Burnt out mains capacitor - Page 2

> Alan Dicey wrote:
>
>> The biggest danger from larger capacitors is explosive decomposition
>> from putting AC across them. Larger capacitors are polarised and can
>> only be connected across a load where the DC component is larger than
>> the AC ripple. Going negative will result in a fountain of hot paste
>> spitting out of a safety vent in the lid of the can.
>
> Ah yes, the yellow stinky stuff. ;-) DH not me - it stains too, much
> like ferric chloride.

> Chrisy wrote:
>
>> Thank you so much Alan for the link and the great advice.
>> Imagine how much the shop would have charged us to replace one cap.
>> Probably about $70AU (approx £35) would be a fair guess.
>
> The shop would charge for the labour involved in removing and replacing
> the circuit board and the component. Maybe 30 minutes to one hour.
>
>> Dick Smith want $0.95 for the cap plus $9.95 for P&H, so you've saved us
>> around $60! You've really helped us out a lot.
>
> The postage seems a lot compared with the component price. Maybe its
> worth skimming Dick Smith's catalog for anything else you might need -
> tools, solder, adhesives, CD/DVD-ROMs, cases, that sort of thing.
>
> In the UK I am lucky that there is a supplier that maintains a physical
> presence, real shops you can visit. Maplin Electronics has two shops
> within a 30-mile radius of here. Tandy/Radio Shack used to have a shop
> even closer, but they have closed down in the UK - however they still
> appear to be alive in Australia, so it may just be possible there is one
> close to you. Whether it is within AU$10.00 worth of petrol is a
> separate question :-)
>
> In Australia I expect that distances between towns are larger and useful
> shops less widely distributed. I can find other online suppliers,
> though, Jaycar, Altronics, Farnell Australia and RS Components
> Australia, should you need to shop around in the future.
>
>> I never realised how many amazing things capacitors are used for till I
>> started to look into it yesterday. You must really know your
>> electronics. It was the use of a comer instead of a full stop as a
>> point symbol (0,1uF) that confused me. I didn't know if it meant 0.1 or
>> 1 uF, but I guess 1 Farad must be quite a lot. Some of those larger
>> caps sound quite dangerous.
>
> The use of a comma for the decimal place is standard practice in
> continental Europe. Rifa is Swiss-based.
>
> Capacitors are charge storage devices, and large devices can store
> enough to give a startling shock. One Farad would be a large
> capacitance, and I've never seen a single device that large. In the few
> applications where they are necessary they are built up from banks of
> smaller devices.
>
> The biggest danger from larger capacitors is explosive decomposition
> from putting AC across them. Larger capacitors are polarised and can
> only be connected across a load where the DC component is larger than
> the AC ripple. Going negative will result in a fountain of hot paste
> spitting out of a safety vent in the lid of the can.
>
> Anything can be dangerous if handled carelessly.
>
>
>> Anyway, cheers for that Alan, it's very much appreciated.
>
> No problem. I assume that you or someone nearby is confident enough
> with a soldering iron to swap out the dead component.
>
> I'd be careful to check the machine for any other damaged components,
> resistors showing signs of overheating or capacitors with bulged cases.
> When I refurbished Kate's Elna, the root of the problem was a
> burned-out resistor, the capacitors had just aged and bulged from
> overheating. Metallised Paper capacitors are known to deteriorate with
> age. It may be worth replacing any other such devices on the board.
>
>

>
>
> Careful not to overheat the board while soldering or desoldering,
> especially if close to any active devices (transistors, integrated
> circuits - generally anything with three or more leads). Also, the
> printed circuit tracks can lift off the surface if overheated. A
> desoldering pump can be helpful.
>
>
> Out of interest, can you post pics of the board, showing the burned out
> component, if you have a digital camera?
>
>> And being and Aussie Sheila I guess I better say it just for a laugh.
>
> The UK. Same house as Kate :-)

> Chrisy wrote:
>> Husqvarna Optima 150
>> We have burnt out an AC capacitor in our old Husqvarna.
>> What we wanted to know is if it's alright to continue using it with the
>> cap removed, at least till we can find another one?
>
> I'd say probably not. This machine has electronic speed control, and
> this component could easily be part of the control circuit, not just a
> transient supressor.
>
> Having refurbished components on an Elna TSP Air Electronic circuit
> board (which required me to reverse-engineer the circuit diagram), I
> would say that it's not safe to assume that this capacitor is just a
> mains supressor
>> On the cap it says:
>> Front:
>
> I can translate some of these
>> RIFA
> Manufacturer, Evox Rifa
>
>> 40/085/56 GPC
> 40/085/56 - IEC Climatic category: 40°C, 85% rH, 56 days
>
>> PME 271M 610
>> CP9
> Manufacturers item code
>
>> Top:
>> 0,1uF@X
> 0.1 microFarads, the capacitance of the device.
> X - Classification of capacitor,international standard. Intended for
> use as interference suppressors across the power input. That doesn't
> mean that it can't be used for something else, of course.
>
>> Back:
>> fo=4,9MHz 250V~MP
> fo=4,9MHz - self-resonance frequency 4.9MHz
> 250V - 250 volt rated voltage
> MP - Metallised Paper, the construction materials
>
>> 565-1ALD2
>
>> There are some other symbols on the back that despite looking up special
>> symbols tables, I found no way of reproducing. But I think there is
>> more than enough information there anyway. (:
>
> These are likely to be the various standards markings indicating
> certifications and approvals the device complies with.
>
> The capacitor should look a lot like this one:
> https://www.wellgainelectronics.com/index.asp?PageAction=VIEWPROD&ProdID=2985
>
>
>
>> We couldn't find much in the way of caps in Australia so
>> would one of these do the trick? The direct link to the page is way too
>> long, so I had to use tinyURL to create a link, sorry.
>> This is the home page, just in case your wondering.
>> http://www.dse.com.au/cgi-bin/dse.storefront/
>> This is the tinyURL link to the high voltage capacitor page.
>> http://tinyurl.com/l2bh4n
>
> Your tinyurl isn't working for me.
> From the supplier you've chosen, I'd go for this component, which will
> replace your burned-out example
>

>
>
>

>
> Hay Alan.
> The cap arrived today, Adrian put it in, and it works like a charm!
> Thank you so very much for your able assistance.
>
> Maybe it's just a cheaper version, but the new one is a fair bit
> smaller, then again I guess 20 odd years is a long time in electronics.
>
> I took a few pics (as you asked) with my mobile, and as soon as I fire
> up my work laptop with the bluetooth card in, I will email them to you.
> Yours gratefully.
> Chrisy.

> Hi there.
> This looks like a great newsgroup.