Krk Rokit 8 g2 loud buzz humm repair

[lostbandicoot]

one day when i switched on my KRK Rokit 8 G2 Active studio monitor, i get a very loud humm/Buzz very much like in this video here :

[

i had assumed it would probably have something to do with damaged or old Capacitors & or a known issue where the manufacturer uses a type of adhesive AKA Black goo of death that becomes conductive overtime. so what i first did was remove as much black goop as i possibly could and cleaned it with isopropyl alcohol.

next step was replacing some of the larger caps and resistors

C100 & C101 - 2x 4700uF 50V

C108 & C109 - 2x 1000uF 35V

R100 & R101 - 2x 2.2K 0.5W

CL100 & CL103 - 220uF 16V (Because i had them lying around from a previous project)

after these replacements i then connected everything back together, switched on the speaker and the Humm was still there.

 

[micolas]

one day when i switched on my KRK Rokit 8 G2 Active studio monitor, i get a very loud humm/Buzz very much like in this video here :

[

i had assumed it would probably have something to do with damaged or old Capacitors & or a known issue where the manufacturer uses a type of adhesive AKA Black goo of death that becomes conductive overtime. so what i first did was remove as much black goop as i possibly could and cleaned it with isopropyl alcohol.

next step was replacing some of the larger caps and resistors

C100 & C101 - 2x 4700uF 50V

C108 & C109 - 2x 1000uF 35V

R100 & R101 - 2x 2.2K 0.5W

CL100 & CL103 - 220uF 16V (Because i had them lying around from a previous project)

after these replacements i then connected everything back together, switched on the speaker and the Humm was still there.

View attachment 142918View attachment 142919

Does the defective monitor have a brother?

 

[lostbandicoot]

Does the defective monitor have a brother?

Haha yes, the defective monitor does have a brother, and is working fine.

 

[micolas]

Haha yes, the defective monitor does have a brother, and is working fine.

Then everything will be solved!
Happy New Year!

 

[lostbandicoot]

Does the defective monitor have a brother?

Haha yes the defective monitor does have a brother, and is working fine.

Then everything will be solved!
Happy New Year!

Err, happy new years? But doesn't really help the problem I have

 

[Khron]

But doesn't really help the problem I have

Might be worth checking all eight diodes in the rectifier bridges in the power supply.

If you apply audio to the input, do you get any sound from the drivers, in addition to the noise?

 

[micolas]

Haha yes the defective monitor does have a brother, and is working fine.

Err, happy new years? But doesn't really help the problem I have

Okkk!
You have two identical monitors, one of which works perfectly.
Most probably the electronic modules are mostly interconnected with multiple connectors.
So with a lot of old Chinese patience (it's an expression from my country) you will connect the functional power supply in the monitor with humm. If it works normally, you will know that it is a defect in the power supply.
If not, then it's about the audio part...
But then, first of all, you will have to check the xlr, jack, rca, etc., switches, potentiometers, etc. located on the back panel of the monitor. And the screws, cables, fixing contacts to the table, between metal parts, etc. Even the cables with which you connect the monitors to the audio interface.
If everything is ok, only then do we approach the audio pcb(s) (preamps, crossover, poweramp, etc.)
Sound like a working plan?
Good luck!

 

[Khron]

you will connect the functional power supply in the monitor with humm. If it works normally, you will know that it is a defect in the power supply.

... Except that the only separation is at the transformer, ie. the rectifiers & smoothing caps are "already" on the amplifier board; "best" thing one can do is connect the transformer from the "good" monitor to the supply/amplifier board of the "bad" one

 

[micolas]

@lostbandicoot
And one more thing: listen to @Khron's advices, he is a very experienced and generous man (but don't upset him!)