pm | #5 | |
Hexode
Join Date: May 2010
Location: Coventry, Warwickshire, UK
Posts: 374
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Re: Exploding X2 capacitors
Quote:
Regards, Jan |
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5th Sep 2017, 6:39 pm | #6 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,932
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Re: Exploding X2 capacitors
£6 pound for ten when I repaired the church organ that had gone up in smoke.
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G8JET BVWS Archivist and Member V.M.A.R.S |
5th Sep 2017, 6:41 pm | #7 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Exploding X2 capacitors
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5th Sep 2017, 6:45 pm | #8 |
Pentode
Join Date: Oct 2016
Location: Ware, Herts, UK
Posts: 171
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Re: Exploding X2 capacitors
Thanks all. I sorta suspected this may be the case.
I have attached a pick of the NOS X2 which has blown. To be fair, I have had trouble finding a replacement with a 27.5mm lead pitch. Hence the NOS. I have found an X1 equivalent (that is cheap) which has the correct shape and size to fit in the Grundig power board. As evingar has said - "I can't see what else can be causing it". But then again... I hadn't even heard of an X2 capacitor three months ago. Rob |
5th Sep 2017, 6:53 pm | #9 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Exploding X2 capacitors
I just bend the leads out slightly on the 22mm ones. I'd rather it was a couple of mm off the board if it goes boom.
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5th Sep 2017, 7:59 pm | #10 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
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Re: Exploding X2 capacitors
Agreed! NOS capacitors are a big con as far as Im concerned
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5th Sep 2017, 8:09 pm | #11 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,932
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Re: Exploding X2 capacitors
Wima are certainly dodgy. NOS for most things. But caps!
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G8JET BVWS Archivist and Member V.M.A.R.S |
5th Sep 2017, 11:25 pm | #12 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,553
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Re: Exploding X2 capacitors
I have got in my museum of duff stuff a couple of WYMA X-2 caps that are NOS.
They have split open while just laying in a drawer never having been soldered into anything. Just buy new ones and mark your VCR with a date for them to be replaced again to stop the smoke. Perhaps after 10 years. I have had one go off in a vacuum cleaner. Now that really did stir the smoke up! |
5th Sep 2017, 11:39 pm | #13 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Exploding X2 capacitors
Impressive failure mode!
Another discussion on the X2 capacitors here with gruesome pictures: https://www.vintage-radio.net/forum/...ad.php?t=69128 |
6th Sep 2017, 3:39 am | #14 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,199
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Re: Exploding X2 capacitors
It's not WIMA in particular nor is it caps in general that one shouldn't buy NOS. The problem is very specific, limited to all capacitors with paper dielectric in general that won't last as long (in stock or intermittent use) as polyester and polypropylene types and more specifically and dramatically all semitranslucent ones by WIMA (MP3 series) and Evox/RIFA (countless series) of which the life span seems even shorter and less predictable than that of paper capacitors in general. I've given up on RIFA in general, but WIMA is known to produce some of the best polypropylene capacitors so I generally trust them.
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6th Sep 2017, 3:44 am | #15 | |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,199
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Re: Exploding X2 capacitors
Quote:
The MKP capacitors in the Bitsbox link aren't of a reputable brand so they might drift towards open circuit a bit faster than expected (depending mostly on mains spikes) but they won't fail spectacularly. |
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6th Sep 2017, 11:32 pm | #16 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Re: Exploding X2 capacitors
Totally agree with the above comments. Any capacitor that's been hanging about for more than a year should be treated with caution, with high voltage ones it might be a good idea to wake it up SLOWLY on a variac or lamp limiter, once its fitted to the equiplment, to avoid the shock of suddenly seeing 240 volts.
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