Dead component replacement

Hi EEEEs (Experts Exchange Electronics Engineers),

I just turned the house power off and back on and found that my answering machine won't go back on.  It's an Audioline TAM838.  I thought I'd see if I could spot any dead looking components, and sure enough, there's a burnt area on the circuit board.  So if it's not too hard, I might try to fix it.  (Probably not worth my time, but could be interesting.)

Attached are long-distance and close-up photos of the insides.

Correct me if I'm wrong, but it looks to me as if the big crimson component has exploded and leaked onto the 2 resistors (covering one completely and another partially).

You can't see it in the picture, but the crimson component has this written on the burnt side:
    474K
    250V

Q1. Would you agree that the crimson component is most likely dead?

Q2. Is it likely that any other components have died as a result?  (Just trying to calculate funeral expenses, here.)

Q3. Can someone give me a description of that crimson component?  (A web search shows me it's probably a polyester film capacitor, but how can I tell what the capacitance is, etc?  Do I need a capacitance meter or should it be written on it somewhere?)

Q4. Do we have enough info for me to buy a replacement?  If not, how can I get enough?

Q5. Can you see any likely replacement candidates, here:
    http://newzealand.rs-online.com/web/c/passive-components/capacitors/polyester-film-capacitors/?sra=p
(The above link takes you directly to polyester film capacitors, in case that's what we need.)

Q6. Would you expect that the black & white 470uF 16V electrolytic(?) capacitor (top-right of close-up photo) is also dead?  I see it has some brown stuff on top of it, and maybe on the white phone-line connector cover next to it.

My electronics experience is not very good, but I do have a basic multimeter (no capacitance mode), if that helps.

Thanks.
tel2
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tel2Asked:
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rindiCommented:
To me the capacitor looks still OK. Usually it would be electrolytic caps that explode, leak etc. But it is hard to tell from the photo (maybe other viewing angles could help, or if you do some desoldering so the complete part can be seen on it's own).

But just below that cap it looks as if there is/was a diode, and that looks like it has died. Whether the resistor next to it is also gone is hard to say.

The problem, if a part has blown and you can't read the values, measuring them won't work, as those values would only be good with a working device.

I think your best option would be if you could find a schematic diagram of your device, or open an identical working one so you could read the markings on the still good parts.
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Emmanuel AdebayoGlobal Windows Infrastructure Engineer - ConsultantCommented:
Hi,

I would suggest that you should not bother to repair this for the following reason

1.Some other components might be affected but not showed as burnt
2.Trying to repair this does not worth your time, time to look/source for the burnt components, time in soldering the components together, power that you will used for powering your soldering iron etc
3.The cost of getting the components might be higher.

I would suggest just go to your local market or search on ebay, amazon to get the spare and you can just replace the whole PSU.

Just a token from me.

Regards
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Dave BaldwinFixer of ProblemsCommented:
I think you will probably find a burned or separated trace on the other side of the circuit board.  There is probably a blown fuse or resistor used as a fuse.  I think the brown stuff came from the orange cap.

This cap http://newzealand.rs-online.com/web/p/polyester-film-capacitors/7554677/ appears to be the correct value.

http://www.trademe.co.nz/ seems to have these come up for sale fairly often in the last year.
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Gary CaseRetiredCommented:
This almost certainly has a "fried" trace on the motherboard -- either under it or (if it's multi-layer) IN it.    Not a very good candidate for repair => especially considering this model is fairly frequently available on trademe (as noted above) ... and seems to sell for not much over $20 (Aus).
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nobusCommented:
Q1 yes, but likely it's not the only one; that is located on the AC side of the power supply, so from seeing it, i would suspect some rectifier diodes are gone bad also

Q2 : see above
Q3 : these are it's values :  474K -  250V
Q4: that info is enough; but make sure it has the Voltage range, 250 V
Q5: none fit the voltage requirement
Q6: difficult to say for sure- if in doubt, replace it (it does not cost much)
check if the top of the electrolytics are FLAT, not bulging
see:c
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tel2Author Commented:
Thanks to all of you for your comments/suggestions so far.  Points well taken.

Re my Q3, what is this "474K" a measure of?  Capacitance?  Surely it could not be 474KF, so what is it?
If 474K about capacitance, then how can I tell the capacitance value?

Thanks.
tel2
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Gary CaseRetiredCommented:
K is the code for a 10% tolerance ... so that's a 470uF capacitor +/- 10%
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nobusCommented:
i would assume it is a 470k = 0,470 microFarad for the orange one
i would expect a 250 V type to be much larger
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Dave BaldwinFixer of ProblemsCommented:
474 = 470,000 picofarads / .47 microfarads.
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tel2Author Commented:
Thanks again guys.

Hi Dave,
a) Are you trying to imply that the "K" indicates thousands in this case, and is not about tolerance?
b) Why picofarads?  Is that the default unit for all caps or just for polyester film, or what?

Thanks.
tel2
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Gary CaseRetiredCommented:
The K isn't part of the capacitor's value ... it's the symbol for tolerance -- in this case it means it's a 10% tolerance unit.

The 470 is a measure of capacitance.
As I noted before, it's likely a 470uF, 10% capacitor.

r.e. the comments that indicate that's too high a value for it's size -- I don't think so.   Take a look at similar units:  http://www.ebay.com/itm/Capacitor-470uf-250v-Electrolytic-Aluminum-85-C-4-pcs-/161100155327?pt=LH_DefaultDomain_0&hash=item25825149bf
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tel2Author Commented:
Thanks Gary,

> r.e. the comments that indicate that's too high a value for it's size -- I don't think so.
What comments from whom are you refering to?  I can't find any such comments from anyone above?

Thanks.
tel2
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Gary CaseRetiredCommented:
Both nobus and DaveBaldwin suggested it was 0.470 uF

I don't agree.   It's fairly clear it's a 470uF, 250v, 10% capacitor :-)

Nevertheless, I wouldn't suggest trying to fix this board (as I noted earlier).
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Dave BaldwinFixer of ProblemsCommented:
Almost all plastic and ceramic capacitors are marked in picofarads with a two-digit value followed by the number of zeros to be added.  It has been this way for at least the last 50 years.

http://www.mikesarcade.com/arcade/images/capcode.gif
http://en.wikipedia.org/wiki/Types_of_capacitor#Markings
http://www.elecraft.com/Apps/caps.htm
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Gary CaseRetiredCommented:
I had a brain lapse =>  I knew that, but was off by a factor of 10^3 !!

My "mental math" when I said "... K is the code for a 10% tolerance ... so that's a 470uF capacitor +/- 10% "  was 47 x 10^4 = 470,000 ... but I was thinking the relationship between pf and uf was 10^3 when it's actually 10^6

... and when nobus said "... i would expect a 250 V type to be much larger ..."  (which is, of course, not true)  I simply focused on that instead of re-thinking my math :-)
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nobusCommented:
i agree a modern one "could " have the same size factor, but the older ones are bigger imo.
tx for the backing up, Dave
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tel2Author Commented:
Hi again guys,

Thanks for sorting out that wee point of contention.  Good to have agreement on that now.

I unsoldered the capacitor, diode and resistor, and you can see them attached (after some cleaning), and the circuit board before and after I cleaned the gunk off it.  All 3 components appear to be in tact...visually.

* The resistor tested OK at 2.18K ohms (approx as expected for 3 red bands).

* The diode reads infinite resistance in one direction (as expected), but in the other direction I get different ohms readings depending on the scale on my digital multimeter!  I.e.:
    - On the 200 ohm range it reads infinite.  Fine so far - obviously more than 200 ohms.
    - On the 2000 ohm range it reads 816.
    - On the 200K ohm range it reads 3.57 (i.e. 3,570 ohms).
    - On the 20K ohm range it reads 28.1 (i.e. 28,100 ohms).
    - On the 20M ohm range it reads 2.07 (i.e. 2,070,000 ohms).
Q7. Is this normal?  Why does this happen?  Is the diode likely to be faulty?  (No such thing happens when I test the resistor so I don't think it's my multimeter).

* I can't test the capacitor properly (no proper capacitor test equipment), but on my multimeter I can see it charging, etc (then again when I swap the terminals), but I can see this only on the 20M resistance range.

Q8. Where do you think all that gunk could have come from?  The right-hand leg of the capacitor, perhaps?

The other side of the circuit board looks fine to me.

Q9. Just out of interest, why do you think the manufacurer used a 250V capacitor for this application?  The output of the (external) power adaptor (not shown in the photos, but its model "9VDC300"), takes 240V AC 50Hz input, but gives 9V DC 300mA output.

PS: Yes, I'm aware this is most likely not with fixing, but I'm learning stuff.

Thanks again.
tel2
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Dave BaldwinFixer of ProblemsCommented:
Q7.  That is a normal diode reading.  You would get more consistent result with a diode setting on your multimeter.

Q8.  I think the cap is bad and that's where the gunk came from.  Although... the 470UF 16V cap, the black one with white markings, has brown gunk on the circuit board by it.  You should pull it and see if there is more gunk there.  It is actually a much more likely point of failure.

Q9.  The manufacturer already had an excess of them.
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tel2Author Commented:
Thanks for the fast and helpful response, Dave!

Good spotting about the black & white cap!  As mentioned in Q6, I had noticed the gunk on top of that cap, but I didn't notice the gunk on the circuit board before, so it seems your eyesight from a few thousand miles away is better than mine from a here.

I've now disconnected that cap, and the gunk trail goes from its top down to the circuit board (and the circuit board is lower than the components in this device), so I assume it's been leaking from the top.

It passed the basic resistance test I did for it before, but that doesn't mean much.

Apart from the 470uF & 16V, it also says "18 degrees C", "+/-20%" and "VENT" on the side, and the brand looks like "truth"??? I think.  Would this suffice as a replacement:
http://www.ebay.com/itm/10-x-470uF-16V-105C-Radial-Electrolytic-Capacitor-8x11-/250851988762?pt=LH_DefaultDomain_0&hash=item3a67f1951a
(That would leave me with just 9 spares!)

I'd still probably need to replace the polyester film cap, of course.
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Dave BaldwinFixer of ProblemsCommented:
That cap on eBay looks fine as long as it fits.
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tel2Author Commented:
Thanks Dave,

The dimensions look the same (8x11mm).

Regarding the crimson cap:
- How do we know whether it's polyester film or ceramic or other?
- If polyester film, are there cheaper alternatives for this application?
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Dave BaldwinFixer of ProblemsCommented:
Well, it looks like plastic polyester and it does not look like ceramic.  If you're sure there's no high voltage there, you can use one with a lower voltage rating which is usually cheaper.
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tel2Author Commented:
Well, I don't see how (or why) there would be high voltage, considering the output voltage of the (external) power supply is 9V DC, Dave.  That being the case, do I just have to allow for 9V max or could it be higher?

Also, is "plastic polyester" the same as "polyester film"?  Google's not helping much...yet.

Thanks again.
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Dave BaldwinFixer of ProblemsCommented:
It's all plastic, don't worry about it.  And you can't get one of them plastic caps rated for only 9 volts so don't worry about that either.  It will be at least 50V.  Switching power supplies can generate high voltages from low voltages.  That is unlikely here but possible.  I did see a wirewound inductor in the pictures.
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Dave BaldwinFixer of ProblemsCommented:
All you need to know: http://en.wikipedia.org/wiki/Film_capacitor  And polyester is also know as Mylar which is trademarked by DuPont.
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tel2Author Commented:
Great!
Thanks Dave.
Feel free to take the rest of the day (or is it night?) off.  You deserve it.
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nobusCommented:
>>  , I don't see how (or why) there would be high voltage  <<  it is probably a filter cap, to filter spikes - and these can be high
if you have an electronics parts shop around, i wuld take the board and parts to it, and ask for replacements
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tel2Author Commented:
OK, nobus.  Thanks.

Would it be reasonable to guess that if 2 caps have already leaked, others are likely to do the same in the reasonably near future?  This device is probably 10 years old.
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Dave BaldwinFixer of ProblemsCommented:
There really isn't any correlation between caps leaking and not.  Especially since they are made in different ways.  It is most likely that the electrolytic leaked and the plastic cap wicked some of the brown stuff into it's plastic cover.  I have stuff here that I built 25 years ago from parts that were surplus 20 years before that and they don't have any problems.
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tel2Author Commented:
Thanks Dave.
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nobusCommented:
in most cases, the leaking is caused either by high temperature,
But if you doubt, the best way is to replace all electrolytics with new ones (they don't cost much)
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tel2Author Commented:
Thanks nobus.

> in most cases, the leaking is caused either by high temperature,
Either by high temperature or what?

Thanks.
tel2
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nobusCommented:
by high temps around.
many motherboards had this problem with the caps around the CPU heatsink
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tel2Author Commented:
Thanks to all of you for your input with this.

I hope the points work out reasonably fair.  Sorry, nobus, I think I should have increased the default points for your "accepted solution".  However, your last 2 posts were probably only worth 30 points total, so hopefully that compensates somewhat.  I marked that post as the "accepted solution" because it was the most comprehensive single post which worked through all my questions.

Anyway, if I find time I might try to fix this someday, armed with the education you've given me.

BTW, can anyone recommend a cheap device for properly testing capacitors?  Something on ebay, perhaps?  Hopefully under US$30.  Or do proper capacitance test devices cost more than that?  I've seen some multimeters there that claim to test capacitors, like this one:
www.ebay.com/itm/20mA-20A-AC-Current-Capacitor-Voltmeter-Ohmmeter-HFE-Multitester-Yellow-Black-/290952661495?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item43be2149f7
And here's a dedicated capacitance testor:
www.ebay.com/itm/A6013L-LCD-Capacitance-Capacitor-Meter-Tester-Multimeter-20mF-To-200pF-/161083029896?pt=LH_DefaultDomain_0&hash=item25814bf988

Any comments about the cheap ones above, and do you expect the dedicated one somehow do a more thorough test than the multimeter one?  Obviously it has more ranges.

Thanks again.
tel2
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Dave BaldwinFixer of ProblemsCommented:
I have a BK 815 Component Tester that I have used for years that I like.  Looks like the price hasn't changed much,  http://www.ebay.com/itm/BK-Precision-815-Component-Tester-/190895827392?pt=LH_DefaultDomain_0&hash=item2c724729c0
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nobusCommented:
if yourrefer with "your last 2 posts were probably only worth 30 points total" then i must say i'll never get many points, since i keep my answers as short as possible (ASAP) since i'm spending now each day already 3 Hours at least helping here

have fun...

regarding the capacitor tester, you should know that there is no really good, complete tester, since in order to be able to measure  them properly, it should be tested at the working voltage - which varies from less than 1 V to maybe over 1000 V

so what they do is do a basic measurement of the capacitance only
you can also test the internal resistance of a capaciitor  http://shop.anatekcorp.com/products/component-analyzers/blue-ring-tester-assembly/?back=products
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tel2Author Commented:
Hi nobus,

Thanks for that extra info.

> if yourrefer with "your last 2 posts were probably only worth 30 points total" then i must say i'll never get many points, since i keep my answers as short as possible (ASAP) since i'm spending now each day already 3 Hours at least helping here

True, but I'm talking about relative to other posts, including some of yours.  There are only 500 points to go around a lot of posts, and I think you got a reasonable proportion of the total.

BTW, when I asked this:
   >> in most cases, the leaking is caused either by high temperature,
    >Either by high temperature or what?

I was trying to get you to give me the other part of the either/or sentence.  I'm not sure you understood that, coz I still don't know whether there was one.

Anyway, thanks for all your advice.
tel2
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nobusCommented:
could be anything really (so i left that off, leaving the either) : manufacturing faults, voltage spikes etc... not really something that gives you a clear indication   - so i deleted that part
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tel2Author Commented:
OK.
tel2
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