X-capacitor failure modes?

"Joerg"

> Is it possible that an X-cap self-heals to the point where you can
> barely see a thing, yet release a serious plume of smoke?

** Yep.


> It is a Rifa GPF-series film cap 0.22uF/250VAC with all kinds of agency 
> logos on there.

** I have been in the room twice when one of them blew itself up -  RIFA 
brand both times.

The first one was years ago inside a fan heater and the second in a portable 
TV late last year.

Filled the room with yucky smelling smoke and set off the alarm.



...  Phil

On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
wrote:

>Folks,
>
>This afternoon I took the old HP-4191A apart. Yesterday in the middle of
>some measurements it went pop-pop-pop, loud, like firecrackers. I ran
>over and turned it off, upon which the popping stopped. An immense
>amount of light-gray smoke wafted out and it had an odd stench to it.
>The stench lingered for hours.
>
>I can't find any source and upon powering it up the analyzer worked
>fine. That was before I changed anything. As if it had repaired itself.
>The only thing I could see is a crack in the plastic of the X-capacitor.
>Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
>than stated) and no leakage current. There is another X-cap and two
>Y-caps inside a canned IEC receptacle but those can't be the culprits
>because that is on the line side of the power switch.
>
>Is it possible that an X-cap self-heals to the point where you can
>barely see a thing, yet release a serious plume of smoke? It is a Rifa
>GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.

Never heard of Rifa GPF.

In fact, if it's Rifa, and manufactured since 1980, it's part type
will begin with the letter P, even after their amalgamation with Evox.

Metalized paper PM (or PZ), metalized polyester PH.

Perhaps you've mistaken the brand?

The 4191A was first released in 1980.

Interesting thing about the older Rifa parts, was that their outer
layer was transparent - an overstress or corona can often be seen, as
well as heard, but usually only in locations that are subject to the
attentions of overly zealous test technicians with manually adjustible
hipot equipment.

RL

Joerg wrote:

> Folks,
> 
> This afternoon I took the old HP-4191A apart. Yesterday in the middle of
> some measurements it went pop-pop-pop, loud, like firecrackers. I ran
> over and turned it off, upon which the popping stopped. An immense
> amount of light-gray smoke wafted out and it had an odd stench to it.
> The stench lingered for hours.
> 
> I can't find any source and upon powering it up the analyzer worked
> fine. That was before I changed anything. As if it had repaired itself.
> The only thing I could see is a crack in the plastic of the X-capacitor.
> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
> than stated) and no leakage current. There is another X-cap and two
> Y-caps inside a canned IEC receptacle but those can't be the culprits
> because that is on the line side of the power switch.
> 
> Is it possible that an X-cap self-heals to the point where you can
> barely see a thing, yet release a serious plume of smoke? It is a Rifa
> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
> 
Yes, definitely.  But, it is a bit surprising that it still has above
rated capacitance.  The crack in the plastic is pretty close to a
"smoking gun".  I have seen this before, at least once.

Jon

Spehro Pefhany wrote:
> On Sat, 21 Sep 2013 23:02:48 -0400, the renowned Martin Riddle
> <martin_rid@verizon.net> wrote:
> 
>> On Sat, 21 Sep 2013 22:28:54 -0400, Spehro Pefhany
>> <speffSNIP@interlogDOTyou.knowwhat> wrote:
>>
>>> On Sat, 21 Sep 2013 22:20:41 -0400, the renowned Martin Riddle
>>> <martin_rid@verizon.net> wrote:
>>>
>>>> On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> Folks,
>>>>>
>>>>> This afternoon I took the old HP-4191A apart. Yesterday in the middle of
>>>>> some measurements it went pop-pop-pop, loud, like firecrackers. I ran
>>>>> over and turned it off, upon which the popping stopped. An immense
>>>>> amount of light-gray smoke wafted out and it had an odd stench to it.
>>>>> The stench lingered for hours.
>>>>>
>>>>> I can't find any source and upon powering it up the analyzer worked
>>>>> fine. That was before I changed anything. As if it had repaired itself.
>>>>> The only thing I could see is a crack in the plastic of the X-capacitor.
>>>>> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
>>>>> than stated) and no leakage current. There is another X-cap and two
>>>>> Y-caps inside a canned IEC receptacle but those can't be the culprits
>>>>> because that is on the line side of the power switch.
>>>>>
>>>>> Is it possible that an X-cap self-heals to the point where you can
>>>>> barely see a thing, yet release a serious plume of smoke? It is a Rifa
>>>>> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
>>>> They are Self-Healing to the point that they don't pose a safety risk.
>>>> <http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf>
>>>>
>>>> Cheers
>>> Doesn't the UL standard prohibit "excessive" amounts of smoke? But
>>> those Rifa parts are pretty ancient. 
>>>
>>>
>>> Best regards, 
>>> Spehro Pefhany
>> Some smoke is ok, It is the flame and sustained smoking that throw red
>> flags for UL. X caps fail open, so they should not smoke for long.
>>
>> If Joerg left the power on long enough, he probably would not have
>> seen flames or more smoke. 
>>
>> I would have had a 'Oh sh... moment and turned the power off too" ;D
>>
>> Cheers
> 
> Presumably his immediate objective was to interrupt the proximate
> cause of the popping and smoking rather than to fully test those
> ancient capacitors to UL standards. ;-) 
> 

Yep. The smoking was quite intense, had to open the windows and leave
the lab area to avoid coughing. Plus the odor was really nasty.

-- 
Regards, Joerg

http://www.analogconsultants.com/

legg wrote:
> On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
> wrote:
> 
>> Folks,
>>
>> This afternoon I took the old HP-4191A apart. Yesterday in the middle of
>> some measurements it went pop-pop-pop, loud, like firecrackers. I ran
>> over and turned it off, upon which the popping stopped. An immense
>> amount of light-gray smoke wafted out and it had an odd stench to it.
>> The stench lingered for hours.
>>
>> I can't find any source and upon powering it up the analyzer worked
>> fine. That was before I changed anything. As if it had repaired itself.
>> The only thing I could see is a crack in the plastic of the X-capacitor.
>> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
>> than stated) and no leakage current. There is another X-cap and two
>> Y-caps inside a canned IEC receptacle but those can't be the culprits
>> because that is on the line side of the power switch.
>>
>> Is it possible that an X-cap self-heals to the point where you can
>> barely see a thing, yet release a serious plume of smoke? It is a Rifa
>> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
> 
> Never heard of Rifa GPF.
> 
> In fact, if it's Rifa, and manufactured since 1980, it's part type
> will begin with the letter P, even after their amalgamation with Evox.
> 


Maybe it's PME. The label says this:

Rifa    GPF
40/085/56
PME 271 M 622

Then also "CM1" rotated 90 degrees on the right. No Evox mention on there.


> Metalized paper PM (or PZ), metalized polyester PH.
> 
> Perhaps you've mistaken the brand?
> 

No, says Rifa on there and has the logo.


> The 4191A was first released in 1980.
> 

The service manual is from 1980 but I believe the machine itself was
built around 1985. It's a good system. Ok, had its quirks. A big
electrolytic in it gave up once. Then they had screwed up the backup
battery charger but since I fixed that it doesn't lose calibration data
anymore. The plastic component clamp levers for the 16092A probe head
are wimpy and, predictably, one snapped in half. Still usable but one
has to have strong fingernails. Other than that it has served me well.


> Interesting thing about the older Rifa parts, was that their outer
> layer was transparent - an overstress or corona can often be seen, as
> well as heard, but usually only in locations that are subject to the
> attentions of overly zealous test technicians with manually adjustible
> hipot equipment.
> 

This cap developed a crack across one of the flat sides. Considering the
loud pops and the amount of smoke I'd have expected a total meltdown but
other than the crack I can't see any damage.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Jasen Betts wrote:
> On 2013-09-21, Joerg <invalid@invalid.invalid> wrote:
>> I can't find any source and upon powering it up the analyzer worked
>> fine. That was before I changed anything. As if it had repaired itself.
>> The only thing I could see is a crack in the plastic of the X-capacitor.
>> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
>> than stated) and no leakage current. There is another X-cap and two
>> Y-caps inside a canned IEC receptacle but those can't be the culprits
>> because that is on the line side of the power switch.
>>
>> Is it possible that an X-cap self-heals to the point where you can
>> barely see a thing, yet release a serious plume of smoke? It is a Rifa
>> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
> 
> They're supposed to self heal
> 
> Smoke has low density, you can fit a lot of smoke precursor into a small space.
> 
> if it's got a crack it should definately be replaced, why not do some
> destructive testing and see if it can withstand the test voltage
> required and if it makes the right sort of wrong smell.
> 

It is rated 250VAC and I gave it 300VAC from my "Australia test setup".
No popping, no smell. But who knows, the suspect area might have already
vaporized itself.

-- 
Regards, Joerg

http://www.analogconsultants.com/

On Sun, 22 Sep 2013 07:24:35 -0700, the renowned Joerg
<invalid@invalid.invalid> wrote:

>
>Yep. The smoking was quite intense, had to open the windows and leave
>the lab area to avoid coughing. Plus the odor was really nasty.

http://fire.nist.gov/bfrlpubs/fire86/PDF/f86012.pdf

Some numbers on time to incapacitation and time to death in there. 



Best regards, 
Spehro Pefhany
-- 
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Spehro Pefhany wrote:
> On Sun, 22 Sep 2013 07:24:35 -0700, the renowned Joerg
> <invalid@invalid.invalid> wrote:
> 
>> Yep. The smoking was quite intense, had to open the windows and leave
>> the lab area to avoid coughing. Plus the odor was really nasty.
> 
> http://fire.nist.gov/bfrlpubs/fire86/PDF/f86012.pdf
> 
> Some numbers on time to incapacitation and time to death in there. 
> 

The two Labradors were smart and immediately left the area.  They must
have read it :-)

Such burning stuff can be dangerous, it has killed many travelers at
Duesseldorf airport, via smoke inhalation.

-- 
Regards, Joerg

http://www.analogconsultants.com/

On 9/22/2013 10:36 AM, Joerg wrote:
> legg wrote:
>> On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> Folks,
>>>
>>> This afternoon I took the old HP-4191A apart. Yesterday in the middle of
>>> some measurements it went pop-pop-pop, loud, like firecrackers. I ran
>>> over and turned it off, upon which the popping stopped. An immense
>>> amount of light-gray smoke wafted out and it had an odd stench to it.
>>> The stench lingered for hours.
>>>
>>> I can't find any source and upon powering it up the analyzer worked
>>> fine. That was before I changed anything. As if it had repaired itself.
>>> The only thing I could see is a crack in the plastic of the X-capacitor.
>>> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
>>> than stated) and no leakage current. There is another X-cap and two
>>> Y-caps inside a canned IEC receptacle but those can't be the culprits
>>> because that is on the line side of the power switch.
>>>
>>> Is it possible that an X-cap self-heals to the point where you can
>>> barely see a thing, yet release a serious plume of smoke? It is a Rifa
>>> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
>>
>> Never heard of Rifa GPF.
>>
>> In fact, if it's Rifa, and manufactured since 1980, it's part type
>> will begin with the letter P, even after their amalgamation with Evox.
>>
>
>
> Maybe it's PME. The label says this:
>
> Rifa    GPF
> 40/085/56
> PME 271 M 622
>
> Then also "CM1" rotated 90 degrees on the right. No Evox mention on there.
>
>
>> Metalized paper PM (or PZ), metalized polyester PH.
>>
>> Perhaps you've mistaken the brand?
>>
>
> No, says Rifa on there and has the logo.
>
>
>> The 4191A was first released in 1980.
>>
>
> The service manual is from 1980 but I believe the machine itself was
> built around 1985. It's a good system. Ok, had its quirks. A big
> electrolytic in it gave up once. Then they had screwed up the backup
> battery charger but since I fixed that it doesn't lose calibration data
> anymore. The plastic component clamp levers for the 16092A probe head
> are wimpy and, predictably, one snapped in half. Still usable but one
> has to have strong fingernails. Other than that it has served me well.
>
>
>> Interesting thing about the older Rifa parts, was that their outer
>> layer was transparent - an overstress or corona can often be seen, as
>> well as heard, but usually only in locations that are subject to the
>> attentions of overly zealous test technicians with manually adjustible
>> hipot equipment.
>>
>
> This cap developed a crack across one of the flat sides. Considering the
> loud pops and the amount of smoke I'd have expected a total meltdown but
> other than the crack I can't see any damage.
>

I had a very nice hand-wired Krohn-Hite filter croak itself a year or so 
back--the clamp on one of the 'computer-grade' filter caps was loose, 
and the cap worked its way down through the chassis till it shorted to 
the bottom of the case. (No fish paper there, for some silly reason.)

This resulted in clouds of transformer smoke filling the lab, which was 
a shame, because it was a really nice box and the transformer was an 
irreplaceable custom job.  It even had completely separate power 
supplies for the two channels, to prevent crosstalk.

Good thing I'm nuts about turning all the lab power off when I'm not 
there--it could have happened any time at all.

Cheers

Phil Hobbs



-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net

Phil Hobbs wrote:
> On 9/22/2013 10:36 AM, Joerg wrote:
>> legg wrote:
>>> On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
>>> wrote:
>>>
>>>> Folks,
>>>>
>>>> This afternoon I took the old HP-4191A apart. Yesterday in the
>>>> middle of
>>>> some measurements it went pop-pop-pop, loud, like firecrackers. I ran
>>>> over and turned it off, upon which the popping stopped. An immense
>>>> amount of light-gray smoke wafted out and it had an odd stench to it.
>>>> The stench lingered for hours.
>>>>
>>>> I can't find any source and upon powering it up the analyzer worked
>>>> fine. That was before I changed anything. As if it had repaired itself.
>>>> The only thing I could see is a crack in the plastic of the
>>>> X-capacitor.
>>>> Snipped the thing out, measured, has almost 0.28uF capacitance (27%
>>>> more
>>>> than stated) and no leakage current. There is another X-cap and two
>>>> Y-caps inside a canned IEC receptacle but those can't be the culprits
>>>> because that is on the line side of the power switch.
>>>>
>>>> Is it possible that an X-cap self-heals to the point where you can
>>>> barely see a thing, yet release a serious plume of smoke? It is a Rifa
>>>> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on
>>>> there.
>>>
>>> Never heard of Rifa GPF.
>>>
>>> In fact, if it's Rifa, and manufactured since 1980, it's part type
>>> will begin with the letter P, even after their amalgamation with Evox.
>>>
>>
>>
>> Maybe it's PME. The label says this:
>>
>> Rifa    GPF
>> 40/085/56
>> PME 271 M 622
>>
>> Then also "CM1" rotated 90 degrees on the right. No Evox mention on
>> there.
>>
>>
>>> Metalized paper PM (or PZ), metalized polyester PH.
>>>
>>> Perhaps you've mistaken the brand?
>>>
>>
>> No, says Rifa on there and has the logo.
>>
>>
>>> The 4191A was first released in 1980.
>>>
>>
>> The service manual is from 1980 but I believe the machine itself was
>> built around 1985. It's a good system. Ok, had its quirks. A big
>> electrolytic in it gave up once. Then they had screwed up the backup
>> battery charger but since I fixed that it doesn't lose calibration data
>> anymore. The plastic component clamp levers for the 16092A probe head
>> are wimpy and, predictably, one snapped in half. Still usable but one
>> has to have strong fingernails. Other than that it has served me well.
>>
>>
>>> Interesting thing about the older Rifa parts, was that their outer
>>> layer was transparent - an overstress or corona can often be seen, as
>>> well as heard, but usually only in locations that are subject to the
>>> attentions of overly zealous test technicians with manually adjustible
>>> hipot equipment.
>>>
>>
>> This cap developed a crack across one of the flat sides. Considering the
>> loud pops and the amount of smoke I'd have expected a total meltdown but
>> other than the crack I can't see any damage.
>>
> 
> I had a very nice hand-wired Krohn-Hite filter croak itself a year or so
> back--the clamp on one of the 'computer-grade' filter caps was loose,
> and the cap worked its way down through the chassis till it shorted to
> the bottom of the case. (No fish paper there, for some silly reason.)
> 
> This resulted in clouds of transformer smoke filling the lab, which was
> a shame, because it was a really nice box and the transformer was an
> irreplaceable custom job.  It even had completely separate power
> supplies for the two channels, to prevent crosstalk.
> 
> Good thing I'm nuts about turning all the lab power off when I'm not
> there--it could have happened any time at all.
> 

Still, watch those X-caps in them boat anchors where you now have so
many of. I have seen these golden-clear plastic caps in many of them. My
lab has pretty good line spike filtering and the cap ran at less than
50% of its rated voltage yet it decided to blow. Problem is, things such
as this impedance analyzer can be unattended for long periods of time
when you run an experiment. Same with a spectrum analyzer when it runs a
baseline scan over a 100MHz swath with 1Hz BW. You don't want to come
back from lunch only to see trucks with flashing blue lights surrounding
your building because a fire alarm went off.

-- 
Regards, Joerg

http://www.analogconsultants.com/