replace electrolytics on old pedal?

[arfy]

I just replaced the jacks and rewired to true bypass an old Ibanez PT909 that sounds nice but was a little bit of a tone drain before.  I'm wondering if I should replace the electrolytics like you would in an amp of a comparable age.  The only one I'm sure is a power related cap is a 33uf, there are several 4.7 uf's that I think couple the audio stages.
Is there any advantage/reason to getting some nice new Panasonic caps from Digikey and replacing these?  It's pretty tight on the board so upgrading in terms of voltage probably wouldn't fit, there is no 9 volt adaptor but I'm using it with one of those cords with a 9v clip on one end and a plug to the 9v power supply on the other end.
Really nice sounding pedal, by the way.

[niftydog]

if it sounds good then I wouldn't screw with it.

If I were in your shoes, I'd be using my fancy-shmancy in-circuit cap tester just to be sure, but I wouldn't expect to find anything wrong.

[aron]

Yeah, if it sounds ok, leave it.

[Mark Hammer]

A reasonable concern, but the question of age and obligatory replacement is one of relative age, based on technology of the time.

Should one "replace" a computer that was made 10 years ago?  Probably, since a more recent one will likely be able to accomplish more.  Should one replace a 1990 typewriter?  Not necessarily.  Do 10 year-old tires need replacing?  Probably.  Does a 20 year-old toaster that works fine need replacing?  Not necessarily.

Caps from 1962 may well need replacing, or at least verification.  Caps from 1980 are likely of a vintage where the technology employed is less likely to result in declines over time.  We're not talking about those big D-cell sized power supply caps that dry up, here.  We're talking about reasonably small electrolytics that are still up to spec, and certainly not exposed to the sorts of temperatures that might corrupt their functioning as one might encounter in a tube amp that regularly keeps ALL components, not just the tubes, warm.

What likely HAS changed in the intervening years, are the op-amps available to mere mortals like you and I.  Consider unsoldering one of the op-amps on the board, installing a socket, and trying out some of the devices that have made themselves available to us over the years.  There ARE things better than a 4558.  Just be careful not to damage the original chips by overheating.  Solderwick with a wee bit of liquid flux on it does a nice job of extracting solder with minimal difficulty.

[RedHouse]

Yes I'd like to emphasise Marks statement about temperature, it's definately the temperature and high voltage in tube amps that make them be automatic replacements, the goo in the electrolytics dries out.

[TheBigMan]

I've only ever replaced the electrolytics in one pedal.  That was an Ibanez SD-9 which had a leaky power supply filter cap.  Leaky to the extent that the board traces were slightly corroded.  I decided as a precaution to replace all the electrolytics seeing as I had all of them in stock anyway.

[R.G.]

I have an heretical opinion.

If
(a) you have a pedal more than 10 years old
(b) you use it on stage, not just in your bedroom where it doesn't matter
and
(c) you even think of whether to replace any parts
then replace all the electrolytics.

Yes, you will inevitably replace some that were still good.

But ask yourself - how long until any one of these fails? They are all at or near the end of their designed life. It only takes one of them failing to make the pedal not function. Will that happen today, tomorrow or in five years? No one knows. But it *will* happen.

Parts reliability is a classical bathtub curve. Failures are high when the parts are first used as "weak" ones fail. Then there is a long maturity phase where the normal parts give good performance, and finally a higher failure rate as wear-out starts. If you've already had the maturity, you're staring wear-out in the face.

Of course, if it only plays in your bedroom, it doesn't matter.  You can fix it whenever it breaks - you don't have to rely on it.