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

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2:43AM
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2014/11/16 11:54:19 (permalink)

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!

post edited by 2:43AM - 2016/08/25 12:01:50

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#1
Shambler
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/16 14:02:09 (permalink)
Nice one! Capacitors are always the first port of call especially in much older equipment than your krk's.

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/16 16:58:25 (permalink)
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...

laudem Deo
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/16 17:34:39 (permalink)
Excellent post on repairing your speaker.  Can apply to others, as long as there is physical evidence. 
 
I used to do amp-repair (in Nashville) and wouldn't attempt anything I didn't have a schematic for.  Sometimes you get lucky and find the parts, such as your repair, but for a repair shop you can't take the chance.
 
But, your detailed explanation gets a "gold star".

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#4
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/16 19:37:30 (permalink)
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.
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/16 22:16:10 (permalink)
Yes excellent post! Funny those parts went south? I guess s--t Happens

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/17 01:34:14 (permalink)
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.

Grem

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/20 14:56:38 (permalink)
That was a nicely presented project with good information and illustrations. Well done!

Regards, John 
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2014/11/23 13:27:55 (permalink)
Good post Tony well present with good clear pictures and written instructions.

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/08/15 00:11:53 (permalink)
Wow.  These monitors are pure garbage.  The crackling is back, now worse than ever...and in both speakers.  I have recently moved, and I don't think they survived the trek across country despite being packed in their original boxes and Styrofoam inserts.
 
Back to the workbench!
post edited by 2:43AM - 2015/08/15 00:19:45

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/08/15 03:09:26 (permalink)
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.

Regards, John 
 I want to make it clear that I am an Eedjit. I have no direct, or indirect, knowledge of business, the music industry, forum threads or the meaning of life. I know about amps.
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/08/15 06:57:15 (permalink)
That's ridiculous! I'm sorry for your troubles. Please let us know what the problem was, and post more pictures!
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 00:42:06 (permalink)
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.
 
 
post edited by 2:43AM - 2015/11/21 00:56:12

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#13
TheMaartian
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 07:38:41 (permalink)
Hey, down there in the valley. Greetings from up the hill!
 
Sorry 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.
 
I'm happy the only sound coming out of my BX8 D2's is very low level 60 Hz hum. So are my dogs. They're still sleeping. 
 
Edit: 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!
post edited by TheMaartian - 2015/11/21 07:58:29

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#14
2:43AM
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 10:01:15 (permalink)
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!

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 10:09:37 (permalink)
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!!
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 11:08:09 (permalink)
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
post edited by 2:43AM - 2015/11/21 11:19:13

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dvdxyan
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 11:10:22 (permalink)
i know,but what can we do.. we already wasted the money on this junk
thanks!
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 11:21:06 (permalink)
dvdxyan
i know,but what can we do.. we already wasted the money on this junk
thanks!

 
True.

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 12:34:51 (permalink) ☄ Helpfulby Antilles03 2017/11/10 16:18:07
Well, it's all in the goop!  Thank you KRK manufacturing team for the Black Goop of Death!
 
Speaker #2 repaired without replacing any components...well, at least not the amplifiers!
 
Check it out.  I encourage all those who are repairing their Rokits to clean out the goop between components.  Seriously, this stuff makes a complete mess.  It hard and you must either chisel it out or find another means.  Rubbing alcohol doesn't seem to penetrate the stuff, but it does clean up the area after it has been removed.  Acetone may prove to be more effective.
 
Location of previous repair last year, the replacement of the 2.2k ohm resistor, which was cooked.  But note the corrosion of the jumpers.  I replaced the capacitors (removed) in this area as well, as they both were bulged and had failed.  The goop got 'em!

 
All cleaned up and much better!

 
Another area that was cleaned up.  This area also sees raised voltage levels (+/-20V) and the jumper and the components showed signs of corrosion.  I also replaced these capacitors as well (not shown).

 
After cleaning up all the areas shown above, the speaker turned on and sounded good!
 
So my advice?
 
1.  Check the boards for corrosion and areas where the Black Goop of Death covers multiple components, especially jumpers.
 
2.  Remove the BGoD using chemicals, a pick or X-Acto blade.  In my case, I used a hot soldering iron with a chisel tip + X-Acto + isopropyl alcohol.  If you use your soldering iron, then be sure to clean it well afterwards.
 
3.  Replace burnt resistors and bulged capacitors.  Overall, I think it's a good idea to replace all of the power capacitors.  The two in the middle are 1000uF 35V electrolytic caps.  I replaced them with 50V versions.
post edited by 2:43AM - 2015/11/21 12:47:43

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ampfixer
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/21 20:20:38 (permalink)
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.

Regards, John 
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/24 08:41:15 (permalink) ☄ Helpfulby Antilles03 2017/11/10 16:18:34
UPDATE: It's been a couple of days and I am happy to report that the speakers are still working well!

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/27 17:48:46 (permalink)
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.

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/28 03:02:16 (permalink)
When I look at the pictures now, it looks like that goop was ejected by capacitors boiling over. Another funny thing is the lack of visible solder on the component legs. If you soldered boards properly some solder would wick up the component legs and be visible topside. The boards are being wave soldered after being stuffed with components. 
 
The repairs you are making are better than the original build quality.

Regards, John 
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/29 10:51:29 (permalink) ☄ Helpfulby Antilles03 2017/11/10 16:18:56
Lynn
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.

 
Oh well.  I fixed the speakers and they're holding up well.  And I got it done in a couple of days rather than a couple of weeks plus the expense of shipping.

ampfixer
When I look at the pictures now, it looks like that goop was ejected by capacitors boiling over. Another funny thing is the lack of visible solder on the component legs. If you soldered boards properly some solder would wick up the component legs and be visible topside. The boards are being wave soldered after being stuffed with components.

 
It's not capacitor dielectric unfortunately.  That would have been better, and it probably wouldn't have conducted in the manner in which it did.  It would have just been messy.  I remember I fixed an old copy machine many years ago, and the goop slopped out by a BIG failed capacitor was a weird silicone-Teflon mix.  Syrupy but extremely slick when wiped clean and dried!  Depends on the capacitors though.  Not all are "wet" inside.
 
The goop is stuff to hold components and wires in place...like a hard tar.  I've seen this used on other boards, but it's mostly a white caulk or straight silicone.  Either one is better than this garbage.  This stuff probably dries fast, so it was used on the PCB assembly line for that rapid-fire production.
 
ampfixerThe repairs you are making are better than the original build quality.

 
I agree!  Thanks for the support!
post edited by 2:43AM - 2015/11/29 11:04:42

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Paul P
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/11/29 12:43:47 (permalink)
 
Well, this was a fascinating story which I only just now read in its entirety.  Glad things worked out in the end.  You've given us several things to keep in mind as we go forward.
 
Thanks for taking the time 2:43AM  (and be sure to let us know if anything changes )
 

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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/12/02 12:34:48 (permalink)
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
 
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/12/02 14:10:49 (permalink) ☄ Helpfulby Antilles03 2017/11/10 16:19:02
Nicolas59 
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)?



First and foremost...THANKS!  For my failed components, they were visually identified as highly likely to have failed.
 
 
When troubleshooting any faulty electronic circuit/device, start from what can be observed: sights, sounds, smell, touch.  Are there any burnt or discolored components?  Are there sounds that lead you to a particular section of the PCB or component?  Does the problem start and go away after awhile?  Does anything smell "hot" or burnt?  Do any components feel warm or hot?  CAUTION: always be aware of high-voltages which could shock you, i.e. be especially careful around "mains" voltages, amplifier rails, switching power supplies, and high-voltage capacitors.  Obviously, you don't want to be touching these while energized, and some capacitive circuit retain a charge.
 
This is the stage in which I found the bulged capacitors, which were identified to be a highly likely source of circuit failure...electrically.  I say this because at this point, you would have determined the capacitor to be physically failed, but electrically it may still hold up and allow the circuit to operate within its design parameters.  So without further testing of the capacitor, such as ESR and capacitance tests, you would never know the complete "truth."  So the next logical step is to replace what appears to be failed and retest.
 
Following up to visual checks on the components, and certainly something to check before ordering components, is to visually check the printed circuit board itself, all solder traces, and all soldered connections.  Hairline fractures, cold solder joints, and bridged pads can all lead to problems.  To check for loose connections due to loose components, try lightly pressing on components or parts of the PCB while the circuit is turned on, again being careful around hazardous voltages.  You may hear the problem stop or get worse.  As a follow up, use a magnifying glass to inspect around the PCB.  I use a 10x loupe.
 
In your particular case, you have observed the static coming from the tweeter.  So trace the wires from the tweet back to the PCB.  In most cases, and good board design, the various circuits (and its components) are grouped together.  So chances are, the fault component will be relatively nearby the wires going to the tweeter.  I wouldn't rule out an amplifier failure, but hopefully you can replace some basic components for the fix.
 
Another troubleshooting practice is to check voltages with a meter and/or oscilloscope.  But unless you have a schematic and/or component datasheets available (as well as the tools), are versed in electronics, then I would refrain from doing this.  It's not for the faint of heart!  When a device is powered up, one can easily hurt the components, the board, or themselves!
 
I'm proud to say that I successfully brought an Alesis A6 Andromeda back from the dead by repairing it myself, a feat that's was both daunting (since I took the risk of buying a dead one) but also highly-rewarding.  You may read about it here if you wish https://www.gearslutz.com/board/electronic-music-instruments-electronic-music-production/985035-troubleshooting-alesis-a6-andromeda-no-boot.html), and the thread spurred other great troubleshooting by other people, reviving a few more dead Andromeda's:
 
Feel free to PM me any questions, and I will certainly help you out with the repairs!

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#28
Paul P
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/12/02 21:43:32 (permalink)
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.
 
 
post edited by Paul P - 2015/12/02 21:55:52

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Nicolas59
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Re: Shade Tree Repair Guide: Crackling/Static in KRK Rokit 6 Speakers 2015/12/10 13:40:56 (permalink)
My answers to both Paul and 2:43AM,
(please apologize for my silence for the last week, I was quite busy)
 
to Paul: yes precisely that is what I did, swapping the tweeter.. and the noise "did not swap". I also swapped left and right channels from my Cakewalk sound card. Same? That is how I came to my conclusion.
 
to 2:46AM: thanks for your comprehensive answer. My next steps will be to do these two tests that you suggested : (i) checking component temperature when in use, (ii) gently pressing on components when playing to see if it impacts the noise.
 
NOW AN UPDATE : I have not done yet these steps, but a new situation has arisen. First, let's name my monitors: Monitor A is the faulty, Monitor B is the good one. Since I swaped the tweeters last week, I have been listening to some music on my monitor B alone, now equipped with the tweeter from Monitor A. And this was OK.... well it WAS because it IS not anymore: for the last 2 days, I have some new annoying popping or crackling noises now in Monitor B.
 
Shall I conclude that the original A tweeter is responsible for "contaminating" the electronic circuits that feed it !?! It looks as if there is a sort of interaction between one and the other... it looks as if my tweeter is a Killer ! killing the electronic, would it be possible ?
 
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