UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

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.

Closed Thread
 
Thread Tools
Old 2nd Dec 2017, 9:18 pm   #41
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,751
Default Re: Electrolytic capacitor fails after 1 hour in service!

You keep saying they're a reputable brand.

Reputable manufacturers know exactly what their reputation is worth, and their prices carry a premium because of it.

Reputable manufacturers know what damage counterfeits do to their reputation, and faulty units that get stolen. They very much want to track down and destroy the sources of these parts. It is to the advantage of the rest of us if you contact the manufacturer and some action is taken to get the duds off the market. Please contact them.

Reputable manufacturers also know that occasional units fail, and they handle these events in a way which preserves their reputation for standing behind their products. They are also likely to be interested in understanding the cause of the failure and this improves their parts, so please contact them.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 2nd Dec 2017, 10:27 pm   #42
Argus25
Octode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 1,659
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by kalee20 View Post
but known internal rejects, but a dishonest employee has intercepted them en route to the skip to flog them and make some easy money.
That is an interesting mechanism of how this could happen, if they made a mislabeled batch at the factory, say 16V caps labelled as 63V, or reverse polarity and put them in a dumpster out the back, they would look pretty attractive to anyone, not necessarily an employee. Then the person selling them might not have known there was an issue in the first place.

It is a big deal in the aviation industry how to dispose of faulty parts, often they end up getting recycled & sold as refurbished. Sometimes they mutilate them before dumping. There was a story about a helicopter blade(these things are worth 100's of thousands of $) being mutilated with multiple holes drilled in it. Someone found it, filled the holes with Bondofil, repainted it with a masterful black gloss coat and on sold it.

At least with axial electros the polarity is self evident due to the rubber seal. But radial ones it relies on the plastic cover being put on and labelled correctly.

Check the physical size of the caps against others, if its a mislabeled 16V one it should be physically smaller than a 63V one of the same capacity.

One thing I found recently with radial electros, if they have leaked electrolyte in the past (which can sometime not be easily optically visible) if meter probes are placed on the rubber base, 2 or 3mm apart, they conduct because the electroltye is on the rubber's surface.

I recently repaired a video monitor where a film of invisible electrolyte had coated the board in an area of a few square inches and corrupted the function of some high impedance circuits in a color processor circuit.The board also had a matt looking conformal coating which I think was microscopically porous. Standard pcb cleaner had no effect at all, in the end warm water managed to remove it. Another electrolytic nightmare.
Argus25 is offline  
Old 2nd Dec 2017, 10:56 pm   #43
astral highway
Nonode
 
astral highway's Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 2,661
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Radio Wrangler View Post
Please contact them.

Reputable manufacturers also know that occasional units fail, and they handle these events in a way which preserves their reputation for standing behind their products. They are also likely to be interested in understanding the cause of the failure and this improves their parts, so please contact them.

David
You've convinced me. I'll do it...
Quote:
Originally Posted by kalee20 View Post

Please do!

You say they are a reputable brand, well, in that case if they are mislabelled they'll want to know. If someone 'out there' is making counterfeits, again they'll want to know.

It's even possible that they may be genuine, but known internal rejects, but a dishonest employee has intercepted them en route to the skip to flog them and make some easy money. Again, they'll want to know.
Ahah, yes, again, there seems to be a raft of support growing here. I know what to do now.
__________________
Al
astral highway is offline  
Old 2nd Dec 2017, 10:57 pm   #44
cmjones01
Octode
 
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 1,804
Default Re: Electrolytic capacitor fails after 1 hour in service!

It sounds too me like the capacitor shouldn't have failed, but the way to find out what's going on is to replace with another one the same and see if it fails again. If it does, then either there's something odd about the circuit which is damaging the capacitor, or you've got a bad batch of capacitors. Then you can try one of the same ratings but from a different supplier or manufacturer and see if that helps.

Decoupling a gate driver chip is hardly arduous duty for a big electrolytic like that, and you'd know pretty quickly if its ripple current rating was being exceeded: it would get really, really hot. In the case of ripple current, it's the heat that does the damage. That's why higher voltage rated capacitors tend to have higher ripple current ratings for the same capacitance. They're in bigger cases so they dissipate the heat better.

Chris
__________________
What's going on in the workshop? http://martin-jones.com/
cmjones01 is offline  
Old 2nd Dec 2017, 11:00 pm   #45
astral highway
Nonode
 
astral highway's Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 2,661
Default Re: Electrolytic capacitor fails after 1 hour in service!

[QUOTE=Argus25;996322]
Quote:
Originally Posted by kalee20 View Post

That is an interesting mechanism of how this could happen, if they made a mislabeled batch at the factory, say 16V caps labelled as 63V, or reverse polarity and put them in a dumpster out the back, they would look pretty attractive to anyone, not necessarily an employee. Then the person selling them might not have known there was an issue in the first place.
...

At least with axial electros the polarity is self evident due to the rubber seal. But radial ones it relies on the plastic cover being put on and labelled correctly.

Check the physical size of the caps against others, if its a mislabeled 16V one it should be physically smaller than a 63V one of the same capacity.
Some interesting insights there, Hugo. That helicopter wing scam is jaw-dropping and criminal! It's a more sinister version of the old saying, 'Where there's muck, there's brass.'
__________________
Al
astral highway is offline  
Old 3rd Dec 2017, 12:34 am   #46
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,751
Default Re: Electrolytic capacitor fails after 1 hour in service!

When a blade comes off a helicopter, you can't autorotate to a nice landing, and ejector seats aren't a common fitment...

This is a high probability of killing people. Then there are all the fake drugs. What if something you need to stay alive gets replaced with fake labelled aspirin?

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 3rd Dec 2017, 2:10 am   #47
Argus25
Octode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 1,659
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Radio Wrangler View Post
Then there are all the fake drugs. What if something you need to stay alive gets replaced with fake labelled aspirin?
David
What about the fake parts in car Airbags and the massive recalls and costs there.

It seems practically everything in our world has been faked; currency, artworks, watches, DVD's, nearly every electronic part, drugs, nothing is spared, perhaps only cathode ray tubes. I haven't seen a fake one yet, but I wish somebody would try then we might get some spare parts !

Ps: the helicopter that got that refurbished rotor was shown on TV lifting a heavy object (I think a crashed plane out of bushland) and amazingly despite the holes in the main rotor, it didn't break, it was discovered later.

I've attached a pdf of a brief Fake Part story I had a while back.
Attached Files
File Type: pdf THE CASE OF THE COUNTERFEIT 2N5543.pdf (389.9 KB, 49 views)

Last edited by Argus25; 3rd Dec 2017 at 2:26 am. Reason: add attachment
Argus25 is offline  
Old 3rd Dec 2017, 6:20 pm   #48
astral highway
Nonode
 
astral highway's Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 2,661
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Argus25 View Post


The problem remains though in vintage transistorized equipment where the common capacitances can be over 30 to 50uF, often into the 100's or 1000's of microfarads and there is no room to fit other capacitors. In this case my practice is now to fit Tantalums, preferably mil grade for lower range values and I remain forced into an electrolytics for the high values, but I always strive for the higher temp rated parts.
I might follow suit there, Hugo. I have found a source of some axial types to mil spec M39003, and will use 1uF values rated 75V as just part of the decoupling design to replace what failed.

I'm also on the hunt for bigger values; there seem to be a lot of ex-Soviet bloc types that are NOS or pulls from military equipment but the unit cost is very high indeed...
__________________
Al

Last edited by astral highway; 3rd Dec 2017 at 6:31 pm.
astral highway is offline  
Old 3rd Dec 2017, 6:37 pm   #49
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 10,751
Default Re: Electrolytic capacitor fails after 1 hour in service!

That may be where you're going wrong. The risk of fake components is lowest from authorised distributors who have regular turnover and direct interaction with the real manufacturer. Grey market things get cheaper and riskier.

Real mil-spec stuff appears affordably on the surplus market, and there's this chief petty officer Pertwee chap whose prices are quite reasonable.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 3rd Dec 2017, 7:16 pm   #50
astral highway
Nonode
 
astral highway's Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 2,661
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Radio Wrangler View Post

Real mil-spec stuff appears affordably on the surplus market, and there's this chief petty officer Pertwee chap whose prices are quite reasonable.

Ah, intriguing, David! Who is chief petty officer Pertwee?
__________________
Al
astral highway is offline  
Old 3rd Dec 2017, 10:45 pm   #51
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 4,577
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Radio Wrangler View Post
That may be where you're going wrong. The risk of fake components is lowest from authorised distributors who have regular turnover and direct interaction with the real manufacturer.
It's lowest, but not zero. Occasionally counterfeit parts do emerge from an authorised distributor. What happens is, somebody buys a load of genuine parts, then a few months later asks if they will buy them back, quoting the C of C number (obviously with a restocking fee). But what they actually do is send a load of counterfeit parts. Then they sell the genuine parts on the 'grey market'.

I'm actually involved right now dealing with 1N825A diodes, bought from a big distributor in the US, which are in a different package (DO35) than ordered and certified (DO7). I'm pretty confident that the diodes are genuine, but the paper trail is not quite what it should be - and our customer is not impressed because the different package, with different internal construction, invalidates qualification tests done some years ago.
kalee20 is offline  
Old 3rd Dec 2017, 11:39 pm   #52
'LIVEWIRE?'
Dekatron
 
'LIVEWIRE?''s Avatar
 
Join Date: Mar 2006
Location: N.W. Oxfordshire(Chipping Norton)
Posts: 6,149
Default Re: Electrolytic capacitor fails after 1 hour in service!

CPO Pertwee (played by John Pertwee, btw), as us 'olduns' will remember, was a character in 'The Navy Lark', a radio comedy set on and around 'HMS Troutbridge'. He was in Charge of the stores in the series, and various items would 'dissapear' and be sold by said CPO Pertwee on the black market. If challenged he would deny all knowledge of such deals.
'LIVEWIRE?' is offline  
Old 3rd Dec 2017, 11:43 pm   #53
Argus25
Octode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 1,659
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by kalee20 View Post
....which are in a different package (DO35) than ordered and certified (DO7). .
Often a clue to a fake is a non standard or different package. One major methodology for fakers is simple parts substitution and re-label (most fakers wouldn't be able to make a semiconductor device themselves even if you gave them a block of Galena and a cats whisker and a Dymo label machine)

One good one I saw recently was a mosfet with a higher RDSon than the original part. The fakers didn't know that in the circuit is was in, it had little heat sinking because the design always had it off or fully enhanced carrying 20A. So the fake part melted, but probably in other circuits they would have gotten away with it.

This is how they get away with it a lot of the time of course, they are aided by the good Engineers who build with conservative design rules and the parts slip through unnoticed and appear to work ok.
Argus25 is offline  
Old 4th Dec 2017, 1:35 pm   #54
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 4,577
Default Re: Electrolytic capacitor fails after 1 hour in service!

Quote:
Originally Posted by Argus25 View Post
Quote:
Originally Posted by kalee20 View Post
....which are in a different package (DO35) than ordered and certified (DO7). .
Often a clue to a fake is a non standard or different package.
I agree - but in this case I reckon the diodes are genuine. The manufacturer (Microsemi) used to make them in DO7 (glass package, internally soldered)and in DO35 (smaller glass package, brazed construction). They differentiated with a part number suffix. They changed the location of manufacture to a facility which had DO35 capability but not DO7, 10+ years ago. At the time, they sent out a circular informing the world of this (which I now have).

Unfortunately, someone made a blunder on the Web site, indicating the DO35 suffix as obsolete, and DO7 as current. To most users it is immaterial, probably why the error was never picked up. To us and our customer, it is important. I caught it and queried it. Unfortunately the error crept as far as the Certificate of Conformance we received, which indicates that even genuine parts from a genuine manufacturer can be misrepresented.

Microsemi have confirmed from a photo I sent, that the diodes, sold as DO7, are DO35 - and although they have not yet received a return, they haven't shouted that they are bogus. But they're amending their on-line data.

So Al's capacitor - he's doing all of us a favour by alerting the manufacturer.
kalee20 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:48 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.