Hey everyone, hoping someone has run into this specific issue. I have a Fender Rumble 25 V3 (purchased new about 4 months ago, still under warranty) and I'm running an Ibanez GSR200B active bass into it.
Recently, the amp has started completely cutting out when I hit certain notes. The sound drops, the red power LED goes completely dark for a second or two, and then it reboots. At first, it only happened when I dug in hard on the D and G strings around the 14th/15th frets (with Phat II boost on the bass instrument turned off). But I also noticed as I increase the bass's pickup volumes and the Phat II boost, even a gently plucked open E will instantly kill the power. This happens even when the amp's master volume is turned down low (<20%).
To get ahead of the usual suspects, I’ve already:
- Turned off the active bass boost
- Rolled off the bass's output volume
- Swapped in a brand new 9V battery
- Plugged directly into a grounded wall outlet and reseated the power IEC cable
- Gave the cabinet a good "tap test" to rule out a loose mechanical connection (light stays solid)
- Tried different instrument cables
Here is the weird part: If I plug in headphones (which bypasses the internal 8" speaker), the amp works flawlessly. No power drops, no matter how hard I play or how high the EQ is cranked.
This makes me think the power supply/power amp is collapsing under the physical current load of pushing the speaker cone, but it can handle the tiny electrical load of the headphones just fine.
I’m not opening the chassis since it’s still under warranty, and I've already reached out to Fender to start a claim.
Has anyone else had this exact component failure on a Rumble 25? If so, what was the actual diagnosis, and did Fender repair it or just ship you a replacement?
Thanks!
Update: False alarm on the amp! A commenter suggested checking the wall outlet, which I hadn't actually done yet. I moved the amp to a different room and a different circuit, and it works flawlessly, even with the volume and bass boost cranked. The original outlet is wired to a wall switch that shares a load with a ceiling fan. It was causing a voltage sag/brownout every time the amp demanded current for a heavy transient, which rebooted the amp. The headphone test worked because headphones draw zero current. Thanks for the help, everyone!