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Help to identify capacitor

H

harry

Experienced Member
Joined
Oct 19, 2007
Messages
310
Location
United Kingdom
I have recently had a bit of bad luck,whilst leaving my victor vicky powered on for some time, it suddenly decided to emit a nasty smell and finally die on me.
having opened up the case , I have found a blown capacitor on the floppy controller board, as it is now blown completely apart I have no values to read, to obtain a replacement. Close to this C20, is C19, same size same looking, but its values are a little confusing to me. It looks unlikely I can obtain any schematics, so I am going to try and find a replacement as C19. It reads +t310, K20%,3r3uf 15v. It measures aprox 3/16" dia.coloured black, and is axial leads, one end positive, position shows positive end on the board, as if electrolitic. Can anyone throw some light on what would be a suitable replacement, as searches throw up nothing similar. thanks..... Harry
 

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Hmm, from the traces I'd say it's just a power supply bypass which isn't really critical; probably between 10 and 100 uf. I'd say there's a good chance that it took out something upstream; hope I'm wrong. Measure the voltage.
 
Hi
It says it is a 3.3 micro farad at 15 volts and is a 20% part. What
is the problem? And yes, it is an electrolytic.
Dwight
 
Dwight Elvey said:
Hi
It says it is a 3.3 micro farad at 15 volts and is a 20% part. What
is the problem? And yes, it is an electrolytic.
Dwight
Click to expand...
Huh? Oh, the other one; right! I thought you must have pretty good eyes to read that off the charred lump ;-) Could be a small axial tantalum though, not that it matters.

Still a good chance that something else was damaged. Check the voltage.
 
hi, thanks for replies to this, why use 3r3uf instead of printing 3.3uf. the problem for me, but not to those who know, was finding a replacement, with the same markings, so Dwight the problem was no info on what 3r3 meant, just try google search for that cap..... nothing,, so its good to use this forum for help !
I hope nothing else has been destroyed, when this happened, but I will take your advice and check things out. why do these components blow, is it just old age? , damp storage,? or what? can anything be done I wonder to avoid this happening, or is it just a matter of time before the next component fails.....



thanks...... Harry
 
That's the convention .. you could easily miss seeing the dot.

The fact that it blew apart tells you that it was across the power supply for smoothing and therefore the exact value is very unlikely to be important. Don't worry too much about it, parts get old and they eventually fail.
 
paul said:
That's the convention .. you could easily miss seeing the dot.

The fact that it blew apart tells you that it was across the power supply for smoothing and therefore the exact value is very unlikely to be important. Don't worry too much about it, parts get old and they eventually fail.
Click to expand...
-------
Agreed; it's not critical, and they do sometimes just fail when they get old, especially tantalums. But the fact that the system died kinda suggests that the excessive current drawn while it was shorting and smoking overloaded the PS; any blown fuses anywhere by any chance?
 
Hi
The r is a european standard. If had said 3k3, it would have been 3,300
instead. Since it blew with a bang, it is most likely a supply rail bypass.
If that is so, the value is not critical. In fact the unit might work fine
without it. If the 3.3 is hard to find, 4.7 or 5 uf might be easier.
They generally fail with age. The ones in the cans with the black
plastic covers are generally electrolytics. The ones in the axial cans
that have a clear plastic are usually tantalums. Other tantalums look
like a blob of colored epoxy on the ends of two radial leads.
Do consider that it might have damaged the supply or regulators.
You should test the supply by it self to make sure it is ok as well.
Some switchers need a minimal load. a 6 volt interior automotive light
works fine for most small supplies. For a larger supply, a brake light
is better.
Dwight
 
I've gotten to the point where if a cap on a board goes BANG! and the system doesn't go down, I make a note of it and keep working. Old caps do fail suddenly. If they're bypass or decoupling, no big deal.

Far worse are the caps that fail by leaking all over the PCB--or the polystyrene ones that catch on fire...
 
Hi, thanks for all the replies, and now things seem a lot clearer, I have sent the psu to someone who will check its outputs and replace all the caps, while he has it. so that should be ok, Thanks Dwight for your suggestions for alternative
caps, I am confident I will find something suitable now. I checked for any fuses blown initially but all was ok, as soon as things are rebuilt I will let you know the outcome. Meanwhile I'll continue my quest to understand more about electronics and components! Thats whats so great about learning , being able to ask those who know! great stuff ......... Harry




( why get lost in the fog if there is someone to guide you!! )
 
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