Why is this Cap getting hot and bulging?

[sandyK]

If the sound quality is slowly "cycling", but the voltage is still correct, give the new capacitor around 48 hours to fully form. A 105C capacitor would be better at that location though. Many of the larger capacity low ESR capacitors often have a pronounced SQ cycle, and usually settle down to optimum after 48 hours or more of use,

 

[jean-paul]

Using 105 degree caps in a hot environment is pretty self explanatory. I would also replace all small caps for decent 105 degree branded types that are known for good quality.

I promised not to use the name again but it starts with a P...

 

[mace1337]

..anasonic?

I agree, Pana FC/FM are excellent caps.

 

[AndrewT]

move the cap to a cold location !

 

[J.R.Freeman]

Hi Jim,

thank you for your reply.

I've determined the cap is getting warm from the tube, and also the two heatsinks in the rear. I can only hold my finger on it for 5 seconds, so it is pretty hot. I've had the amp running now for 4 hours, and the cap is barely warm.

Yes, the psu came with the amp... it looks like a laptop brick psu.

I agree with you, I think the stock psu is crap, and it is going into current limiting.

I just ordered a heavy duty regulated switching psu on ebay. 24v at 3amps. the stock one is 2amps, but I'm guessing it is very over rated.

Here is a rear view of the amp, you can see the two black heat sinks.

View attachment 203847

Anyhow, I think my problem is a combination of things. Too much heat around the stock cap, running too close to the rated 25v, and a weak stock psu.

I think I'm going to get a 6800uf 35v cap, and install it on top of the case, like I did with the 10,000uf cap.

Hi Matt,

Oh ok interesting - thanks for the pic. The cap is actually mounted above the board huh? Is that glass or plastic in between?

About the power supply - you might want to try contacting the manufacturer before buying a new supply (I know this might be too late). They might be able to better help you trouble shoot.

Jim

 

[mattjk]

Yes, cap is mounted about, but the amp just sounds bad now... I need to put a smaller cap back in.

I got the new 3amp PSU. Works great (starts up without going into overload protection) but I reversed the polarity the first couple times and I blew out the USB power section. I traced it down to a bad transistor, which I ordered.

 

[mastodon]

yeah, I haven't been using it.

I have a 10,000uf 100v chemicon cap. Would that be ok to use? How would it affect the sound?

It should be ok to use it, but it won't fit as a snap-in replacement, as your new cap is considerably bigger (physically).

If and how it will affect the sound, that depends on where it's located. I take it it's located right after the external power supply input. In that case, the impact on sound quality will be limited if you compare it to the original cap if it were in working order. If, with the original cap in non-working order, you experience any hiss or hum originating from the power supply, then installing the new cap will/might get rid of that. If the external power supply already has good filtering and provides a stable and well-buffered voltage, then you probably won't notice any differences at all. Some people claim that they hear distinct differences between different brands/types of audio caps, but in a situation like yours, I'm pretty sure that I wouldn't be able to spot the difference.

 

[mace1337]

It should be ok to use it, but it won't fit as a snap-in replacement, as your new cap is considerably bigger (physically).

If and how it will affect the sound, that depends on where it's located. I take it it's located right after the external power supply input. In that case, the impact on sound quality will be limited if you compare it to the original cap if it were in working order. If, with the original cap in non-working order, you experience any hiss or hum originating from the power supply, then installing the new cap will/might get rid of that. If the external power supply already has good filtering and provides a stable and well-buffered voltage, then you probably won't notice any differences at all. Some people claim that they hear distinct differences between different brands/types of audio caps, but in a situation like yours, I'm pretty sure that I wouldn't be able to spot the difference.

Have you.... actually read the topic? He already mounted the new cap.

 

[Mr. Triatic]

once now and then it happens that the outer plastic of a capacitor gets twisted around 180º, last week i popped a cheap asian "crapacitor" that was obviously wrongly polarized.

 

[semi932]

Aside from the cap itself, check to see if there are any hairline cracks in the board in that area.
If a trace has blown or is nicked it can cause this to happen.

 

[J.R.Freeman]

Yes, cap is mounted about, but the amp just sounds bad now... I need to put a smaller cap back in.

I got the new 3amp PSU. Works great (starts up without going into overload protection) but I reversed the polarity the first couple times and I blew out the USB power section. I traced it down to a bad transistor, which I ordered.

Hey Matt,

I'm sorry to hear about the troubles. Is the amplifier working at the moment? Are you able to post a schematic (assuming it is not copyright protected) so that we might help you to find parts that could have been damaged by the polarity event?

Jim

 

[mattjk]

don't have a schematic, sorry.

I believe the cap was a fake. it had no markings of polarity and did not have the usual "K" stamp on the top, like other rubycon caps.

 

[cbdb]

Was there no warranty?

 

[js091526]

Rubycon BXA is a series in 160~450VDC and 6.8~220uF capacitors. So it might be a fake one.

 

[JMFahey]

it had no markings of polarity

Then how did you know it was inserted the right or wrong way?

 

[kevinkr]

Guys, really? This thread has been dead for almost 4 yrs... lol

 

[JMFahey]

Oh !!
NOW I understand why this guy doesn't answer