I wasn’t expecting to make this video, but my computer editing monitor speakers just failed. Obviously that puts a spanner in the works regarding content creation.

I completely strip down a non-working Presonus Eris 3.5 Generation 1 studio monitor and replace its failing electrolytic capacitors to repair a problem where the monitor speakers were not working. The Eris 1 was not powering on and seemed dead. The stock caps were cheap, low-quality parts that had become faulty from heat. As one audiorepair forum user noted, the original “cap-top” capacitors in these monitors are “absolute sh**e” and prone to failure.

Inspection & Teardown: Opened the active Eris 3.5 monitor and examined the circuit board. Bulging or corroded electrolytic capacitors were identified as the likely culprits.

Capacitor Replacement: All faulty low-grade capacitors are desoldered and replaced with premium new ones (same capacitance/voltage, premium brands). Each component is matched for size and orientation to ensure a proper fit and performance but I do make a small mistake as you’ll see in the video.

Testing & Verification: Each removed capacitor is tested with an ESR meter – most old caps show high ESR or shorted electrolytes, confirming failure. After installing the new caps, I power up the speaker and test it; the power issues are resolved and the monitor works like new.

Incidentally, other Presonus users have observed similar problems. A PreSonus forum report describes one monitor only working when its 100µF power cap was heated with a hairdryer – cooling would cause white noise and shutdown. That’s exactly the kind of intermittent failure heat causes in cheap electrolytics. By replacing all the weak capacitors with high-quality parts, we avoid this trap. The end result: a fully repaired Eris 3.5 monitor!

Presonus Eris 3.5 Replacement Capacitor List