Exploding X2 capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

collisr · 5th Sep 2017, 5:39 pm

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

G6Tanuki · 5th Sep 2017, 5:50 pm

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!]

evingar · 5th Sep 2017, 5:51 pm

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

turretslug · 5th Sep 2017, 5:52 pm

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.

yampy187 · 5th Sep 2017, 5:53 pm

Quote:

Originally Posted by G6Tanuki

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.

Agreed! Modern x2 replacements are cheap enough.. pence, infact.

Regards,

Jan

HamishBoxer · 5th Sep 2017, 6:39 pm

£6 pound for ten when I repaired the church organ that had gone up in smoke.

MrBungle · 5th Sep 2017, 6:41 pm

Been buying these. Cost virtually nothing:

https://www.bitsbox.co.uk/index.php?...fuufs824u4njj3

collisr · 5th Sep 2017, 6:45 pm

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

MrBungle · 5th Sep 2017, 6:53 pm

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.

PsychMan · 5th Sep 2017, 7:59 pm

Quote:

Originally Posted by G6Tanuki

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.

Agreed! NOS capacitors are a big con as far as Im concerned

HamishBoxer · 5th Sep 2017, 8:09 pm

Wima are certainly dodgy. NOS for most things. But caps!

Refugee · 5th Sep 2017, 11:25 pm

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!

MrBungle · 5th Sep 2017, 11:39 pm

Impressive failure mode!

Another discussion on the X2 capacitors here with gruesome pictures: https://www.vintage-radio.net/forum/...ad.php?t=69128

Maarten · 6th Sep 2017, 3:39 am

Quote:

Originally Posted by HamishBoxer

Wima are certainly dodgy. NOS for most things. But caps!

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.

Maarten · 6th Sep 2017, 3:44 am

Quote:

Originally Posted by Refugee

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!

10 years seems a bit long to me, as those original type paper capacitors are apparently qiute sensitive to environmental conditions (temperature changes while not in use perhaps). Just replace them with polypropylene types (MKP) from a decent brand (WIMA, Vishay, Epcos, Panasonic) and never look back. No need for maintenance then.

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.

hannahs radios · 6th Sep 2017, 11:32 pm

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.

5th Sep 2017, 5:39 pm	#1
collisr Pentode Join Date: Oct 2016 Location: Ware, Herts, UK Posts: 171	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
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,995	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
evingar Octode Join Date: Oct 2003 Location: Newbury, Berkshire, UK. Posts: 1,770	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 __________________ Chris

5th Sep 2017, 5:52 pm	#4
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,394	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, 6:39 pm	#6
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Exploding X2 capacitors £6 pound for ten when I repaired the church organ that had gone up in smoke. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

5th Sep 2017, 6:41 pm	#7
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Exploding X2 capacitors Been buying these. Cost virtually nothing: https://www.bitsbox.co.uk/index.php?...fuufs824u4njj3

5th Sep 2017, 6:45 pm	#8
collisr Pentode Join Date: Oct 2016 Location: Ware, Herts, UK Posts: 171	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 Attached Thumbnails

5th Sep 2017, 6:53 pm	#9
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	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.

5th Sep 2017, 8:09 pm	#11
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Exploding X2 capacitors Wima are certainly dodgy. NOS for most things. But caps! __________________ G8JET BVWS Archivist and Member V.M.A.R.S

5th Sep 2017, 11:25 pm	#12
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	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
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	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, 11:32 pm	#16
hannahs radios Hexode Join Date: Jan 2012 Location: Weymouth, Dorset, UK. Posts: 422	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.