My Mackie 1400i thumps when I turn it on - Mackie Music

Contact Mackie direct. They will know which component is failing. Link to the company for one of their powered speakers.

Thump215 15" 1400W Powered Loudspeaker

Mackie https://mackie.com > loudspeakers > thump-series-2022

The Mackie Thump215 15" 1400W Powered Loudspeaker brings the bass for DJs, venues, bands, and more and features a feedback eliminator and music ducking.

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Question edited for clarity

https://elektrotanya.com/mackie_thump_th-15a_sch.pdf/download.html

Or contact Mackie direct
https://mackie.com/sites/default/files/PRODUCT%20RESOURCES/MANUALS/Owners_Manuals/Thump12A_Thump15A_OM.pdf

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See my previous answer. Service Locator Mackie

Is this a new problem? In other words, was it working correctly at some point?
You ned to isolate the problem. Plug a different source into the speakers and plug the mixer into a different amp/speaker. See which part isn't working correctly.. Either way, it's likely you need to take the part that's not working to the shop. You can contact Mackie to find the nearest service center. Service Locator Mackie

Contact Mackie Customer Service for the best answer. Mackie Tech Support

Your best bet is to contact Mackie Tech Support. Here is a link to their Suppot page. Mackie Tech Support
it's likely it needs to go to a repair shop. Here is a link to their service center finder. Mackie Service Center Locater

Yes, it's normal. You can probably turn the speaker volume down to minimum before turning them on to minimize it.

"How to replace bass driver in mackie thump 15a".
Did you mean,disassembly the speaker enclosure?
Just remove the 16 screws at the rear cabinet, using a screwdriver.
Then remove the 4 screws that secure the speaker, using the hex key. Is the bass driver blown up / broke?

Jose Miguel Carcamo Cruces do you have pictures of these j112 fet ? Thank you!

replace diodes D106 and D107