basic electrolytic capacitor replacement?

[brianhood]

I called API about my A2D preamp breaking down on me, and over the phone the tech support guy determined(via me unscrewing the top plate) that i have a bad/blown capacitor.

He said that its a pretty easy thing to replace(as it seemed to be when i checked out "how to" videos on youtube), but it requires me taking the board out and possibly screwing more stuff up.

What would you guys do in my situation? I've called around town for the past hour, and only found 1 person that might be able to repair it for $65/hr

is there like a "go to" place for these kinds of repairs? Is there any way to replace this without taking out the board?

 

[KHE]

hi brainhood,

if you have no experience with soldering and replacing components, then i think its a better idea to let someone do it who has experience with this.

if its only a broken capacitor (SMD or THT), the work should be done in 15minutes, inclusive unscewing the enclosure.

ask in your local radio/tv-store for replacing the blown cap.

btw, there are ways to desolder a THT-Capacitor without taking out the board. but this is very critical for the pcb, you may damage it!

sorry for my bad english

regards, khe

 

[fitzrangerhoodngarb]

Take it to the tech.

Ask about a minimum bench fee and what time increments they bill in.

Again, take it to the tech.

 

[Chryst Krispies]

I read "Basic electrolyte replacement.."

Was going to say, " Gatorade dude!"

Sorry it's not that :/

 

[brianhood]

A quick update: It turns out that i was out of warranty by just 5 days, but the API service dude(Rabovan) allowed me to ship it to them under warranty anyways. My only expense was the shipping out there.

 

[aortizjr]

A quick update: It turns out that i was out of warranty by just 5 days, but the API service dude(Rabovan) allowed me to ship it to them under warranty anyways. My only expense was the shipping out there.

Ahh that is super cool of them.

 

[DasReich]

Capacitors only have a shelf life of five years, dodgy caps and scratchy pots are the things to expect on any less than brand new amp, although they often last a decade or more. You can sometimes tell when they are stuffed by looking at them as they start bulging or leaking.

 

[KHE]

Capacitors only have a shelf life of five years,

no. the lifetime of a electrolytic capacitor depends on the brand, quality and temperatur. if a long-life-cap has 8000hrs at 125°C, it will have 40`000hrs at 85°C.

 

[egan.]

no. the lifetime of a electrolytic capacitor depends on the brand, quality and temperatur. if a long-life-cap has 8000hrs at 125°C, it will have 40`000hrs at 85°C.

Yeah I was gonna say, I'm no expert but I sure do have a fair bit of 10-20 year old gear that's never been serviced by anyone besides deoxit.

 

[DasReich]

I stand corrected, thanks for clarifying that.

But I have seen quite a few amps with failing caps which aren't that old. Conversely I've had 70's marshalls still wearing their original power filter caps.

There is an interesting article on wikkipeadea about capacitor plague, where a lot of consumer grade caps manufactured in the late 90's have failed prematurely.

 

[Omega_Void]

Capacitors only have a shelf life of five years

no. the lifetime of a electrolytic capacitor depends on the brand, quality and temperatur. if a long-life-cap has 8000hrs at 125°C, it will have 40`000hrs at 85°C.

You're correct about lower temperature extending life in use.

But actually, DasReich is correct about the shelf life. When not in use electrolytic capacitors will gradually degrade as the oxide dielectric breaks down. This leads to excessive leakage current.

The capacitor then needs to be re-formed by putting a voltage across it for an extended period of time, which causes the aluminium surface to re-oxidise.

Electrolytics actually have a date code on them so you can tell how long they've been on the shelf, but different manufacturers use different codes and they change them from time to time, so it can be hard to find out what the code actually says.

Gear which has been unused for a decade will likely exhibit some problems as a result. The capacitors should gradually re-form during normal use, but electrolytics in the signal path may have difficulty as the signal voltage across them is too small.

According to repair guys, solder joints are the number one cause of problems, electrolytic capacitors are number two. In recent years they've been even worse as a lot of them were made using a bad formula causing premature failure. If you ever do have to replace, try for Nichicon or United Chemi-Con, or another Japanese-made brand like Panasonic, Elna, Rubycon, etc.

 

[KHE]

But I have seen quite a few amps with failing caps which aren't that old.

no wonder, there are a lot of guitar-amps which are horrible designed. Filter-Caps near the PowerTubess, cathode-cap mounted over the cathode-resistor in se-amps, not enough "headroom" from high-voltage to capacitor-rating-voltage...

regards, khe

 

[sirnak]

By reading the posts above, i feel like the conversation has gone a little off the topic. Anyways because of the off-topic-discussions, I am able to gain more information about the electrolytic capacitor's life. @Omega_Void: If I were to keep these caps in the shelf at 30 Celsius and if I were to keep apply voltage for a day or so and I continue this process every year. Do you think it would last for a long time like - 50 years? @brianhood: You must've gotten your board fixed from API long time ago. Since I just saw your post, I am wondering if you're still using the same amp. That info would be really helpful for me to make a decision on which one to buy from.

pcb assembly prototype