Loud low frequency humming from KRK Rokit 8 G2

[EX_killer]

Hello,

Looking for advice on how to possibly fix loud humming from my KRK Rokit 8 G2. It emits a low frequency hum when the speaker gets warmed up, ~15 mins of on time. It hums on any type of input and even without any inputs. Thought it was a ground loop error, rented a power conditioner to no avail. Took off the back and inspected the circuits no bad caps or any of the sort, even replaced the largest power filtering capacitors. The 4700uF and 1000uF ones still to no avail. Any possible solutions to this? I have access to good soldering/de-soldering equipment and about to buy new speakers so having these as backups are nice.

Also it only started happening to one speaker randomly. Not sure if its a bad speaker or transistors/chips started to give, I'm willing to tear this apart as a learning experience so anything helps!

 

[ecc83]

Hello,

Looking for advice on how to possibly fix loud humming from my KRK Rokit 8 G2. It emits a low frequency hum when the speaker gets warmed up, ~15 mins of on time. It hums on any type of input and even without any inputs. Thought it was a ground loop error, rented a power conditioner to no avail. Took off the back and inspected the circuits no bad caps or any of the sort, even replaced the largest power filtering capacitors. The 4700uF and 1000uF ones still to no avail. Any possible solutions to this? I have access to good soldering/de-soldering equipment and about to buy new speakers so having these as backups are nice.

Also it only started happening to one speaker randomly. Not sure if its a bad speaker or transistors/chips started to give, I'm willing to tear this apart as a learning experience so anything helps!

Was the heatsink carrying the output devices (might be a big chip) hot? If so that indicates thermal runaway and the amp will ultimately destroy itself and maybe take a speaker with it.

You will need to have the guts out on a table and pounce with a can of freezer to isolate the problem. Could be a bad joint and so judicious tapping with the handle of a screwdriver could locate the fault.
If no joy when the giblets are exposed (better cooling) you could warm things up gently with a hair dryer...NOT a bloody paint stripping heat gun!

Now, you come across as an intelligent chap with some experience of electronic gear but PLEASE, be very careful around the mains input circuit!

Dave.