Bulging Caps

[POLKAT 10+ year member]

I just received a used old-school Directed 1100d from ebay. I decided to take a quick look at the guts and I noticed that the 2 largest capacitors are bulging at the top. The bottom one is fully expanded while the one above it is about half way there.

http://i38.photobucket.com/albums/e131/cncsutor/amp/amp005.jpg

http://i38.photobucket.com/albums/e131/cncsutor/amp/amp002.jpg

The marks on the top of the caps are where they were pressing against the cover of the amp.

I know that blowing a cap can be very dangerous..especially ones as large as these. Do you think it would be worth it to try and get the caps replaced by an electronics repair shop?

Click to read more...

 

[POLKAT 10+ year member]

Wow lol, I guess it was a harder question than I thought. :stuck:

The amp does power up and work fine btw.....

This is a shameless bump before bed with hopes that someone will put their two cents in. //content.invisioncic.com/y282845/emoticons/zzzzz.gif.06fa1eabe00c8b872d7e814474c9b95c.gif

 

[Beat_Dominator 5,000+ posts]

That's not a good sign, If you aren't afraid to replace them I would do it.

 

[POLKAT 10+ year member]

I have very little experience with a soldering iron besides soldering wire to terminals.

Would it be feaseable for me to buy 2 replacement caps and do it myself?

 

[helotaxi 5,000+ posts]

You'll have to take the board out of the heatsink to get to the solder points. Make sure you have thermal paste to put between the power supply and output stage transistors and the heatsink when you reassemble it. Make sure that you don't overheat the circuit board with the soldering iron. Other than that, replacing the caps should be pretty straightforward.

 

[NhustlaR 10+ year member]

why do you need thermal paste for the heat sinks?

 

[NhustlaR 10+ year member]

pressure alone wont do the trick?

 

[helotaxi 5,000+ posts]

pressure alone wont do the trick?

Not optimally, no. You really need something to conduct the heat from the device to the heatsink unless the mating surfaces of both the device and the sink are perfectly smooth (and they never are). Some amps use a film between the two but most use thermal paste.

 

[Beat_Dominator 5,000+ posts]

I have very little experience with a soldering iron besides soldering wire to terminals.Would it be feaseable for me to buy 2 replacement caps and do it myself?

I have decent soldering expirence but nothing with circuit boards and I just replaced ~10 capacitors on my home subwoofer amplifier I got from eBay.

De-Soldering braid is a gift from God. If you feel like you can have patience and put it all back together properly you'd be fine //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Rawb]

De-Soldering braid is a gift from God. If you feel like you can have patience and put it all back together properly you'd be fine //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

De-Soldering Braid - FTW x2x3x4x5....

it really isnt hard to take a couple caps off a baord and replace them... if need be find a old cd player or stereo or somethin electronic that you dont need with a board... take it apart and use that as a test dummy to take off some caps.... itll help ya.... alsoa 3rd arm can be a great use while doing this to take the caps off the board with a free hand rather then holding it... 40w iron a set of needle nose pliars and braid is all ya need } : >

 

[nVRuckus 5,000+ posts]

pressure alone wont do the trick?

using something like artic silver 3 will insure that there are no gaps between the 2 pieces of metal which can cause problems later on.

 

[POLKAT 10+ year member]

I have some Arctic Silver laying around so that wont be a problem.

One thing I am worried about is since those are fairly large capacitors, what would be the best way for me to discharge them so I don't get jolted when I start messing around with them?

 

[Beat_Dominator 5,000+ posts]

Arc them over with a screw driver with a plastic handle.....I doubt they'll have a charge in them anyway.

 

[Bolognablake 10+ year member]

I have decent soldering expirence but nothing with circuit boards and I just replaced ~10 capacitors on my home subwoofer amplifier I got from eBay.
De-Soldering braid is a gift from God. If you feel like you can have patience and put it all back together properly you'd be fine //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Pretty much my first experience when repairing an old PPI amp. The first one took a little while, but you'll get the hang of it.

I'd also use this opportunity to invest in a good soldering iron. Because it can take forever to soak up the solder with a cheap one.

 

[Blazin_Jason 10+ year member]

I like to use a solder sucker as well. Basically it's a tool that you heat up the solder, and then sucks up the solder. Use that with solder braid and you will be fine. Also since you know that those caps are starting to go, you should replace them. You wouldn't want them to leak and eat the traces/parts in the surrounding area. Try and treat the cancer before it spreads. =)