What would you do?

[Oldmactech]

I have a Line 6 AXS212 modeling amp. Supposedly the worlds first modeling amp. Complicated as heck but really has some decent sounds. Built in 1994 if I recall.

Ran onboard diagnostics and the 3 volt battery is dead. ( amp is 25 yrs old so not surprised.) I assume the battery is for creating custom presets.

Took the cover off and thing is pristine under the hood except for the dead hard wired battery. I ordered a battery, (some places wanted $35 for one) and will replace it soon.

I really don’t want to disturb the logic board PCB but I’m wondering if it would be a good idea to pull, test and possibly replace the power section main capacitors while inside. This amp has seen very little use for several years. I suppose I could remove from the circuit to test but rather not disturb perfectly good solder.

I should say that one of the switching channels sometimes exhibits a noise but that may just be operator failure.

Just curious.

thanks.

[glebert]

I say don't go looking for problems.

[Tom Phillips]

I say don't go looking for problems.

I agree. No swelling tops are evident on the caps so I would replace the battery first and evaluate the overall operation before replacing parts.

[Oldmactech]

Wise council.

interesting how this tirelessly complicated amp is seemingly so sparsely assembled.

question: do caps degrade from time or use or combo of both?

[Helmholtz]

Bad filter caps typically show by ripple/hum.

[Helmholtz]

question: do caps degrade from time or use or combo of both?

Both, but effects are different.

1) Long time storage without charge increases electrical leakage (leakage current). This effect is may be reversible.
2) Long time use dries up the cap, thus lowering capacitance and increasing ESR. Effect is non-reversible.

Both effects are accelerated by elevated temperatures.

[Mick Bailey]

I would leave them alone - caps in SS amps usually have a long life. If there's no hum, just visually inspect the caps for lifting off the PCB (terminal end bulging), the can top bulging (but don't confuse this with the insulating disk bulging, which is common - press it down and see if the can is flat), and check for oozing or leaks between the cap and PCB. Other than that I do an in-circuit ESR test - no need to remove the caps for this but make sure they're discharged if your meter is one that can't measure a charged cap.

[teemuk]

That's not even an old amp. I have stuff from early 1980's and late 1970's filled with electrolytic capacitors and they work just fine. This "aging" thing's been blown out of proportions; those caps last much longer than people think and if the ancient parts in vintage amps fail there is no correlation with modern parts.

I concur: Don't fix what isn't broken.

[J M Fahey]

Wise council.

interesting how this tirelessly complicated amp is seemingly so sparsely assembled.

question: do caps degrade from time or use or combo of both?

*Lack* of use is bad for electrolytics, having voltage applied keeps ions where they belong.

[Leo_Gnardo]

question: do caps degrade from time or use or combo of both?

When I was a young pup, say 24 ish, a senior technician was sent from Varian to tune up our new ion implanter. During a break, this "senior" - grey haired, haggard looking, seriously experienced - explained electrolytic caps to me this way. "If they were left fully charged all the time, they could last more or less forever. Uncharged is when they break down." And over subsequent decades it seems the ol' geezer was right, and now I get to be the old geezer passing it along.

Through decades of experience I have found two things matter, quality of manufacture AND exposure to heat and overvoltage. Some electrolytic caps never stressed to their limits seem to last 50+ years (70's Ampeg V2, V4 & similar), but caps that were crappy to start with (50-60's Gibson/Epiphone) gave up decades ago and whenever seen in the modern amp repair venue, really should be replaced without another thought.

[Helmholtz]

The insulating properties of an ecap depend on a very thin layer of aluminum oxide (the actual dielectric) on the anode foil.
This is produced by electrolytic oxidation with applying a "forming" voltage of around 1.5 times the rated voltage during production.

When an ecap is not charged a reverse reaction starts which slowly eats/etches tiny voids into the oxide layer causing electrical leakage.

A charged cap constantly re-forms and heals itself.