Monitor falls in and out, odd issues

Hello.

I hope that you're able to assist with this odd problem I'm having with my pair of KRK Rokit 5 G2 monitors.

For a few months the right monitor has had an issue with stopping working, either it plays extremely low and with a lot of crackle, sometimes it just flat out stops playing, the light is still on at all times.
After a few weeks I noticed that it sometimes has to warm up when being turned on. I just have to play some audio for a few minutes, it will crackle a bit and then play fine. Sometimes it will do this as well even if no sound is playing. Crackle a little bit. It seems to 'warm up' easier when I'm playing some audio with a lot of constant low-end, Thomas Köner's work has done wonders for this purpose.

One particularly odd thing that I can't make sense of, is that if the monitor stops working, simply changing the cables, right to left, left to right, seems to make it work most of the times. This will solve it temporarily and works fine when I change the cables pack to their proper positions. I have no idea why. I'm using a Steinberg C1 USB interface, I haven't had a chance to test if that might be the problem, but I doubt it since the monitor itself will crackle at times when not plugged to the computer via USB. I've tried with RCA and XLR cables as well, it doesn't seem to make a difference.

Thank you in advance.

M

Sounds like something wrong with the crossover in the right monitor, or something broken on your C1. Have you opened them up to take a look?

You've changed nothing else in your physical setup?

I wouldn't quite know what to look for inside the monitors. I've never had them open.

No, nothing has changed for some time. I just started happening one day out of the blue.

Maybe there's a dry solder joint somewhere in the electronic gubbins - you having to 'warm it up' may be that it's getting warm enough to increase the conductivity allowing the current to flow through the dodgy joint.

mcbpete, that sounds plausible. I seem to remember it going dead when playing at low volume, I assume it could be connected. Would that perhaps explain why it would work for a while when swapping the cables? That a small sudden burst will allow the current to flow temporarily?

Quite possibly, I'm no electronics expert but I worked in an electronics goods shop for a year or so (though as a delivery, fitting and sales person) and any time there was 'crackling' or 'warming up' mentioned the first things the repair guys checked for was dry joints.

  On 3/16/2015 at 6:52 PM, mcbpete said:

Quite possibly, I'm no electronics expert but I worked in an electronics goods shop for a year or so (though as a delivery, fitting and sales person) and any time there was 'crackling' or 'warming up' mentioned the first things the repair guys checked for was dry joints.

should be easy enough to spot with the naked eye

Will looked cracked or depending what's soldered, maybe bent or have a line through it... I think?

  On 3/16/2015 at 7:00 PM, StephenG said:

Will looked cracked or depending what's soldered, maybe bent or have a line through it... I think?

I took it apart to have a look. The inputs were hard to get to and more or less enclosed, so I have no idea about the soldering, I didn't feel I knew nearly enough to take it apart any further.

But I did notice a lot of black rubbery goo on certain parts of the board. It seemed like it was put certain places to glue together parts, but it flowing all over everything is hardly a good thing. A few slightly bent capacitors, not bulging, still connected as far as I can see. Nothing seemed fried or broken, but that goo.

The photo below shows the goo in red circles and bent capacitor in green.

I think the 'black rubbery goo' is epoxy resin - It's usually to protect components so I don't think that's a problem...

I see. It just look very odd. Especially with the small bent parts being covered in it. But thank you both very much so far.

does the crackling intensify if you jiggle where the cable plugs in to the speaker? it could be the jack is loose.

Not at the inputs for the external interface, but I just tried pushing down lightly on the jack that enters the monitor itself, and that will immediatly cause the signal to stop. It will come back as soon as I don't apply pressure anymore. Faulty jack socket?

Sounds like one of the solder joints connecting the jack to the board has cracked/come loose. The reason switching cables works is because you are fiddling with how the jack is seated and creating a better connection. Next time you run into this problem, try just jiggling the plug in the jack and see if that 'fixes' it. If you do this a lot tho it will loosen the jack more making the problem worse over time.

The good news is that it's easy to repair, you just need to resolder the joints for that jack. If you don't feel comfortable doing this yourself, maybe you know someone who can solder? It should only take about 10 mins to properly fix!

That's good news. It's seems to enter various states, where it will react to certain things. If it's just completely off at the start of a session, it usually has to warm up, with or without signal, and at this point no cable fiddling will have an impact. When it has 'warmed up' it will fall in and out as said, here it will respond to cable fiddling on on most occasions, swapping cables and what not. Some fiddling will produce the occasional crackle and noise, but not much. Fiddling a bit will sometimes help get back the signal temporarily, but it doesn't seem to be very reproducible.

I've tried to have only the faulty monitor on and raising the volume louder and louder, at a certain point it's producing a hissy and crackly signal and will 'break in', like it the signal level will warm it up again and it will go back to a more suitable level, though still with hiss and crackle.

When I took it apart it seemed that the jack section was enclosed in a box, that I couldn't seem to get to at first glance. I'll have to open it up again to see. I've got no soldering skills, but if it seems like an easy fix I can probably manage with a little dedication. Thank you.

I'm guessing from looking at an image of the rear of the speaker that this pink circled section is the solder joints for the trs jack (assuming you are using trs).

Another thing to check would be that the cables themselves aren't problem! Try and different set of cables...

Also next time the problem occurs see if moving the volume knob around fixes it. Does the volume knob crackle when it's adjusted? It could be that dirt in the potentiometer is causing a bad connection and giving you improper resistance, sending a signal to play at low volume.

Yes, those are the jacks, the above three are for xlr. I'm learning as I go along here, so excuse my possible misunderstanding of your advice and directions.

The section of solderings on the right of the jack, your pink circle, seems to be a bit dull compared to the others. It reflects a lot less light. The photo above doesn't show it very well. Though a bit.

There are three solderings forming a vertical line in that picture near the end of the board, the third one is significantly more bland and unreflective compared to the other two. None seemed be downright cracked or broken, some had very small lines in them, but they follow the board print pattern, so I assume it's of no big significance. Though one of the solderings in the vertical line (the one on the top) seems to have a slight crease at the bottom, curving inwards. I have no idea how much disturbance a soldering needs to not be able to flow correctly.

And I've tried a lot of different jack cables, all the same crackle. I have tried fiddling with the volume meter on the monitor itself, and it would react crackly when being turned up, but it seems to be the same reaction as is the volume was raised on the external soundcard.

I tried jack to RCA cables again, no very apparent crackle as the jacks, but a slight hum and a comparably lower signal. I have to turn up to the point of distorting the sound if I am to reach anything close to the left monitor. I tried turning the gain knob, -3db to +6db, on the back of while testing. It will react, but seems to be swallowed by hiss when gained back and forth, which almost sounds like an extremely unsubtle and hard compression. I assume it's a reaction to the movement. I tried tapping the knob with varying amounts of pressure, it produces same results. Rocking it lightly seemed to create the same effect as with applying pressure to the jack cable.

You should probably be careful not to have the volume cranked too high in case the connection is restored and it blasts at full. If both the RCA and TRS jacks are affected then it's likely something other than those. Maybe the volume pot? You could try spraying contact cleaner into it and see if that changes anything.

There's a thread on KVR in which a person having a similar problem to yours fixed it by repairing cold joints. Sometimes they can be hard to spot and even dull looking solder joints can often have fine connections. afaik the dull solder is just an indication that the solder didn't achieve a high heat which could indicate it didn't flow into the joint nicely. There's some helpful pictures if you search 'cold solder joint on google images.

It's probably something simple like this which is easy to find and repair if you know what to look for, but it can be frustrating and time consuming if you are unsure :(

I've tried checking the soldering for the potentiometer, but there are some soldering sitting beneath a foam-clad box that seems to hold the RCA input. It also has the protective black substance on the edges that connects to the back.

When inspecting the soldering again I did notice that most of them seem dull and non-reflective, but only one had any noticeably different appearance:



Would this be enough to disturb it?

I bet it is, but I've got no clear image of what may be the problem, so I really appreciate all of your help.

I also have these monitors (as so many people do) and I'm pretty sure one of it sometimes switches the high frequencies off. Or it's my music with way to weird panning

It is now in even worse shape, most likely due to my constant fiddling. There is no warm up or anything, it doesn't regain volume or signal stability by itself and hasn't for three days. The only way to get volume spikes is to turn and apply pressure to the volume pot on the back of the monitor itself, but will mostly stop when not applying pressure, sometimes it sits in a sweetspot and seemingly play fine before a small movement will break up the signal.

Applying pressure to it was the same I did with the trs jack, but now it seems to be the volume pot. Whatever it is, something is wrong in that region.

I'm cautious of fiddling more as I'm afraid I might cause more damaged to what seems to be a rather simple solder-fix. Any more suggestions?

It's up to you at this point. Have you ever soldered before?

It's not rocket science... I'm sure you could figure it out from watching youtube vids. That being said there is a potential for burning the board/melting components in you are very uncareful. Personally I would say go for it, as the best way to learn imo is just to mess up until you get it right. But you could also just take it in to a professional and maybe spend $50/$100 and get it back in tip top shape.

A number of the joints in that photo look like they could be dry, especially the bottom row!

Once or twice years ago, guided circuit bending. That's true, I will give it a go. I just want to make sure what the problem is before I start trying to fix anything.

Right now the pot is in a sweetspot, it doesn't seem to react too good to sub and low frequencies. Moving the pot up and down will make it crackle and create a sound which sounds quite a lot like proper vinyl scratching.