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KRK VXT8 Blown Capacitor?
Old 19th September 2014
  #1
Gear Head
 

KRK VXT8 Blown Capacitor?

Hello all,

About a week ago my left studio monitor (krk vxt8) started making a horrible crackling and popping noise. I tested it in multiple power outlets with no audio cables of any kind plugged in and the noise persisted for the most part (other than what appeared to be random periods of quietness). Eventually the tweeter seemed to have blown as no sound was coming from it any longer.

Since my speakers are out of warranty, I opened them up to take a look. I first tested the tweeter from the other monitor which was working in the broken monitor to see if maybe that was it... good tweeter didnt work. After taking a closer look at the PCB board of the bad speaker it looks like one of the capacitors has given up its will to live (pictures attached).

My question is, can I replace this myself? and does all the black that appears to have leaked on to the other capacitors matter? Other pictures ive seen of blown capacitors are just sort of popped tops.

Any help on this matter would be greatly appreciated.
~keep it slutty~
Good speaker....
https://dl.dropboxusercontent.com/u/...2014.21.26.jpg

Bad Speaker....
https://dl.dropboxusercontent.com/u/...2014.20.32.jpg
Old 19th September 2014
  #2
Lives for gear
 
LeeYoo's Avatar
 

Hi.
I don't see any bad capacitors in your pictures.
Just a few glued together with black goo, to stop from dancing to the bass and breaking their legs.
Some monitors do have issues with connectors.
Check that first, by removing/inserting each connector on the board a few times.
Tweeters (and woofers) can be measured with a DMM. About 5ohms is ok.
Leo..
Old 19th September 2014
  #3
Lives for gear
 

i dont think this is black glue. but serious fire damage. why would they use black glue on one channel only (the other channel looks perfectly clean)? also there is no need to fixiate a radial capacitor in this case. it will sit there perfectly fine. these caps look totally f*cked to me. i would replace them all. just my humble opinion. also check all surrounding parts.
i dont see how anybody would use "glue" to hold them together. that doesnt make any sense looking at the pcb.
Old 20th September 2014
  #4
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LeeYoo's Avatar
 

Looking at the pictures, it looks like glue to me, but I could be wrong.
Stuff from leaking capacitors is usually brown.
It if comes off with alcohol, then you can be sure it's from the cap.
Black rubbery glue only lifts off with acetone.
Leo..
Old 20th September 2014
  #5
Lives for gear
 
Radardoug's Avatar
 

Why are you people so fixated on capacitors? I agree with Lee, glue holding them together.
KRK's are notorious for connector problems. Check the input connectors, if they are IDC Molex then solder them up.
Also the power connectors on KRK's will cause low level hum when the IDC connectors fail.
Old 20th September 2014
  #6
Lives for gear
 
S2udio's Avatar
 

As already said .....its glue ,all manufactures do it....esspecialy in active monitors,
There is more at fault here than the caps, which i bet are fine,more likely connectors or dry joints
Just randomly replacing caps will get you nowhere,
I always start by a good re wet of all the pcb connectors and power traces,
From there on if no joy ,its out with the DMM ,to fault find at component level....
A good working knowledge of what the circuit is supposed to do helps !
Old 21st September 2014
  #7
Gear Head
 

Yeah I took it into an electronics tech in my area who has 40 yrs + experience / does a lot of tube gear and seemed pretty knowledgeable. He also said that it seemed like it might just be the goo & not a blown capacitor. He was confused as to why they just did one monitor though. Should be hearing back about what other issues he finds tomorrow. Can update on what happens if you guys are just curious.
Old 21st September 2014
  #8
Gear Maniac
 

Elcaps have a pre weakened spot to let the pressure out if it blows: that is the cross you see on the top. With that in mind it becomes even more unlikely that the black stuff is has emanated from the elcaps.
Old 21st September 2014
  #9
Gear Head
 

So the electronics tech checked it over... Definitely was just goo. He checked a bunch of connections & resoldered some things. No luck, Appears to be some component in the tweeter amp that has gone wrong and he cant do anymore without schematics.
Anyone have some vxt 8 schematics or know somewhere to buy parts like a new tweeter amp? (fingers crossed)
Old 21st September 2014
  #10
Lives for gear
 
Radardoug's Avatar
 

Tell your tech to check the rails, particularly the rails generated for the opamps. They use very small bypass caps which fail, and take out the series droppers for the +/- 15. Its fairly obvious which bits, 2 watt resistors by the main supply caps.
Old 29th January 2017
  #11
Here for the gear
 

hi there, curious if you ever found a solution to this problem? I'm having a very similar issue with one of my VXT4 monitors
Old 15th March 2017
  #12
Here for the gear
 

Hi guys,

One of my vxt8's is experiencing the same issue. I'm curious to see if this problem fixable or if a new amp is needed (which are impossible to find in the U.K.). I may just end up buying a new moniter on eBay as they have come down in value substantially recently. Oh also the Gibson support centre was useless.
Old 3rd February 2018
  #13
Here for the gear
 

Red face

I know this is an oldish thread I have had same issue for some time which went away after the monitor appeared to warm up, and I could live with it. About 3 months ago it became persistent and incredibly loud, as I wasn't working on any projects at the time I just stopped using my monitors(VXT8). I found a post on the Cakewalk forums
from a gentleman with the same issue from a KRK Rockit 6 that turned out to be filter caps in the power supply which caused damage to related resistors. He was thoughtful enough to include the link below to an mp3 of the crackle.

http://www.efextek.com/cakewalk/krk-static-pops.mp3

Below is the link to the post.

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

I will be looking at the corresponding components in my VXT8s and verify if this fixes the issue.

Last edited by etwolf; 3rd February 2018 at 10:29 AM.. Reason: bad composition.
Old 5th December 2019
  #14
Here for the gear
 

Seems there are ongoing issues with these products. I have a huge hum problem with a vxt4. Currently seeking schematics to try and sort it.
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