Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers

SUMMARY AND UPDATED (8/20/16): THERE ARE TWO FIXES OUTLINED IN THIS THREAD.  ONE IS TO REPLACE DEFECTIVE CAPACITORS, AND THE OTHER IS TO CLEAN UP AND REMOVE THE CONDUCTIVE "GOOP" THAT'S SLATHERED ALL OVER THE PRINTED CIRCUIT BOARDS.  BOTH ISSUES RESULT IN CRACKLING AUDIO, STATIC, POPS, LOSS OF BASS, AND FADING IN/OUT SOUND.  HOWEVER, IT SHOULD BE NOTED THAT SIMPLY REPLACING CAPACITORS MAY NOT BE ENOUGH TO REPAIR YOUR SPEAKERS TO GOOD, OPERATING CONDITION.
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Crackling and Static Sound - CLICK HERE - What does it Sound Like?
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I purchased a pair of KRK Rokit 6 powered studio monitors back in January of 2012 from Guitar Center. Because of the nature of the equipment, I purchased the 2-year, extended repair/replacement warranty.  It was only $50 for better peace of mind. But wouldn't you know it, 10 months after the extended warranty expired, one of the monitors starting failing!  Now isn't that typical?!?  Upon power-up, one of the drivers emitted quiet crackling and static.  It sounded like when a dirty pot is rotated or an audio plug is wiggled/twisted.  Sometimes, this static and crackling would subside and not return, as if the monitor had "warmed up."  However, it wasn't until the crackling and static didn't go away that I decided to take action.
 
I am very familiar with board-level components, troubleshooting, repair, circuit design, soldering, etc. It's what I went to college for and up until a few years ago, I made and shipped original, audio and computer mod devices all over the world. My real job, however, has nothing to do with circuits and repair!  Haha!  But enough about me, let's talk about fixing these speakers!  Considering that most audio repair shops (if you can even find one), or the manufacturer, would most likely charge an exorbitant amount of money for the repair/replacement, I decided to put together this little "how to" guide for the benefit of the community.
 
• Skill level: easy; anyone can do this repair
• Tools Required: Philips screwdriver, precision snips, soldering iron ≥40W, desoldering braid, 63/37 solder (the good stuff) or lead-free solder, and of course the components.
• Components Required for This Particular Repair: 3300µF, 50V electrolytic capacitors (I chose part ECA-1HHG332 made by Panasonic, labeled as "audio grade," low ESR capacitors); and 2.2kΩ, 1/2W carbon film resistors (direct replacement to existing resistors).
• Cost of Repair: $10.85 (w/o shipping); I got enough components to repair both speakers.  All components ordered from Digi-Key. (My stock of a bazillion parts did not have such large caps and 1/2 resistors.  I have some 1W resistors, but not 2.2k).
 
Steps:
1. Turn monitor on it's side as shown and remove the 8, Philips pan-head screws around the perimeter of the backplate.

 
2. Take a small flathead screwdriver and pry the backplate from the cabinet.  Drop it down to the table.

 
3. Check out the capacitors and the resistors for trouble.  I've included pictures of the particular trouble that plagued my speaker.  NOTE: KRK put this awful, crusty black goo all over everything on the amplifier board. Basically, it's glue to hold various components and connectors onto the board, preventing vibrations from disconnecting or breaking them.


 
4. Essentially, the capacitors are used for positive and negative rails (±30Vdc) for the amplifier circuitry, perhaps in an AB class design.  The bulging capacitor means that it has failed.  The dielectric either dried out and/or the rail voltage exceeded the rating of the capacitor, causing it to fail.  In my haste, I did not pre-measure the failed capacitor's voltage while powered on.  This would have been a good tidbit of information.  However, I surmise that the root cause of the failure is the capacitor, which caused a high leakage-current which in turn raised the rail voltage thereby causing overheating of the 2.2kΩ.  Whew!  Anyway, we gotta get these garbage components out of here!
 
5. Rotate the backplate counter-clockwise into the cabinet, being careful not to overstretch the wires.  You could disconnect some of the leads, but why bother.  The goal here to to access the solder side (back) of the amplifier board.

 
6. Using the soldering iron at the highest setting and the desoldering braid (with a little flux), remove the two, 3300µF capacitors and the failed resistor(s).  I chose to not replace the resistor that was OK.  No reason to do it.  The capacitors, however, are crappola and need to be removed regardless of how they look!

 
 7. Here are the nice, new components:

 
 8. Install and solder the new components to the circuit board.  Hopefully you noted the orientation of the capacitors before you removed them!  Either look my pictures and/or note the silk-screening on the component side of the PCB.  Here are the new components soldered to the board.

 
9.  Reassemble the speaker by reattaching the backplate.  Do not not overtighten the 8, pan-head screws as the speaker cabinet is made of MDF.  The material is soft and the screws can strip easily.
 
10.  Test the speaker to see if the trouble is gone.  In my case, this fixed the crackling static!  Suh-weet!
 
I know the Cakewalk Forum is a little light on this kind of stuff, but I hope this is helpful to anyone finding themselves in need of such repairs.  Thanks for reading!

Heh, had to replace capacitors in my 30yro Yamaha M-80 audio amplifier once - still have it. The old bugger can do 30W in class A mode, which is really more than plenty, or 160W class AB...

Thanks for the how-to! I'm completely ignorant when it comes to this stuff, so it's very helpful to see how it's done.

Great post. I have KRK's. The V series though. Haven't had any trouble with them at all. But good to know this can be done.

Good post Tony well present with good clear pictures and written instructions.

Keep us posted, I have a set of those monitors. If you have the same problem again I may take some preventive action on mine.

UPDATE: So these speakers are about a gnat's butt away from going in the trash!  What a waste of $400, 3-1/2 years ago.
 
The other day, I opened up the speaker cases to investigate the new trouble.  One speaker had intermittent woofer operation, and the other speaker had static/crackling in the mid-range driver.  After some investigation, the IC amplifiers that power the units are TDA2052 (mid-range driver), and the TDA7296.  Both are 60W amplifiers, and I have no idea why KRK decided to use both at the same time.
 

 
Upon inspection, the TDA2052 was outputting about 200mV DC to the mid-range driver.  Not good.  It should be zero.  When the DC was "on the line", the speaker crackled and popped.  However, as the unit remained on after about 5 minutes, the crackles and pops subsided.  It was noted at this point in time that the DC was near-zero.  This screamed amplifier IC failure, so I immediately sought replacements.
 
After receiving the new components, I unsoldered the amplifier and replaced the old with the new.  Upon power up, the speaker did not work as expected.  The mid-range driver did not work.  When powered up, I observed some very quiet sizzling on the board!  WTH?!?!?  This was nowhere near the amplifier IC's.  It turns out that the black "goop" near the higher-voltage (+/-20Vdc) capacitors was sizzling!  I could see tiny bubble emitting from goop!  So what's this "goop" I speak of?  Well, it's like a glue that the jerk manufacturers sloughed all over the board to hold components and wires in place.  It turns out that this stuff was conductive.  Not good at all.
 

 
I managed to remove some of the goop and eliminated the sizzling.
 
However, at this point in time, the new TDA2052 was outputting 11V to the mid-range driver.  Again, not good.  Near this amplifier was more goop, that spanned a jumper and a resistor.  I cleaned up the goop as best as I could, and I noted the 11V dropped to about 10V.  So I continued to clean up more goop, but the voltage did not reduce any further.
 
Thinking the replacement TDA2052 was shot, I swapped it out with another (as I bought two of each amplifier IC).  Upon power up, the output to the mid-range driver was 0V.  Yeah!
 
All good, until the replacement TDA2052 let out it's magic smoke!
 
So there you go.  The black goop coats the circuit board in many places, most likely conducting and corroding where it shouldn't.  Overall, these speakers were doomed to fail since the date of manufacture.
 
I may try to clean up and put the other amplifier (i.e. the first swap-out) back in, but I'm not getting my hopes up.
 
I'll continue to update the thread as things progress further.
 
 

TheMaartian
Hey, down there in the valley. Greetings from up the hill!

 
Greetings!  Brrr, it be cold up in dem hills!  It was 62 this morning with a nice breeze.  Since I was up early before the sunrise, I enjoyed the morning coffee out on the lounge chair gazing up at the stars.  I'm definitely liking the cooler weather but miss the heat in a way.  Yeah I know, I'm crazy!  Back in Indiana, it's 32 with a butt load of snow coming--no thanks!
 

TheMaartianSorry for your troubles. I go back to discrete component days (designed solar-powered SCADA systems). Gotta say that I don't miss it. Don't miss programming in assembler, either. 
 
This whole Series of Unfortunate Events reeks of poor design margin. And cheap capacitors. Or expensive capacitors with flawed subcomponent(s). I had an issue once where new production of a very reliable product started failing in the oil fields (not a good place for failures; I never blew ANYTHING up; those bastidges at BP who bought out Amoco can rot in hell). After MUCH investigation and finger-pointing, it turned out that the Level-2 supplier of the tantalum powder to the capacitor manufacturer changes sources and failed to inform their customer (my supplier) of the change.
 
Could be something foreign in the goop. Or picked up from moisture/humidity over time.
 
Sorry you've been slimed.

 
The Amoco vs. BP thing is/was a huge deal back where I was from.  One of the country's largest refineries (Whiting) was near where I lived.  Not sure if things changed much when BP took over, but Amoco was a the all-American pride of the oil industry I'm sure.  Corporate buy-outs/take-overs don't come easy when it's a bunch of ferreners!
 
GOOD NEWS ABOUT THE SPEAKERS: I may have rectified the situation with the smoked speaker.  After swapping out the torched TDA2052 with the original IC, it seems to be working again.  So maybe the original was okay, but the good was affecting it.  More tests to follow.
 
So that means for the other speaker, I intend to clean up the goop first before swapping out components.  We'll see how that goes.
 

TheMaartianEdit: Hey, when you lived in NW IN, did you ever get a chance to visit the Sweetwater store? One of these days, I want to pack up my dogs (including the one that gets car sick, and take a nostalgia trip on the Mother Road (the hospital I was born in had a Rte. 66 address!)) and go visit that store. With a couple of credit cards. And debit cards. And GAS!

 
I never did visit the store, though I wanted to.  In fact, I never visited Fort Wayne the entire time I lived in Indiana!  It was pretty far from where I lived, but I was out that way one day for work on my way to the booming metropolis of Waterloo IN, and I drove past the store.  It was BIG!  At first I thought it was one of those warehouse/truck depots until I saw the sign.  I should have stopped in, but I needed to remain on schedule.
 
As for Route 66 goes, that sounds like an interesting trip, but I think the fun Route 66 stuff is here in the Southwest/West.  There's more of that nostalgic feel to it.  Maybe it's the desert/mountains, maybe it's the nice weather, maybe it's the open roads, or maybe it's a little of everything.  That and dinosaur statues!

dvdxyan
hey man,
thanks for posting this, same thing happend to me today.
 
can you post a link to the  2.2kΩ, 1/2W carbon film resistors that you got from digi?
dont know which one to buy
thanks!!

These speakers suck.  As I mess around with them more and more, the build quality of the board and mounting hardware is kinda bad.
 
http://www.digikey.com/product-detail/en/CFR-50JB-52-2K2/2.2KH-ND/665

dvdxyan
i know,but what can we do.. we already wasted the money on this junk
thanks!

 
True.

Great presentation. You should send it to Gibson.
 
If you are going to replace resistors I'd recommend you go with metal film. They are extremely quiet and don't seem to be bothered by thermal drift. I've not opened mine yet because they still work. This looks like a major design flaw at KRK and they should be doing something about it.
 
Probably somebody in China found an alternate goop that was way cheaper and substituted it for the manufacturer spec. Everything from electronics to wood flooring is coming out of China containing things we wouldn't allow in North America. Too bad you can't pull things apart at the store before you buy them.

KRK's are guaranteed for 3 years per this:http://www.krksys.com/krk-product-warranty.html
Therefor, if you bought a 2 year exended warranty from GC, then you should have another year on your warranty.

Hi, Mr. « 2.43 AM »
 
At the very beginning of this post last year, you wrote : “I am very familiar with board-level components, troubleshooting, repair, circuit design, soldering, etc. (… ) My real job, however, has nothing to do with circuits and repair!”
 
My situation is not far from yours, the difference being that I probably forgot much of my knowledge about electronic circuitry. Anyway, let’s go to my point:
 
I currently have the same problem with one M-AUDIO BX5A amplified speakers : its tweeter crackles at medium-high volume & frequency. I diagnosed that it comes definitely from the circuitry of one of my speaker. I disassembled its monitor case, the wiring is neat and no apparent bad BGoD.
 
MY QUESTION:  you did not explain how you identified which capacitor, resistor or chip is defective. On my circuitry board, there are approximately 40 components (resistors, capacitors, chips), and all seem neat, none of them bulges. So, how should i proceed to identify the failing component(s) ?
 
I join other people to thank you for the time you spent to share your knowledge.
 
I hope you can answer my question
 
Nicolas
 
Windows 7, Cakewalk UA-25EX external sound card, two M-AUDIO BX5A speakers

Nicolas59
I currently have the same problem with one M-AUDIO BX5A amplified speakers : its tweeter crackles at medium-high volume & frequency. I diagnosed that it comes definitely from the circuitry of one of my speaker.

I can't hear the type of crackle you're talking about, so what leads you to believe that the circuitry is at fault and not the tweeter itself ?
 
If you're not sure, you could always swap it with the other tweeter to elliminate the possibility.