Bugera 333xl-212 cap problem

[harrisxr650]

Hey guys. i (maybe) have a problem with the filtering caps(?) on my amp. I've opened today the chassis to clean it a bit from dust and i noticed that 2 of the large caps have formed a bubble in the top. The amp is working as it should be but i think its better to replace them to make sure it wont blow in the middle of a rehearsal or, worst, a gig. Maybe do a full recap?
The problem is that the (ready to blown) caps values are 680uf 350v and cant find anything within the EU with that capacitance value (tried banzai and tube-town)
Note that if its necessary to replace them i would like to get better caps than these ones (cant remember the brand but they seems like cheep ones).
any tip will be appreciated.
btw i'm aware the electroshock dangers while working inside a tube amp and i know how to proper discharge a large cap, i know better that i do have to be extra careful even if i have discharge them.

[52 Bill]

...i noticed that 2 of the large caps have formed a bubble in the top. The amp is working as it should...

Try pressing down on the bubbled cap and see if it will move in. Often the plastic cap will bubble out but the top of the metal case is perfectly fine underneath.

[harrisxr650]

tried already and seems solid...didnt apply much force though a little more than a stompbox switch needs when pressed with hand.

[olddawg]

I do not have the experience with tube amps that many on this board have, but I was a high end bench tech for many years. I wouldn't worry about it. I have seen domed caps like that last for decades. It's a filter cap. If it isn't leaking I wouldn't worry too much about it. It is an inexpensive Chinese component and may not have a vent hole or the vent may be covered with glue from the manufacturing process. If it starts to fail it will probably be gradually and you will hear some hum. You could probably replace it with a 1000uf if you still think it needs to be done if you can't locate the proper replacement. I would just keep using the amp. Of course any amp can have a catastrophic failure. If you use tube amps regularly you should always have a backup available anyway.

[Jazz P Bass]

Here is the stock inventory at Farnell UK.
They have other EU outlets.
Electrolytic Capacitor | Aluminium Electrolytic Capacitors | Farnell United Kingdom | Results

[harrisxr650]

thanks everyone...i think its best to change it just to be sure it wont mess up anything else.
thanks again

[Enzo]

If that is how you feel about the part, then what is there to lose? Take a razor blade or something and slit the plastic sleeve around the cap so as to free the plastic disc covering the end. Remove the disc. Is the cap under it domed or not. There is absolutely no point in just throwing new caps at it if only the plastic is warped. I also see it all the time, the caps are usually fine underneath.

[harrisxr650]

Thanks Enzo i'll check i either way i ordered some caps just to have them spare in case they need to be replaced.
Anyway thanks everyone will post as soon as i strip the plastic cover and check the cap

[harrisxr650]

So..haven't check the cap yet will do it tomorrow ( had to clean up the house a bit :P ), but i've put an order at Farnell which i havent pull the trigger yet..but there are a couple of things i wanted to ask about caps... The ones that are installed are rated 680uf 350v@105c, i know that getting a cap with higher voltage rating ( lets say 400-450v) should be better but (forgive me if i'm wrong or being noobish) what about temperature? is there any difference if a same capacitance, same or higher voltage but at 85c is installed in place?
i did a little research about power supply filtering on the internet and saw many posts about "low esr, high ripple electrolytic capacitors" and how crucial it is but none determines how much low esr and high ripple is good enough? Or isnt that crucial as many claim it is? So which value is good for esr and which for ripple current if it is? And how esr is determined since in most cases nothing is written on the cap datasheet? And last when esr value is labeled "mOhm" should i take that as microOhm or millyOhm or megaOhm? (damn it i always get confused with that... )
Btw i did choose these caps to order dont know which one is better or if it doesnt matter, any opinions?

EETHC2G681EA - PANASONIC - CAPACITOR, 680UF, 400V | Farnell United Kingdom
400VXH680MEFCSN35X45 - RUBYCON - CAPACITOR, 680UF, 400V, 20%, 35X45MM | Farnell United Kingdom

again thanks for the help and sorry for the silly questions i post
Harris

[harrisxr650]

So i removed the plastic disk from the top of the cap and the and it is a bit (its a little but it is) domed. So i guess i have to change those caps. Any suggestions on my previous post will be appreciated.
thanks again