Prophylactic replacement of power supply caps?

[Boomzilla]

Assuming that one has an otherwise-functional, decade old power amplifier with no remaining factory warranty, how prudent is it to replace the power supply capacitors?

Also assuming that such a change is prudent, how advisable are the following alterations to the circuit?:

1. Upping the capacitor voltage rating to the next step up?

2. Upping the capacitor microfarad rating within the physical limits of the chassis?

3. Bypassing the "main" power supply caps with a small-value film capacitor of much higher voltage rating?

My guess is that number 1 is always a good option with no possible side effects on the circuit. Number two probably won't make much difference in a properly designed power supply, and could actually degrade performance. Number three is not likely needed with "modern" polarized-electrolytic caps that have much faster discharge time (lower ESR) than older caps.

Thoughts?

Thanks - Boom

[405x5]

Yep.... leave it alone unless there is noise with no source material or audiable problems during operation.

If inclined to ASK such a question, you will know if something's up.

Bill

[Boomzilla]

Thanks, Bill. I'll at least do a visual inspection. If any of the caps are bulged or leaking, then it'll be time to consider replacement. At this age for the amplifiers, an annual visual inspection (with vacuuming of ambient dust) is probably a good idea.

[405x5]

Absolutely!
Mine are 16 years old and lookin like they just went in.

[405x5]

I did just change out a capacitor,
But not in the "Victrola".....
A dual run for my AC leaking

Bill

[KeithL]

1)
A capacitor of higher voltage rating, which is therefore being operated further below its maximum rating, will probably last longer.
(But that is one of those "all else being equal"statements.)

2)
Right on #2.
Adding more capacitance could improve performance; also might not improve performance; and might cause other components to fail sooner due to higher inrush current.
(Bigger caps require more peak inrush current to charge, which puts more strain on the rectifiers, and on any inrush limiters that might be included in the circuit.)
And, yes, putting in bigger ones shouldn't matter if the power supply was well designed, and so has ENOUGH capacitance there to begin with.

3)
This is always a more interesting question.
First off, there's no specific need for the bypass caps to be rated for a much higher voltage than the main filter caps.
The point is to use capacitors of a type with a very good ESR at high frequencies to filter out things like switching noise from the supply rectifiers.
(They usually end up being higher voltage simply because film capacitors, which have the best electrical characteristics for this role, are more commonly available in higher voltages.)
In general, even the lowest ESR and highest frequency rated electrolytics aren't going to perform as well at very high frequencies as relatively low cost film capacitors.
As usual, however, in many applications what's already there provides perfectly adequate performance, so there's not much reason to improve it.

As a very general rule, unless you're a design engineer, and have access to the relevant schematics, you're usually better off NOT second guessing the original designers.
I can't think of very many generalizations you can make about "upgrades" that are reliably true all or most of the time (and even substituting a "better" part can do significant harm under some circumstances).

Aug 2, 2017 10:28:38 GMT -5 Boomzilla said:

Assuming that one has an otherwise-functional, decade old power amplifier with no remaining factory warranty, how prudent is it to replace the power supply capacitors?

Also assuming that such a change is prudent, how advisable are the following alterations to the circuit?:

1. Upping the capacitor voltage rating to the next step up?

2. Upping the capacitor microfarad rating within the physical limits of the chassis?

3. Bypassing the "main" power supply caps with a small-value film capacitor of much higher voltage rating?

My guess is that number 1 is always a good option with no possible side effects on the circuit. Number two probably won't make much difference in a properly designed power supply, and could actually degrade performance. Number three is not likely needed with "modern" polarized-electrolytic caps that have much faster discharge time (lower ESR) than older caps.

Thoughts?

Thanks - Boom

[DYohn]

I agree with what's been said above. 1) don't fix it if it ain't broke, and 2) if you do it anyway, listen to Keith's advice.