KRK RP5 Rokit G2 | Death by black gunk | BOM plus tips 'n tricks?! - Page 1
Forum section: electronics / repair

author: relativ
author_rank: Newbie
timestamp: August 23, 2025, 01:54:08 pm
content: Hey everyone,both of my KRKs (RP5 G2) have been making a booming noise when switched on for a long time, and one of them had quite a hissing sound. Now, the woofer on one of them has become very quiet and then failed completely. The tweeter still seems to be working, but it is very quiet.So I googled it, looked around on YouTube, and of course it didn't take long before I learned about “death by black gunk.” That's how I came across a thread on gearspace the EEVblog repair videos and in the end this forum, and I decided to register here to get some valuable tips.I've already started removing as much glue as possible. However, some areas are quite difficult to reach, so I'll probably follow Squirralex's (from gearspace) tips for first-time glue repairers and unsolder the capacitors first. Here are his general tipps:"- Go for it, you can do it!- De-solder all the lerger caps and detach the cooler from the amps and board (See how much goo is inside the amp that you would otherwise not be able to reach- have a proper pick with a fine tip to go under components- Go for it, start wherever you feel like and just rotate the board as long as there is stuff to clean- roughly pick away crust, vacuum off, pick more thorough and go in with acetone Q-tips in between- don't be lazy"Also helpful I found "Amp Mechanic" with his Video on Youtube, where he ist "Fixing a KRK Rokit 5 RPG2 Monitor Speaker". (Don't know wether external links are welcome here?!) And I add the "KRK Rokit 5 powered studio monitor speakers repair" from "FeedbackLoop" which I just found and think is quite helpful.I found plans for the amps online, but they are quite illegible. Does anyone have any that are easier to read or know where I can get the right plans? While scraping the circuit board, I've already damaged some of the labels, and some capacitors and resistors are completely covered in goo, so I can't decipher anything to buy replacement parts.Speaking of replacement parts: On the gearspace thread saw a recommendation for carbon film resistors. Are they a similiar size - just want to be sure that they are fitting the PCB. Are there any recommendations for high-quality capacitors? I guess Panasonics or nichicon? I would like to order everything from DigiKey in one go. (Or would you recommend another provider?) Maybe someone already wrote down a bill of material (BOM) - if so, I would really appreciate it if someone would share the list. For example like for all bigger capacitors, which are:2200µF 50V2200µF 50V1000µF 35V1000µF 35V220µF 16V220µF 16V100µF 25V100µF 25V47µF 50V47µF 50V47µF 35V10µF 50V10µF 50V10µF 25VMaybe someone already has a list for the resistors or diodes etc. I might link the components on a picture to a text, so in future it's easier for non-electritians and myself to find the right replacement parts.I've attached a few pictures of the current status of the preamps and the normal amps (and the plans I found online). I probably need to be more patient and scrape everything off better, right?Or is it hopeless because the circuit board might be damaged? Bobby Baird at gearspace, for example, designed a completely new PCB and assembled it himself. Unfortunately, I don't have the necessary knowledge to do that. He even has a few circuit boards left over, but a) his PCB is for the Rokit 8 G2 and b) he lives in Texas. Has anyone in Europe ever designed a PCB for the Rokit 5 G2?Sorry for the wall of text. I appreciate any help. And of course I'll keep you updated.

author: Swake
author_rank: Frequent Contributor
timestamp: August 23, 2025, 08:40:54 pm
content: Quote from: relativ on August 23, 2025, 01:54:08 pmThat black stuff might have turned conductive over time. Elbow grease and a lot of patience is what you need.Quote from: relativ on August 23, 2025, 01:54:08 pmThe bigger ones (+/- 1 cm) are 1/4 W resistors, the smaller ones (5 mm) are 1/8 W resistors. Their size is standardised. Metal film or carbon film, it doesn't matter in this application.Ones you have removed the glue you'll have to ensure that the speaker is repaired. Just swapping stuff might or might not repair it. Anyhow I'd suggest to only change what is effectively broken or cannot be salvaged due to the glue. And of course you'll have to swap that part in both speakers to keep them 'aligned'.Quote from: relativ on August 23, 2025, 01:54:08 pmIf the copper tracks are damaged you'll see it. You can always repair that with a piece of wire.

author: rvalente
author_rank: Frequent Contributor
timestamp: August 24, 2025, 01:02:29 am
content: Id start with a good soapy water scrub, get an old tooth brush, some neutral dish soap and some elbow grease, be thorough. Put it to dry on some warm place, after it looks dry, wash again with isopropanol, let it dry again.

author: Swake
author_rank: Frequent Contributor
timestamp: August 24, 2025, 06:13:55 am
content: Quote from: relativ on August 23, 2025, 01:54:08 pmHad a quick look. He also made a lot of changes. For example the original power supply transistors are 3 Amps capable, he replaced that with a LM317/LM337 combo that is max 1.5A _if_ they are cooled, but these are in the middle of the PCB without heatsink. This means the power output will be way less, especially noticeable on the low end. There are also changes on the preamp and amp design. That new PCB is not going to have the original sound at all. No one can tell if that new combo is any better or works as you intend it.

author: relativ
author_rank: Newbie
timestamp: August 24, 2025, 02:39:39 pm
content: Quote from: Swake on August 23, 2025, 08:40:54 pmYes, I guess. Unfortunate. An such a shame KRK used this.Quote from: Swake on August 23, 2025, 08:40:54 pmQuote from: rvalente on August 24, 2025, 01:02:29 amSo I decided to remove the cables for LF and HF and removed the for bigger capacitors to have an easier clean. Afterwards I tried to remove as much of the black gunk as I could. Then scrubed everything with a tooth brush and some isopropanol.You can see the current state in the pictures attached.I would really appreciate if you would give your two cents about what components (jumper, capacitors, resistors,..) to change. Hard to tell from pictures - I'm aware of it. But might help as a confirmation in my thinking process.And can you recommend any "glue" for electronics that is not getting conductive over time?Imho no capacitor is bulky/curved. Some jumpers look like there is corrosion. Some resistors were covered in black goo and it's hard to tell wether it had any influence.. probably just replacing 'cause they are cheap anyway, right?Have a look at the pictures attached if you like.Still really appreciating any help! <3

author: Swake
author_rank: Frequent Contributor
timestamp: August 24, 2025, 03:27:46 pm
content: You might want to replace the resistors that have chipped paint. The beige ones are about the cheapest carbon film you can find. In general, it seems they used the cheapest components one could find.R103 - note that it is mounted about 5 mm away from the PCB, this is to facilitate airflow and heat dissipation. If you replace it make sure to put it back at the same distance.The small blue ones named RL### are likely coils, not resistors. Better to replace the one on the left bottom.The 2 caps bottom right still seem connected with that gunk.The tin coating on the jumpers is partially gone, but you should not care all too much about that in this stage.It is a single side board, all copper traces are on the bottom side. The black print on top has no function other that to inform about the traces, in other words: don't worry.Put that thing back together and see if you have again sound from the low end speaker. If it works you can still evaluate if you want to invest in improvements or not. If it does not work you'll have to find what is wrong first.

author: relativ
author_rank: Newbie
timestamp: August 24, 2025, 05:17:19 pm
content: Quote from: Swake on August 24, 2025, 03:27:46 pmI have a basic multimeter - resistors I measured seem fine so far compared with the target value (TV):R100/R101 are 1.9kΩ - (TV: 2.2kΩ)R103/R104 are 46,9Ω & 46,7Ω - (TV: 47Ω)R105/R106 are 2,94kΩ & 2,95kΩ - (TV: 3kΩ)R107/R108 are 1,96kΩ & 1,97kΩ - (TV: 2kΩ)R109/R110 are 2,17kΩ & 2,16kΩ - (TV: 2,2kΩ)But I might replace them with better ones, because they aren't to expensive anyway.Quote from: Swake on August 24, 2025, 03:27:46 pmThere are some looking like normal resistors but are named RL too. What are these? Coils or resistors?And yeah - the one on the bottom left will be replaced.Quote from: Swake on August 24, 2025, 03:27:46 pmThank you for pointing that out. I guess the same probably applies to R104 then, too. I will do it that way.Quote from: Swake on August 24, 2025, 03:27:46 pmYes. When I got rid of the black gunk with a tweezer I scrathed the jumpers too. The parts that look like copper now were parts where I saw some corrosion.Quote from: Swake on August 24, 2025, 03:27:46 pmOkay perfect. Then I won't worry about it anymore.Quote from: Swake on August 24, 2025, 03:27:46 pmI once did it before I de-soldered the big caps. The low end worked, but the tweeter didn't seem to. And then the volume seemed to drop.BTW: I measured the big caps I de-soldered. Unforunately I have no ESR-meter or any way to measure capacity, but when doing resistance measuring the resistance grow. On every cap. So it seems like my assumption was right. None of the caps is "dead". I don't know wether they are precise, but they all seem working which is matching with none of them bulking.______________I'm a little worried because my soldering iron didn't work to well when desoldering. Probably because I didn't use flux paste? So I had quite long contact and I'm a bit worried the caps could have taken damage. On the other hand I did the measuring afterwords and everything seemed fine.Now I'm thinking like I have two options:A) Could just replace any Caps and a few resistors and coils(?!) which where covered in goo and hope for the best?orB) Before that or any repairs -> find out if something and what is wrong first? But in this case: How do I find out what's wrong?

author: Swake
author_rank: Frequent Contributor
timestamp: August 24, 2025, 05:39:46 pm
content: Quote from: relativ on August 24, 2025, 05:17:19 pmB is the correct choice.If something is wrong we'll solve that problem when it presents itself, hopefully we can. At this moment you don't really know if something is still wrong or was ever wrong besides that conductive glue. You might replace a lot of things and still not have a working device. Let's be optimistic and try first.Should you be very unlucky and there is smoke make sure you know where the smoke is coming from before cutting off power (am not joking).The solder is not melting when the contact between soldering iron and tin is not good/large enough. This is happening all the time. By adding some more solder you make the contact better and the thing starts melting. It sounds counter productive because you unsolder, but that is how it works. You can improve contact with flux too.Measuring caps with an Ohm meter does not indicate if these are still good. Yes, there is some capacitance left, but it cannot tell you how much. For now, don't worry.Before power on, double check all connections, dust, solder, and so on. Don't connect you expensive audio equipment at first. First measure the power supplies to see if the values make sense. Check if nothing becomes very hot. Touch with a wet finger, if there is steam, it is too hot (this time I'm joking, but only just a bit as this would work actually).Good luck.

author: relativ
author_rank: Newbie
timestamp: August 24, 2025, 09:10:43 pm
content: First of all: Thank you for your patience and the guidance. I really appreaciate it!Quote from: Swake on August 24, 2025, 05:39:46 pmYeah. I mean you are right. I was just thinking about replacing the caps anyway. But obviously it is not worth the change if the speaker still won't work afterwords.Guess I need to stay patient.Quote from: Swake on August 24, 2025, 05:39:46 pmTalking about smoke. For quick testing it's okay to not reattach the cooling block, right?Quote from: Swake on August 24, 2025, 05:39:46 pmYes, I had read that. Unfortunately I don't have any flux paste. But I think I might have some solder with flux in the core. Going to search that before resoldering the caps.Quote from: Swake on August 24, 2025, 05:39:46 pmYes. I just wanted to make sure they weren't dead.But I might get equipment at a repair meetup to measure the capacity of the caps. They might even have an ESR meter, which would be fantastic. But as you said. For now there are other things to do.Quote from: Swake on August 24, 2025, 05:39:46 pmMy plan is to:1. Turning speaker on without signal.2. Measuring wether there is any DC voltage at line in.3. Use inexpensive audio equipment to provide a signal with low volume and then slowly turning it up. (But what? Don't know wether I have anything like an old mp3 player. How high is the risk to actually damage the interface?)What values should I expect?And do you mean to measure supply voltages? I'm a little scared since mains voltage is 230V and I really should only measure secondary voltages, right?So plan would be like:1. Set the multimeter to DC volts.2. Connect the black test probe to ground (GND) or the negative terminal of one of the large electrolytic capacitors.3. Connect the red test probe to the positive terminal of the electrolytic capacitors.I'd rather ask one more time. When the device is turned off, I'm not too worried, but when it's turned on... it's a little more threatening.Or should I wait with that and ask for help at the repair meetup?Edit: Before that I might have a look at the crimp connectors. On gearspace someone called "Radardoug" mentioned that:"The power connectors are a crimp type connector that fails. Open up the speaker, there are two amplifier cards, and a harness that brings the power onto the card. This is the source of the problem. Solder these connector pins to the wire, and the problem will go away. The problem is caused by the fact that the main filter caps charge by drawing a very high current on the peak part of the power wave. Any resistance in the ground side allows this peak current to intoduce buzz into the ground side of the supply."Which a) sounds logical to me and b) is supported by the experience of one user who had a humming noise that just went away after he opened and reassembled the speaker.Question is: Does he mean solder the "crimp" connection of the LF and HF cables to the cables? Or what does he mean exactly? I don't get it.(Think I get it now. Saw a post of him later. So I guess we are talking about the white plastic housing with the 5 metal contacts and the counterpart at the end of the main power wires. Correct?)In a later post he explains:"You will see wires going to the pcb. At the pcb is a plastic housing containing metal contacts. These press against pins mounted in a plastic housing on the pcb. Follow the main power wires to the pcb, and voila! There is the crimp connector. This connector is similar to ones made by Molex, formerly Utilux. If you look in the top of the connector, the wires are pushed in and engage with the contact, but this engagement is not very solid. You can poke a soldering iron in there and solder them. It is very messy, but possible."Not sure wether I want to go that messy way. But in the worst case scenario where the speakers just won't work properly, it could be a last resort.Quote from: Swake on August 24, 2025, 05:39:46 pmThank you! <3

author: Swake
author_rank: Frequent Contributor
timestamp: August 25, 2025, 08:38:17 am
content: You'll have to jump over the fear level of measuring stuff that is powered on. Evidently you'll have to be extra careful not to touch mains. Put on plastic/latex/nitrile gloves if you really are afraid. These will not save you from a stupid move but it gives some extra confidence.So yes, you measure the power supplies on the so called secondary side. That is low voltage only. I cannot read what is written in the schematic but one can see there is a regulated power supply (see attached, upper part, for the pre-amp I think) with -/GND/+ and a second unregulated one (bottom 2x C + 2x R + 4x D, probably for the power amps). The ground point for both (left bottom) is where you want to connect the GND probe of the DMM. The negative and positive power supplies should have a value in the same ballpark. Like -8 V and +8 V. And -20V and + 20 V for the other one. These are not the real numbers, only an example for illustration of what to expect.If there is something missing: double check and report.After that you can measure DC on the speaker out. That is a good idea. Should be 0 V or very very close.Don't change anything in those connectors, certainly not goofing around with a soldering iron in them because you'll brake it of. Eventually with no power applied you can measure conductivity with the resistance Ohm setting of the DMM. You should read very low resistance like 1 Ohm or less.Replacing components will require to add solder (with flux).

author: relativ
author_rank: Newbie
timestamp: September 15, 2025, 01:27:48 pm
content: I'm not gone - just waited for the repair meetup.Unfortunately the first guy couldn't help much, but he made an effort to ensure that another person helped me in the end. The new guy soldered out a small power amplifier and re-soldered it. I tried to resolder the large caps, because at home I produced some cold solder joints. Although I used some flux I kind of had to go for 450°C at the soldering station and still I took some time. He improved some of them too.In the end: Tweeter is still pretty weak and the woofer is quiet. -> But yeah, no time for real repair. So not a surprise.But: He touched the board and measured some stuff and said the amplifier board (where all the gunk was, which I cleansed) seems fine. So I still have some hope. It might be a problem with some components, probably capacitors, he said.Now I'm thinking to go for strategy B and just buy some components. Go to the kind of "nerd version of the repair meetup" and hope, that someone with soldering experience helps me soldering some new and better capacitors as well as some resistors.I mean I could ask wether they would help me measuring the power supplies but I couldn't tell them what they should measure. Except the values you mentioned.

author: Swake
author_rank: Frequent Contributor
timestamp: September 15, 2025, 02:23:12 pm
content: I guess it is time for you to purchase your first multimeterHere some cheap examples, certainly not top class Fluke or Agilent meters, but surprisingly good nevertheless. I throw one of these in my car or bag anywhere I go as a 'consumable'.Digital Multimeter ZT100 (less than 15€ on aliexpress, delivered...)ANENG AN8008 (about 25€)ANENG AN8009 (usually 30€ but just found it for 18€ in the bundle deals)ANENG AL01 (about 16€) measures inductance too.Search for 'soldering exercise' on Ali and you will find tons of cheap kits to learn soldering. Can be a fun time too.Maybe also a roll of 0.5 mm or 0.8 mm solder with flux core. Don't buy the really cheap ones as those are anything but solder. Also don't hesitate to take solder containing lead (lower melting point than the new stuff and it makes a big difference for a beginner as it will make your life so much easier), no, it will not kill you unless you proceed to eat the entire role raw and then some. This is the right alloy if you want to avoid cold joints: 63% tin/37% lead (63/37) - I personally use 60/40 because I have a bog stock, but while it is still very useable it is somewhat more delicate to work with. If the alloy is not written on the roll it generally is crap stuff.