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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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11th Jul 2017, 4:15 pm | #1 |
Octode
Join Date: Jul 2011
Location: Leicester, Leics. UK.
Posts: 1,685
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Rejuvenating condensers
I came across this interesting wrinkle in a 1935 Practical Wireless. It might not be practical for the smaller cylindrical jobs, but I'm wondering if it might be worthwhile for the larger sort in tins, including the multiple capacitors. I have heard of people drying out waxies, this seems a further process. I would guess it would be done if there was much value in it.
Tony |
11th Jul 2017, 4:37 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
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Re: Rejuvenating condensers
Fascinating...! Just goes to see that the "make-do-and-mend" attitude predates WWII.
Must admit, I've wondered whether there could be a market to sell old "Vacuum-reclaimed" waxies back into the hardcore audiophile community. Sticking them [the waxies, not the audiophiles that is] into a vacuum-chamber and using a turbomolecular pump to wind them down to 100 nanoPascals for a day or so should get any absorbed/adsorbed dampness out of the paper dielectric and bring about a several-hundred-fold increase in their resale value! |
11th Jul 2017, 5:06 pm | #3 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
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Re: Rejuvenating condensers
Now that's what I call a proper repair!
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11th Jul 2017, 5:25 pm | #4 | |
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Re: Rejuvenating condensers
Quote:
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11th Jul 2017, 5:47 pm | #5 |
Pentode
Join Date: Jul 2015
Location: Newbury, Berkshire, UK.
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Re: Rejuvenating condensers
I am wondering what chemical raction could occur between aluminum plates and wax to create bubbles of a gas?
I am thinking about one that cannot be spotted during long term testing, maybe hydroxides in the wax ? |
11th Jul 2017, 6:12 pm | #6 |
Octode
Join Date: Jul 2011
Location: Leicester, Leics. UK.
Posts: 1,685
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Re: Rejuvenating condensers
If you drop anything - such as wooden or cardboard coil formers - into hot molten wax, the moisture boils off as a gas and bubbles up and away. I don't know how permanent this is, but would guess it could be as 'good as new'. Maybe a decade or two? I suppose this isn't as good for reliability as replacement with a modern component, but it does preserve the original more completely and could possibly be repeated!
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11th Jul 2017, 6:21 pm | #7 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Rejuvenating condensers
It's not just the effect of moisture ingress: Waxes can degrade with age and their conductive/dielectric properties change: I've had plenty of trouble in times past with the "wax" that Japanese radio-manufacturers slathered over the RF tuned-circuits in VHF/FM tuners and amateur-radio gear in the 1970s and 1980s. It degrades and can cause sufficient loss-of-Q in tuned-circuits to stop VFOs and crystal-oscillators from oscillating, and cause enough damping to mean you lose tens-of-dB of sensitivity if this stuff's still on the RF front-end circuits.
I don't like wax, or waxies. |
11th Jul 2017, 6:27 pm | #8 |
Pentode
Join Date: Jul 2015
Location: Newbury, Berkshire, UK.
Posts: 243
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Re: Rejuvenating condensers
Just moisture absorbed by wax ? OK, I thought there was some small gas bubbles on the plates.
I would apply the same HV to both terminals to separate the plates evenly (when hot). Thank you, Jacek PS :Sounds like a good idea for a good valve amp bussiness : original waxies, carbon resistors, transformers, high voltage, valves, lots of heat (I don't care, got AirCon, because there is too much heat from my oil rigs) |
11th Jul 2017, 6:44 pm | #9 | |
Dekatron
Join Date: May 2008
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Re: Rejuvenating condensers
Quote:
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11th Jul 2017, 6:58 pm | #10 |
Octode
Join Date: Jul 2011
Location: Leicester, Leics. UK.
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Re: Rejuvenating condensers
I guess the thing is to try and see how well it works. I am thinking of the often green rectangular tin things found in early 30's sets. When I have chance I will do so!
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11th Jul 2017, 7:24 pm | #11 |
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Re: Rejuvenating condensers
Lovely Julie, I like mad units too!
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11th Jul 2017, 8:45 pm | #12 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: Rejuvenating condensers
Thought you might, seeing your 32nHz frequency for the Sun
I've probably mentioned this before, but the kinetic energy imparted by a ten-ton truck stopping from 60 mph is scarily close to 1kWh. (60 * 1609.344 metres in 3600 sec. = 26.8224 m/s.; 0.5 * 10000 * 26.8224 * 26.8224 = 3597205.709 J. 1 kWh. = 1000J/s. for 3600s. = 3600000J.)
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11th Jul 2017, 10:10 pm | #13 |
Dekatron
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Re: Rejuvenating condensers
Speaking of green rectangular tin things; were these condensers oil filled in the 1930's? What record of continence/incontinence do they have please?
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11th Jul 2017, 10:34 pm | #14 |
Dekatron
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Re: Rejuvenating condensers
General consensus from previous threads is leakage may be caused by chemical decomposition in the oiled paper as the failure occurs just as commonly in well sealed capacitors. It would still be interesting to see if this works although not wildly practical. I may have some 1930's paper caps in tin somewhere that I have not yet pulled apart.
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11th Jul 2017, 10:48 pm | #15 | |
Octode
Join Date: Jul 2004
Location: Evesham, Worcestershire, UK.
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Re: Rejuvenating condensers
Quote:
greg. |
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12th Jul 2017, 10:39 am | #16 |
Octode
Join Date: Jul 2011
Location: Leicester, Leics. UK.
Posts: 1,685
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Re: Rejuvenating condensers
In my limited experience the green ones - or possibly grey - were usually wax filled, TCC, plus brown bakelite Dublier but there were certainly oil filled caps by the 40's in military sets, BC312 etc. Oil said to be rather toxic. They can leak.
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12th Jul 2017, 1:31 pm | #17 |
Heptode
Join Date: Jul 2012
Location: Daylesford, Victoria, Australia
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Re: Rejuvenating condensers
Paper exposed to air slowly carbonises at room temperature. If that contributes to the leakiness of waxed paper caps, it's not reversible.
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12th Jul 2017, 3:20 pm | #18 |
Dekatron
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Re: Rejuvenating condensers
Forum member GMB has done some similar research:http://www.vintage-radio.net/forum/s...ad.php?t=48730
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12th Jul 2017, 8:08 pm | #19 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
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Re: Rejuvenating condensers
The one I was mindful of is inside an early Avometer, it is a TCC in green, 2 1/4" x 2" x 5/8".
There was a stripe of a slightly oily deposit on the inside of the glass and I wondered if it derived from this component. I am not brave enough to test it in-situ as I don't think it has seen any action for a very long time! I also doubt I would be confident enough to try and reanimate it if it failed to hold charge. |
9th Aug 2017, 12:05 pm | #20 |
Heptode
Join Date: Jul 2012
Location: Daylesford, Victoria, Australia
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Re: Rejuvenating condensers
Last weekend I found nearly half a kilo of assorted unused wax paper capacitors (Ducon and UCC) at a garage sale, so I've been experimenting with the simmer in paraffin wax method. It works very well, but it takes around three hours to fix medium sized capacitors. These capacitors have wax-coated cardboard tube cases plugged at the ends with plastic. I'm using a mixture of paraffin and brown model making wax for resealing. I think the modelling wax is mostly carnauba, and it acts to reduce the brittleness of the paraffin.
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