Capacitors at 50v vs 25v on replacement in preamp power supply?

[GoatGuy]

LOL back at ya, jean-paul. My handle is 25 years young, and I hope to see it to 30 years. Meanwhile, I battle the vapor-thin theories of snake-oil and magic charms. Brings out the best in people.

(PS: I use italics for posters' names, for titles of other articles, for bibliographic references, and for certain emphasis. jean-paul with the uncapitalized J seemd to need the italicization, by the first rule. Glad you like it... it takes extra time to type in.)

GoatGuy

 

[brucew268]

Jean-Paul thoughts on PSU?

- 10 to 100 µF 25 V standard electrolytic caps at the outputs of the regs and definitely not larger (if you like the regs to behave well that is). Check 78XX datasheets and you will read why. The regs don't fry or something like that but they will not perform any better and they possibly even oscillate at a low frequency with very large caps.

This was on the PSU of a preamp with 1000uF 63v spec'd both before and after the 7815/7915. I've heard that the cap after the regulator "forms a 'snubber' or 'zobel' that opposes the inductive impedance rise the regulator displays." If one uses a cap like Elna Silmic that does not have ultra-low ESR, the larger cap value is desired after the regulator.

Jean-Paul, I don't really understand these things but thought I'd ask your thoughts on that.

 

[Conrad Hoffman]

Arguments about when and what aside, one other thing to consider is the anticipation of failures. It's always good to consider what happens if a reg shorts out or a load goes open. The fewer parts that fry, the better. That's a possible reason to increase the voltage, though not likely the one the manufacturer considered. Lots of info about when and why and what on my site concerning caps- for some reason I've always been fascinated with 'em.

 

[brucew268]

Sorry to be unclear. By 'larger cap value' in the last post, I was speaking of capacitance rather than voltage.

 

[cbdb]

Using higher voltage caps greatly increases the caps lifespan.

 

[ticktock]

Using long life caps even more does.