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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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10th Jun 2021, 11:12 am | #1 |
Diode
Join Date: May 2021
Location: New Forest, Hampshire, UK.
Posts: 3
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Question about capacitors
I would like to ask anyone with any knowledge about electrolytic capacitors what might cause what appears to be verdigris on capacitor leads and spread along circuit tracks?
The strange thing being most of them are 47uf. So I have gone through the circuit board replacing all the affected components because this just can't be right. The board is in a Major 788 CB radio, PTBM133A4X. It works well, and in a good condition yet these capacitors are of some concern. Anyone with knowledge of this would be very helpful. Thanks |
10th Jun 2021, 1:59 pm | #2 |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,498
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Re: Question about capacitors
But is it emanating from the electros, or is it perhaps a chemical reaction left over from the soldering process? From the pictures there does not appear to be goo on the cap. seals.
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10th Jun 2021, 3:10 pm | #3 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
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Re: Question about capacitors
Interesting situation. It looks to me there has been 'capillary action' along the leads of the capacitors. This can be incredibly invasive despite what appears to be an air tight seal. I have experienced many times when restoring vintage equipment.
That is the main reason for the failure of the 'lock fit' transistors, detector diodes and unexplainable loss of vacuum in B7G and B9A valves that have been in storage, not under ideal conditions for a few decades. Just how the damp/impurities/rot/mould creep along the wires occurs under such sealed conditions is a mystery but it does including glass to metal seals. Just a suggestion and there may be another explanation. John. |
12th Jun 2021, 7:51 am | #4 |
Diode
Join Date: May 2021
Location: New Forest, Hampshire, UK.
Posts: 3
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Re: Question about capacitors
All interesting replies, thanks. Other than this the radio is in great condition for its age. If it ain't broke.......
|}Natalie |
12th Jun 2021, 8:51 am | #5 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Question about capacitors
I bought a brand new-old-stock Tektronix FET probe, with power supply. It came with 110V transformer tapping, so I took the lid off the power supply to change the transformer taps.
There were two axial electrolytics, in smoothing duty, very high quality, and which were leaking. A few decades old. What I think had happened is that Tek used a defluxing agent which compromised the rubber seal of the capacitors. This is not unknown. Removed them, cleaned the goo off the board, and found axial RIFA electrolytics of about the same value and physical size, problem sorted. Craig |
12th Jun 2021, 9:50 am | #6 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Question about capacitors
Electrolytic caps are not a sealed component and I have a box of large power supply
caps in which I had stored some metal capacitor clips - I assume the steel is BZP or other plating. Some months later I noted a strong smell when the box was opened and the bright plated clips were heavily tarnished, some had actually rusted. Storage, temperature and humidity have effects - your Major must be around 40 years old and the cost of replacing the caps with new 105 degree types is negligible. |
12th Jun 2021, 1:32 pm | #7 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 992
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Re: Question about capacitors
I received some new Panasonic FC caps a few months ago - some of which displayed a similar verdigris, albeit to a lesser extent, directly from the supplier.
The supplier replaced them without question, and even followed up with their Q/C dept., who supplied the following statement, apparently from Panasonic. Make of it as you will - I still had reservations, so binned the caps in question. I should add, the supplier in this case was Mouser (USA), and the customer service provided by the Mouser (UK) office was simply outstanding, particularly for a small hobbyist customer. Alan |
21st Jun 2021, 8:06 am | #8 |
Triode
Join Date: Jul 2020
Location: Angeles City, Philippines.
Posts: 27
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Re: Question about capacitors
yep those folks at mouser bend over backwards to treat the customer right. i ordered some diodes and even tho the bag had the correct description as the invoice it was obvious that a nichicon upw capacitor was not a diode. they accepted the claim and sent the correct parts at no charge. no arguments either. and thats 1/2 way round the planet to mansfield,texas too.
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24th Jun 2021, 4:40 am | #9 |
Heptode
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 663
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Re: Question about capacitors
There was a period of time when the electrolyte would leak out- defective electrolyte chemistry.
This was exceptionally prevalent in the capacitors that one of the TV mfgrs. used in the last few years of CRT TV sets. The electrolyte would also smell like rotten fish when it was heated. Highly corrosive to PC traces. Would eat them up, and eat through the leads of the capacitors. |
24th Jun 2021, 8:05 am | #10 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Question about capacitors
The rotten fish smell was present in my HP 5328A counter/timer. Main smoothing caps. Fortunately caught them before they had damaged the board.
Replacement cured the problem. Craig |
24th Jun 2021, 12:22 pm | #11 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Question about capacitors
The rotten fish smell reminds me of the widespread leakage of the surface mount electrolytics used in early 1990s Canon camcorders. It was a horrible problem to deal with. In a number of cases the PCB copper foil was corroded. I think Sony had a similar problem with some of their consumer equipment.
Regards, Symon |