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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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15th Jul 2021, 5:45 pm | #1 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
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Wima 5/35 capacitor
I am checking around the AF/IF board on a Redifon R550A and come across a Wima 5/35 capacitor leaking it is marked plus and minus what are the values?
Thanks, Chris. |
15th Jul 2021, 6:03 pm | #2 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,203
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Re: Wima 5/35 capacitor
Most likely 5uF 35V. Where is it in the circuit?
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15th Jul 2021, 6:18 pm | #3 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 714
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Re: Wima 5/35 capacitor
Hi Martin. I can't find a service manual for it so I am looking at a manual for an R551 which states C168. So it's a 5uf 35 volt electrolytic it's only small.
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15th Jul 2021, 9:10 pm | #4 |
Moderator
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Re: Wima 5/35 capacitor
How about a picture of the cap?
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15th Jul 2021, 9:12 pm | #5 |
Dekatron
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Location: W.Butterwick, near Doncaster UK.
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Re: Wima 5/35 capacitor
4.7uF 35 V DC will replace , 105 C if possible.
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15th Jul 2021, 9:50 pm | #6 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
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Re: Wima 5/35 capacitor
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15th Jul 2021, 10:46 pm | #7 |
Moderator
Join Date: Mar 2012
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Re: Wima 5/35 capacitor
Straight forward aluminium electrolytics. Go for one of the reputable Japanese makes. Panasonic, Nichicon, Nippon Chemi-con or Rubycon. Be wary of fakes trying to look like those names.
David
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15th Jul 2021, 11:12 pm | #8 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 714
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Re: Wima 5/35 capacitor
Got it thanks for your help guys.
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23rd Jul 2021, 2:54 pm | #9 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 714
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Re: Wima 5/35 capacitor
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23rd Jul 2021, 3:04 pm | #10 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,010
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Re: Wima 5/35 capacitor
Looks like a Tantalum to me.
They were used extensively in the 70s and 80s in places where you needed high capacitance and low ESR in a small space [e.g. for decoupling]. They have a high failure-rate when old, going POP! and emitting some impressive smoke/orange flames! These days conventional low-ESR aluminium electrolytics are the recommended replacement. |
23rd Jul 2021, 3:16 pm | #11 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 714
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Re: Wima 5/35 capacitor
Yes this one has gone pop ! Its off the 1.4 mhz oscillator board the service manual only shows the top of the board not the bottom it has brown red brown stripes on it so I am stumped as to the value .
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23rd Jul 2021, 4:55 pm | #12 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
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Re: Wima 5/35 capacitor
I thought they were highly reliable, which was why NASA used them extensively in space, as they don't leak or degrade and have a lot in a small package. I thought they went POP when overloaded, which is apparently common, expense meant lots of equipment didn't have suitably derated specifications - a 10V capacitor decoupling a 9.5V rail, for example.
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23rd Jul 2021, 5:13 pm | #13 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Wima 5/35 capacitor
The supposedly-reliable ones were 'wet' Tantalum always encased in a metal tube. They have turned-out to have a less-than-spectacular extended-service life [1970s-1990s 'Clansman' military radios use loads of them - and they fail!]
As to the particular value of the failed one, I can't help alas: the ones I've come across either have the value printed on them, or they have two different colours to the resin encapsulation along with a spot at the junction of the 2 colours (shades of the old tip-body-spot resistor colour code?). |
24th Jul 2021, 12:09 am | #14 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,350
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Re: Wima 5/35 capacitor
G6T, sorry, Body-Tip-Spot, not tip-body-spot.
I think they were ALL like that when I first played about! Les. |
24th Jul 2021, 9:14 am | #15 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,999
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Re: Wima 5/35 capacitor
Quote:
Going back to terrestrial matters, tantalum beads only go pop when used in power supply decoupling. The data sheet guidance was to use a 6V capacitor on a 5V line and a 16V one on a 15V line. And 6V/16V rated tants were the ones available for that reason. And I used them in my first job in the early 1980's in exactly that way. The mechanism for failure seems to be their lack of ability to absorb ripple current. They last for maybe three or four decades and then pow. If connected to a supply with no crowbar, they can explode leaving just the leads sticking up, or ignite and burn clear through the board. When used in signal circuits, in coupling or decoupling applications, tant beads seem to be entirely reliable. Craig |
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24th Jul 2021, 9:37 am | #16 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
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Re: Wima 5/35 capacitor
Quote:
Peter |
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24th Jul 2021, 9:50 am | #17 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 714
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Re: Wima 5/35 capacitor
So how do you determine the value they are more like golf balls than beads .
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24th Jul 2021, 10:36 am | #18 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,327
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Re: Wima 5/35 capacitor
You’ll have to work out what it’s connected to and then find those parts on the circuit diagram.
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24th Jul 2021, 11:23 am | #19 |
Nonode
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
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Re: Wima 5/35 capacitor
The maximum value doesn't matter, just needs to be large enough to decouple or remove hum. This photo is 47µ 25V. Replace with a modern electrolytic, as suggested above
What guarantees an explosion was a high inrush current, as anyone connecting one straight across a supply line soon found out
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24th Jul 2021, 11:33 am | #20 |
Nonode
Join Date: Dec 2012
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Re: Wima 5/35 capacitor
Your Tant looks like 1µ, as in 1,000 nF
If anyone wants a few bags of NOS tantalums, just let me know...
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