Caps o buldgin'?

[Buddy]

I am going over my mark III component by component and found this little guy lookin a little too proud . Think its ready to pop . The amp is twenty yrs old this month .


http://i86.photobucket.com/albums/k85/gufefut/bulgie2.jpg

The '47uf on the bottom ( Little brown guy )

"nother view

http://i86.photobucket.com/albums/k85/gufefut/buldgie1.jpg

Could I be wrong ? Advice appre , apree, apree , welcome .

Thanks ,
B

 

[disassembled]

I say replace it. Snip the ends of the cap, pull the leads out, desolder the holes, fit new cap, solder in place, snip leads, be happy


A $5 part that can cause some nasty damage is worth replacing IMO. It doesn't look good but who knows it might have come like that from the factory.

I'd play it safe. Call Mesa, hoffman amps, etc for a replacement. Just make sure to go equal or high on the voltage rating and you'll be golden.

Greg

 

[Boogiebabies]

Those are bias supply caps and they are not bulging. Small elecrolytics bulge at the terminal ends, not in the middle. I would just leave them unless you see them oozing yellow goo from the ends.

 

[user 2126]

Like bb said now visualize:
1:

2:

 

[kdove]

by the way, replacements for my caps (picture #1) will be here Thursday.

 

[user 2126]

by the way, replacements for my caps (picture #1) will be here Thursday.

is it the 30uf 500v or the long 200uf 300v you are waiting for.

 

[Schmoog]

as usual, I agree with boogiebabies. with a couple caveats. your amp is important to you, so if you are uncomfortable with the caps like that, then change em. it cant hurt. but dont do it yourself, and don't change just one. at 20 years of age, the amp is going to be needing a cap job soon anyways, so your better off taking it to a tech and getting a total re-cap. it'll help your tone in ways you never thought possible. as far as brands go, in my personal experience there are only two: sprague and mallory. everything else is just hype

 

[kdove]

I'm just thankful that I visit this board and determined I needed new ones. For me good advice. My amp was losing volume yesterday ... it does this rarely. I decided to leave it unplugged until the new parts got here in a few days. Can you imagine how I'd feel if it popped a cap the day before the new parts arrived ... when they were almost 30 years old. :shock:

I'm replacing them all. 220uf/285v are F&T ... 30uf/500v are sprague

 

[Buddy]

The reason It concerned me is it has a slight convexity as compared to its twin ; the rubber terminal end has a ( and its shrink wrap also appears to be drawn with it .
2 things in my limited experience cause a electrolytic cap to fail explosively , higher than rated voltage applied to the cap and reversed polarity on the leads . I learned this working in a stereo shop in my younger days .
You take a 25v v cap , stick it to your victims toolbox lid ( bubble gum or sunroof sealer ) with a mercury switch and apply voltage in an inappropriate manner ....
For the last 9 years the amp has been relatively unplayed due to offspring care and an appalling amount of home renovation . I did make sure to turn it on at least 3 times a month for 5 -10 mins and play through it to hopefully "exercise" the caps . I just retubed it and have been playing it a lot more often and for longer periods . I'm sure some board member's sneeze out more boogie knowledge every morning than I have learned , but , I'd rather err on the side of caution .( One result of parenthood )
To properly replace all electrolytics , would one have to pull/loosen the circuit board ?
Sometimes a little knowledge is worse than none at all .
Thanks , B .

 

[Restless Rocks]

Hey Buddy that's a nasty trick to pull on someone!!! I live 4 miles from the United Chemi-Con plant and about 30 miles from Barker Microfarad (where mesa has there caps made) and having worked as an electrician in the plant can tell you that electrolyte is very dangerous stuff. It is highly carcinogenic and can cause severe allergic reactions in some people just by contact with the skin. The workers wear body suits during critical phases of the soaking process and many many of them have died from cancer. Get the picture? Never ever breath the dust from those old dried up caps either: back when those were made the electrolyte contained hefty amounts of PCB's.

Solder contains LEAD. Buy silver solder and always wash your hands real good after working on electronic equipment. Lead causes serious nervous system damage and can even cause sterility in men. Yup that's right, no ****? You can get "silver solder" at Radio Snack even or ask specifically for it at your electronics supplier.

 

[Buddy]

Yeah, at the age of 22 I was a little impulsive .. But he never took the valve cores out of my mustang's tires again .
Plus , a firecracker ,a 9v battery and a strand of wire buried in the toolbox drawer had an even more dramatic effect ...

 

[kdove]

I would agree ... good parts ... better than most ... mine has lasted 29 years and never been in the shop.

I do think I'm having trouble (loses volume occasionally for no reason) that may be related to the filter caps. At first I retubed ...still happens.

You can see the pictures of caps above ... they do appear to have some small bulges on the 30v caps. My replacements arrive tomorrow ... they are going in.

 

[stokes]

Mesa uses Illinois caps for their 220uf's and Sprague for the 30uf's.There is nothing "magical" about them.They are better than your run of the mill jap caps,but many amp companies use the same.Yes,caps can last for 20 or more years,but I have seen them fail much sooner.Years ago a supplier in Manhattan who is long gone,showed me a tech bulletin from Sprague which recomended they not be used beyond a 10 year shelf life,and yes I am aware that shelf life and useage life are very different,but why take the chance?When caps fail it is true they will blow the fuse,but a catastrophic (explode) failure and the fuse blowing will happen simultaneously.Once they get old,they dont always exhibit any symptoms,they just explode.When they explode they can take other components with them,not to mention the almost imposible mess they can make,and if not properly cleaned the electro can become caustic,if they get leaky they cause your PT stress due to drawing excessive current,a slow death for a PT.When caps are installed they should be "formed"or brought up to voltage slowly,if it isnt done the caps life could be shortened,if you didnt install them your self,you dont know if it was even done.I have experienced every type of cap failure,from the simple "ghosting" to the exploded mess.I would not take the chance with old caps,they dont last forever.I have heard from many people that Mesa tells them "dont worry about them",from my experiences,this is bad advice,I am not saying you should stay up nights worrying,but why wait for a problem,anybody with moderate soldering skills and can find their way around an amp chassis without getting fried can do it,and as I have said in other posts,I have never changed caps that were around 10 years old and not noticed an improvement in the amps response,the losses are gradual and you dont always notice any deterioration until it is severe,but you will notice the improvement.When I do a cap change for someone who is skeptical I always give the guarantee that if the owner isnt happy with the improvement,I will put them back,no cost.I have yet to have to put any caps back.And it is just good insurance against problems later on.There are different opinions and experiences on this subject,so it is up to the amps owner as to what he does,but you cant go wrong taking steps to prevent problems,just like changing tubes before they blow and take other components with them.