Bulging 1950s dual electrolytic - what would you do? - UK Vintage Radio Repair and Restoration Discussion Forum

Nickthedentist · 12th Dec 2014, 1:03 pm

Hi everyone,

I've been playing with an untouched but unloved Ekco A277 which I picked up at RWB. It's a big, FM-only set with dual speakers from the mid-50s. I'd hoped it hadn't seen mains for a long time as it was still fitted with a 5A 2-pin plug.

After cleaning off all the dust and general grime from the chassis, I noticed that the dual 50uF can has a pronounced bulge in the bottom bung, centred on the vent between the terminals.

OTOH, it re-formed well with a leakage current of just over 1mA per section on my reformer.

In operation, it doesn't get even warm, and there's no audible hum.

Why do you think it looks like that? Did someone apply mains after a long period of dormancy?

What do you think its prospects are? Is it likely to fail dangerously?

What would you do?

Nick

paulsherwin · 12th Dec 2014, 2:24 pm

Personally I would replace it, but I'm less keen on reforming old electrolytics than many people.

I don't think it will fail dangerously though. The cabinet is likely to contain any flying debris.

I restored one of these a while ago - a good performer and a handsome set, though in a rather gloomy 1950s British sort of way. The speaker fabric is synthetic so can be carefully cleaned with foaming cleaner.

Duke_Nukem · 12th Dec 2014, 2:27 pm

Two answers really. First it appears to be working just fine and I'm guessing it is bulged but not actually leaking. In which case leave it.

On the other hand, if you end up listening to it whilst not comfortable that a bang is pending at any time then replace it.

I had a Ferguson (IIRC) television with a hugely bulging cap that also pointed nicely at the CRT neck. I wouldn't have connected a 1.5v battery to it let alone mains but apparently it worked just fine.

TTFN,
Jon

kalee20 · 12th Dec 2014, 2:28 pm

Any chance of a photo?

I have seen many electrolytics with a slight bulge, still in service, still doing their jobs. I can count the number of HT smoothing capacitors I have replaced with the fingers of one hand.

Electrolytics generally fail through going high resistance (drying out) so humwill increase, possibly accompanied by instability. After some years of none-use, reforming may be prudent, but provided that leakage current stabilises at a low value, risk of explosion is negligible. Any tendency to do so would manifest itself in the first hour of use.

HamishBoxer · 12th Dec 2014, 2:29 pm

I think I would not risk leaving it in either.Remember my tale of a 950 series Thorn TV that had a failure when new and split the cabinet.

richrussell · 12th Dec 2014, 2:46 pm

I'd probably leave it, then if it starts to hum restuff it with modern capacitors. As said above - if it's performing well, then it's probably in no immediate danger of failing, and should it go with a bang you won't need to wonder what it is that failed.

G6Tanuki · 12th Dec 2014, 4:09 pm

My instinct would be to replace it. Then you'll know it's good-to-go for the next 50 years.

Chances are, your existing one will last for many years - but the First law of Technical Malevolence dictates that in reality it will explode catastrophically half an hour after you've reassembled the radio in its case.

Capacitors are cheap. "Fix once, fix for good" makes sense.

12th Dec 2014, 4:14 pm

Quote:

I'm less keen on reforming old electrolytics than many people

I am with Paul here, modern caps. are so cheap and reliable (and small so they fit) it isn't worth hoping the old one will keep going. Worst case the rectifier valve and mains transformer go tits up, it's not worth it. I spent £80 on a new (rewound by a forum member, bloomin' good job) mains transformer for my A22 (well worth it) because the HT cap. had failed.

fetteler · 12th Dec 2014, 4:34 pm

Hi Nick,

Re-stuff it.

Here's the logic: I don't think you'd be asking the question if you were 100% happy and, of course, it'll need doing one day (probably sooner rather than later) so why not do it now whilst you have the chance and then as has already been said, you can sit back and enjoy listening without a care!

Steve.

Techman · 12th Dec 2014, 5:44 pm

Speaking for myself, I wouldn't worry about it.

I've had a lot of electrolytics with a 'bump' in the end cap and they're still working years later.

For me, in most cases, there's only two tests. The first is - is it getting warm after a short time? The second is - is there more than normal mains hum? If the answer is no to both, then leave it alone, but just check the temperature over the first hour or so of operation - the can should stay virtually cold.

I like to see as many of the original components as possible still working and doing their job.

This 're-stuffing' seems on the face of it to work ok and I think it's worth doing when a part has failed and replacement is the only answer and the 'look' needs to be preserved. But, the design voltage and temperature rating of a capacitor is surely for when operated in an un-enclosed space with free air flow around the component, and not sealed up in the can of the old capacitor. There's probably nothing to worry about in reality, but these components are not designed to be sealed up inside another component - or are they?

G6Tanuki · 12th Dec 2014, 6:12 pm

Quote:

Originally Posted by Techman

This 're-stuffing' seems on the face of it to work ok and I think it's worth doing when a part has failed and replacement is the only answer and the 'look' needs to be preserved. But, the design voltage and temperature rating of a capacitor is surely for when operated in an un-enclosed space with free air flow around the component, and not sealed up in the can of the old capacitor. There's probably nothing to worry about in reality, but these components are not designed to be sealed up inside another component - or are they?

Modern electrolytics are rated for 85 or 105 Centigrade operating-temperature. In modern 'solid-state' equipment it's quite common for those sorts of temperatures to be reached.

Older consumer-spec electrolytics rarely quoted operating-temperatures. I have no problems with using modern 105-centigrade electrolytics in valve equipment [but I don't go to the bother of 're-stuffing' - in the very rare instance cosmetics are a concern I'll wire the new components under the chassis and leave the old 'can' to fill the hole]

GMB · 12th Dec 2014, 9:05 pm

So long as the bulging bits are only the rubber covers to the vents then it's not too bad as this represents a tiny amount of electrolyte loss. Anything else bulging and it must be scrapped since it is probably distortion of the guts that ultimately ignites the gases inside.

I try to reuse the old parts if they test OK. I have replaced older parts with modern ones only to find that the ESR of the modern part is actually worse than the original!

HamishBoxer · 12th Dec 2014, 9:48 pm

Restuff with the good quality BVWS caps or equal.

marconi_pete · 12th Dec 2014, 11:52 pm

In this situation I'd also restuff the can with new caps. Not worth taking any chances.

Thanks,
Peter

Maarten · 15th Dec 2014, 2:49 am

The temperature printed on modern electrolytics is not just an 'operating temperature', it's also the temperature for which the life expectancy is given in the datasheet. Often somewhere between 1000 and 5000 hours, which is quite short. This will roughly double for every 10 degrees lower, so a 105 degree electrolytic specified for 1000 hours will last 8000 hours (just under a year of continuous operation) at 85 degrees.

Therefore, taking the operating temperature into consideration is important.

Nickthedentist · 19th Dec 2014, 8:14 pm

Thanks for all the advice and comments, chaps, which I've read with interest.

Here are a couple of pictures.

It's still in place, still cool as a cucumber, and still doing great service, but I have to say that the thought of it damaging the rectifier and/or transformer (and possibly my nerves!) is making me think I might change it for one of the BVWS "F&T" ones.

Does anyone know the dimensions of these? The pics in the ad in the Bulletin are rather ambiguous regarding the 50/50uF size, and at £7.00, I don't want to get it wrong. An American reseller seems to suggest 1 3/8".

And can one discard the blue plastic sleeve on these, to make it look more authentic, bearing in mind that the common negative connection does not need to be isolated from chassis?

Website here, but I can't find these on it: http://www.ftcap.de/index.php/electr...apacitors.html

Nick.

mark pirate · 19th Dec 2014, 8:30 pm

I would leave it in situ, I would only restuff or replace it if it was electrically leaky or getting warm.
It is not uncommon to have a little bulge there, it is just the vent outlet.

Mark

yesnaby · 19th Dec 2014, 9:07 pm

Nick,

You could go for the 'Dreamliner solution': put it in a metal box with a vent to the outside. (Only joking!)

Michael

Nuvistor · 19th Dec 2014, 9:56 pm

I wanted a couple of the 50+50 when I was at Golborne but they were out of stock and did not know when they would get any more, they could be in stock again but they were not hopeful. I bought a couple along with one or two other items from JustRadio. If you wish I can dig one from Just Radio out and measure it.
Frank

12th Dec 2014, 1:03 pm	#1
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Bulging 1950s dual electrolytic - what would you do? Hi everyone, I've been playing with an untouched but unloved Ekco A277 which I picked up at RWB. It's a big, FM-only set with dual speakers from the mid-50s. I'd hoped it hadn't seen mains for a long time as it was still fitted with a 5A 2-pin plug. After cleaning off all the dust and general grime from the chassis, I noticed that the dual 50uF can has a pronounced bulge in the bottom bung, centred on the vent between the terminals. OTOH, it re-formed well with a leakage current of just over 1mA per section on my reformer. In operation, it doesn't get even warm, and there's no audible hum. Why do you think it looks like that? Did someone apply mains after a long period of dormancy? What do you think its prospects are? Is it likely to fail dangerously? What would you do? Nick Last edited by Nickthedentist; 12th Dec 2014 at 1:09 pm.

12th Dec 2014, 2:24 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Bulging 1950s dual electrolytic - what would you do? Personally I would replace it, but I'm less keen on reforming old electrolytics than many people. I don't think it will fail dangerously though. The cabinet is likely to contain any flying debris. I restored one of these a while ago - a good performer and a handsome set, though in a rather gloomy 1950s British sort of way. The speaker fabric is synthetic so can be carefully cleaned with foaming cleaner.

12th Dec 2014, 2:27 pm	#3
Duke_Nukem Octode Join Date: Jan 2003 Location: Birmingham, West Midlands, UK. Posts: 1,268	Re: Bulging 1950s dual electrolytic - what would you do? Two answers really. First it appears to be working just fine and I'm guessing it is bulged but not actually leaking. In which case leave it. On the other hand, if you end up listening to it whilst not comfortable that a bang is pending at any time then replace it. I had a Ferguson (IIRC) television with a hugely bulging cap that also pointed nicely at the CRT neck. I wouldn't have connected a 1.5v battery to it let alone mains but apparently it worked just fine. TTFN, Jon

12th Dec 2014, 2:28 pm	#4
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: Bulging 1950s dual electrolytic - what would you do? Any chance of a photo? I have seen many electrolytics with a slight bulge, still in service, still doing their jobs. I can count the number of HT smoothing capacitors I have replaced with the fingers of one hand. Electrolytics generally fail through going high resistance (drying out) so humwill increase, possibly accompanied by instability. After some years of none-use, reforming may be prudent, but provided that leakage current stabilises at a low value, risk of explosion is negligible. Any tendency to do so would manifest itself in the first hour of use.

12th Dec 2014, 2:29 pm	#5
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: Bulging 1950s dual electrolytic - what would you do? I think I would not risk leaving it in either.Remember my tale of a 950 series Thorn TV that had a failure when new and split the cabinet. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

12th Dec 2014, 2:46 pm	#6
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Re: Bulging 1950s dual electrolytic - what would you do? I'd probably leave it, then if it starts to hum restuff it with modern capacitors. As said above - if it's performing well, then it's probably in no immediate danger of failing, and should it go with a bang you won't need to wonder what it is that failed.

12th Dec 2014, 4:09 pm	#7
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Bulging 1950s dual electrolytic - what would you do? My instinct would be to replace it. Then you'll know it's good-to-go for the next 50 years. Chances are, your existing one will last for many years - but the First law of Technical Malevolence dictates that in reality it will explode catastrophically half an hour after you've reassembled the radio in its case. Capacitors are cheap. "Fix once, fix for good" makes sense.

12th Dec 2014, 4:34 pm	#9
fetteler Octode Join Date: Jul 2011 Location: Staffordshire Moorlands, UK. Posts: 1,477	Re: Bulging 1950s dual electrolytic - what would you do? Hi Nick, Re-stuff it. Here's the logic: I don't think you'd be asking the question if you were 100% happy and, of course, it'll need doing one day (probably sooner rather than later) so why not do it now whilst you have the chance and then as has already been said, you can sit back and enjoy listening without a care! Steve. __________________ Those who lack imagination cannot imagine what is lacking...

12th Dec 2014, 5:44 pm	#10
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Bulging 1950s dual electrolytic - what would you do? Speaking for myself, I wouldn't worry about it. I've had a lot of electrolytics with a 'bump' in the end cap and they're still working years later. For me, in most cases, there's only two tests. The first is - is it getting warm after a short time? The second is - is there more than normal mains hum? If the answer is no to both, then leave it alone, but just check the temperature over the first hour or so of operation - the can should stay virtually cold. I like to see as many of the original components as possible still working and doing their job. This 're-stuffing' seems on the face of it to work ok and I think it's worth doing when a part has failed and replacement is the only answer and the 'look' needs to be preserved. But, the design voltage and temperature rating of a capacitor is surely for when operated in an un-enclosed space with free air flow around the component, and not sealed up in the can of the old capacitor. There's probably nothing to worry about in reality, but these components are not designed to be sealed up inside another component - or are they?

12th Dec 2014, 9:05 pm	#12
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,095	Re: Bulging 1950s dual electrolytic - what would you do? So long as the bulging bits are only the rubber covers to the vents then it's not too bad as this represents a tiny amount of electrolyte loss. Anything else bulging and it must be scrapped since it is probably distortion of the guts that ultimately ignites the gases inside. I try to reuse the old parts if they test OK. I have replaced older parts with modern ones only to find that the ESR of the modern part is actually worse than the original!

12th Dec 2014, 9:48 pm	#13
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: Bulging 1950s dual electrolytic - what would you do? Restuff with the good quality BVWS caps or equal. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

12th Dec 2014, 11:52 pm	#14
marconi_pete Hexode Join Date: Mar 2012 Location: London, UK. Posts: 347	Re: Bulging 1950s dual electrolytic - what would you do? In this situation I'd also restuff the can with new caps. Not worth taking any chances. Thanks, Peter

15th Dec 2014, 2:49 am	#15
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Bulging 1950s dual electrolytic - what would you do? The temperature printed on modern electrolytics is not just an 'operating temperature', it's also the temperature for which the life expectancy is given in the datasheet. Often somewhere between 1000 and 5000 hours, which is quite short. This will roughly double for every 10 degrees lower, so a 105 degree electrolytic specified for 1000 hours will last 8000 hours (just under a year of continuous operation) at 85 degrees. Therefore, taking the operating temperature into consideration is important.

19th Dec 2014, 8:14 pm	#16
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Bulging 1950s dual electrolytic - what would you do? Thanks for all the advice and comments, chaps, which I've read with interest. Here are a couple of pictures. It's still in place, still cool as a cucumber, and still doing great service, but I have to say that the thought of it damaging the rectifier and/or transformer (and possibly my nerves!) is making me think I might change it for one of the BVWS "F&T" ones. Does anyone know the dimensions of these? The pics in the ad in the Bulletin are rather ambiguous regarding the 50/50uF size, and at £7.00, I don't want to get it wrong. An American reseller seems to suggest 1 3/8". And can one discard the blue plastic sleeve on these, to make it look more authentic, bearing in mind that the common negative connection does not need to be isolated from chassis? Website here, but I can't find these on it: http://www.ftcap.de/index.php/electr...apacitors.html Nick. Attached Thumbnails Last edited by Nickthedentist; 19th Dec 2014 at 8:27 pm.

19th Dec 2014, 8:30 pm	#17
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Bulging 1950s dual electrolytic - what would you do? I would leave it in situ, I would only restuff or replace it if it was electrically leaky or getting warm. It is not uncommon to have a little bulge there, it is just the vent outlet. Mark

19th Dec 2014, 9:07 pm	#18
yesnaby Octode Join Date: Jul 2005 Location: Newport, Gwent, UK. Posts: 1,623	Re: Bulging 1950s dual electrolytic - what would you do? Nick, You could go for the 'Dreamliner solution': put it in a metal box with a vent to the outside. (Only joking!) Michael

19th Dec 2014, 9:56 pm	#19
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Bulging 1950s dual electrolytic - what would you do? I wanted a couple of the 50+50 when I was at Golborne but they were out of stock and did not know when they would get any more, they could be in stock again but they were not hopeful. I bought a couple along with one or two other items from JustRadio. If you wish I can dig one from Just Radio out and measure it. Frank