KRK Rokit 6 speakers with no output.

[Mark1406]

I have friends who have given me a KRK Rokit 6 monitor to repair.

The problem is no output, the fuse was fine, the speakers are fine measuring 4 ohms, the caps aren’t bulging and I removed one and it measured fine.

I have noticed the corrosive, conductive (measures 25M on my Fluke 77) goop on the board and it’s destroying components. Currently, I’m removing most of it. The problem with that is it’s hard to identify component values as alcohol doesn’t remove the goop. Once I have that done, can start fault finding in ernest.

I suspect the issue might be a problem with the mute line, but I haven’t powered up the amp with the case open yet.

Thanks for looking at my post and I will post more details going forward.

Regards

Mark

[Audiorepair]

Yes the mute circuit usually gets eaten by the corrosive glue.

I have a list of the usual suspects stored, from repairing other units.
There are now schematics available, some resistor values may have been changed over the years, so try and read what you have/had if possible.
 
Replace also the two diodes DL100/101 (1N4148) as if you move one you will usually find its been eaten too.

Rokit 6 R100 2K2 between main caps
R105 4k7  RH100 10k  RH101 11k
RL106 30K RH105 10K R108 2K
RH104 11K


I always remove the speaker flying leads and cut off the destroyed ends and refit them, you'd be daft not to.

[Mark1406]

Thanks so much for your informative reply. You were dead on the money the 4.7K resistor (labeled 10K in the diagram) was missing one leg. I still have more black goop to get rid of, but I feel quite positive that this is the fault.

Really appreciated your help.

Regards

Mark

[Audiorepair]

Looking back at my Database, the first time I repaired this KRK corrosive conductive black goo issue was in October 2010.

So it looks like KRK may have made a decision not to actually do anything about it?
Go figure.

[Mark1406]

Thanks for your help. I ran into another issue the mica washer on the HF output device was a mess and fell apart when I removed the heatsink. I didn’t notice this and the IC was making contact with the heat sink which blew the fuse and has taken out the 1N5392 rectifier diodes. I think it should be good after replacing the diodes and fuse. I have never seen a mica washer fall apart with such ease, it’s most unusual.

I will post progress on the repair for others who come across this fault.

[Mark1406]

The monitor worked like a charm, though the other monitor had low output and stopped working. So I now have the other monitor to repair.

I removed goop and replaced the 10K, 30K and two 1N4818 diodes. The 2.2K resistor across the 3300uF filter cap was shot.

The fuse is fine, I suspect the mute line again.

Regards

Mark