Replacing tantalum caps in an Orban 674A

[pvision]

I am recapping an Orban 674A. Many of the small electrolytics have started weeping slightly. There are four tantalum caps in the output stage that I'd like to replace but am not sure with what

They are 22 uF, 15 Volt tantalum caps. Can I replace then with electrolytics or should I use something else? A little bit of research suggests tants might have been used here for decoupling due to their low ESR. The output circuitry is above my pay grade and I'd rather not make assumptions

Suggestions?

 

[JohnRoberts]

I am recapping an Orban 674A. Many of the small electrolytics have started weeping slightly. There are four tantalum caps in the output stage that I'd like to replace but am not sure with what

They are 22 uF, 15 Volt tantalum caps. Can I replace then with electrolytics or should I use something else? A little bit of research suggests tants might have been used here for decoupling due to their low ESR. The output circuitry is above my pay grade and I'd rather not make assumptions

Suggestions?

Those caps are bootstrapping drive circuitry.

ESR is not significant. Modern Aluminum electrolytic caps should be fine IMO. 

JR

 

[pvision]

Thanks, John

 

[TheJames]

Is there any particular reason for replacing the Tantulums?  Are they known to degrade over time?  I've always known to fail to short (catastrophically) but never to necessarily deteriorate like electrolytics do.

 

[JohnRoberts]

Is there any particular reason for replacing the Tantulums?  Are they known to degrade over time?  I've always known to fail to short (catastrophically) but never to necessarily deteriorate like electrolytics do.

There are different types of tantalum caps but they all degrade eventually. Field crystallization is a common failure mode.

The caps in that circuit position do not appear very stressed (ripple current can trigger tantalum cap failures).

Of course if the cap ain't broke don't fix it. Unclear why tantalum was used in the original design other than tantalums were small for the amount of capacitance back in the day.

I do not like leaving old tantalums where they can cause mischief. Modern ones are more reliable, while aluminum should be fine and cheaper.

JR 

 

[pvision]

Many of the small electrolytics in this Orban have green, furry legs from leaking electrolyte so I decided to replace all the electros. It would seem remiss to leave the tants untouched due to their reputation for failing short-circuit

The only other time I've been exposed to tants - in an Ampex ATR100 - they were failing

Nick Froome

 

[fazer]

Others have suggested to replace tants as well as electrolytic for failure on bypass caps that create damage to circuit cards.  I just replace caps in a Red 6 focusrite and I loved the openness of the sound.