Replace caps in active monitor

[kininigin]

I decided to be nosey and poke around in my active monitors to see how they are put together and what parts they use.

Upon opening up the back/heatsink,i noticed that a couple of caps are leaking and left a burnt residue over the pcb and other parts.

This is a budget monitor so the parts inside are probaly on the cheap side of cheap(although i have no real clue how good or bad they are).I would like to replace some parts and would like some help in choosing what to get.

Here is a picture of the amp board,which is not a picture of my monitor but has been taken from another source.

http://i1135.photobucket.com/albums/m639/kininigin/TapcoBack.jpg

If you look at the right hand side below the large cap,there is a smaller one which seems to be leaking,this is where the rca input is as well.

The large caps values are 6800uF 50v,the one which is leaking is 470uF 25v and there are a couple more i can see which are,47uF 25v.

Would it be possible to replace the transformer with a better quality one?

Here is a link to the one in my monitors http://www.mackie.view-media.be/order/index.php?item=part_-_-150-r0704501-e&action=article&group_id=10000023&aid=489&lang=EN

I would also like to replace the rca input and the iec input to something a little more robust.

Here are the schematics http://theartofsound.net/forum/attachment.php?attachmentid=3962&d=1300226829 and http://theartofsound.net/forum/attachment.php?attachmentid=3963&d=1300226856

[kininigin]

I have been looking on the net for suitable caps and found these

http://www.hificollective.co.uk/components/nichicon_kg.html

NKG-200 - 10000uF 50V Nichicon KG Type, Gold Tune, lug

Would this particular one be a good replacement even though it has a higher Capacitance figure of 10000 uF rather than 6800uF?

[Puffin]

Are you sure it is leaking and not some gunk put on it for stability?

[kininigin]

Are you sure it is leaking and not some gunk put on it for stability?

Im pretty sure,as it looks like it has dribbled down the cap and spread about abit on the pcb,having said that the monitor still works with no ill effect.

Is this common to put ''gunk'' on for stability.?What ever it is,it has gone all dried and burnt and looks plain wrong.

I'll check the other monitor tomorrow,to see if that is the same.

[DSJR]

Being cautious, I'd probably uprate the voltage rating from 50V to 63V and 25V to whatever the next rating upwards is. Cannot comment about the value, although 6800 to 10000 shouldn't be an issue.. Hope someone better qualified can assist you :)

[kininigin]

Being cautious, I'd probably uprate the voltage rating from 50V to 63V and 25V to whatever the next rating upwards is. Cannot comment about the value, although 6800 to 10000 shouldn't be an issue.. Hope someone better qualified can assist you :)

From my limited understanding,i think your right and a slightly raised value shouldn't be an issue.

Im not sure about raising the voltage though,would it not be safer to keep it the same?

[StanleyB]

10,000uF would be better.

[kininigin]

10,000uF would be better.

would raising the voltage as dave suggest be better as well?

Also the other caps have value of 47uF and 470uF,would i need to raise these as well if i went for 10000uF rated caps?

[StanleyB]

You would have to measure the voltage at the output of the bridge rectifier in order to see if the rectified AC exceeds 50V. If it is say about 56V then the caps rating of 50V is fine. If the rectified voltage is more than 45V then go for 63V power caps. The reason for all this is that the mains is not 240V, but can be easily 10% higher. So the caps working voltage has to be able to handle the 10% increase.

As for the other caps: stick to their value or go 50% higher.

[kininigin]

You would have to measure the voltage at the output of the bridge rectifier in order to see if the rectified AC exceeds 50V. If it is say about 56V then the caps rating of 50V is fine. If the rectified voltage is more than 45V then go for 63V power caps. The reason for all this is that the mains is not 240V, but can be easily 10% higher. So the caps working voltage has to be able to handle the 10% increase.

As for the other caps: stick to their value or go 50% higher.

Ahh i see,that makes sense now.I was going to get my mate to check things over with a meter but i would like to learn how to do things myself so appreciate the help stan :).

I can see a few more questions being asked over the next week or so :lol:

Can someone reccomend a multimeter to get me started? Nothing to fancy,just something that will get the job done.

[StanleyB]

You would have to measure the voltage at the output of the bridge rectifier in order to see if the rectified AC exceeds 50V. If it is say about 40V to 45V then the caps rating of 50V is fine. If the rectified voltage is more than 45V then go for 63V power caps. The reason for all this is that the mains is not 240V, but can be easily 10% higher. So the caps working voltage has to be able to handle the 10% increase.

As for the other caps: stick to their value or go 50% higher.

Info updated.

[StanleyB]

Can someone recommend a multimeter to get me started? Nothing to fancy,just something that will get the job done.
I have one of my field service multimeters that I was going to put up in the classified for the cost of P&P. PM me with your address and I'll let you know how much it cost me to post.

I'll try to take a pic of it later today after work so you

[kininigin]

I have one of my field service multimeters that I was going to put up in the classified for the cost of P&P. PM me with your address and I'll let you know how much it cost me to post.

I'll try to take a pic of it later today after work so you

Quality,cheers stan,i'll send you my details.

[kininigin]

Are you sure it is leaking and not some gunk put on it for stability?

I checked the other monitor today and i think you were right,it seems to be some sort of glue which has discoloured and burnt due to heat from the caps.

So no danger in losing use of my monitors,well that is until i get my grubby little mits on them and try to upgrade them :lol:

[worthingpagan]

I checked the other monitor today and i think you were right,it seems to be some sort of glue which has discoloured and burnt due to heat from the caps.

So no danger in losing use of my monitors,well that is until i get my grubby little mits on them and try to upgrade them :lol:


Let us know how you get on please Darren, i'm looking at having a go myself, once i've sorted the house insurance :lol:

[kininigin]

Let us know how you get on please Darren, i'm looking at having a go myself, once i've sorted the house insurance :lol:

Will do mark,i dont really know what im doing so will be taking it slow and steady.I'll be putting my limited soldering skills to the test,lets hope it doesn't go tits up :lol:

[DSJR]

Caps shouldn't get hot, is my recommendation, as the hotter they get, the shorter their life - well, electrolytics anyway as I understand it..

The "goo" which holds them in place should ideally be carefully scraped right back, as my own CD player was dealt with thus and it had bad side effects after twenty years. There's a thread about it somewhere with pics.

To be honest, the speakers you have a pretty new aren't they? if they're made in China, it wouldn't hurt to replace them with better quality items as much has been said on t'internet regarding fairly recent Jap made Quad 909's and their currently? inferior (and audible) distortion performance these days compared to early ones. The 909 also has the Quadlink bits which apparently should be removed, but that's for another time..

Good luck and TAKE CARE with your soldering, as a botched solder job will remove any potential advantage regarding the superior components you're hoping to fit.. ;)

[Puffin]

Is that you as a "hoodie" frightening the other skiers:lol::lol::lol:

If you are able to take some close-up pics of the actual caps you intend to replace it would be of help. Bear in mind that what you are proposing ot do may make no difference to the sound quality.

[kininigin]

Caps shouldn't get hot, is my recommendation, as the hotter they get, the shorter their life - well, electrolytics anyway as I understand it..

The "goo" which holds them in place should ideally be carefully scraped right back, as my own CD player was dealt with thus and it had bad side effects after twenty years. There's a thread about it somewhere with pics.

To be honest, the speakers you have a pretty new aren't they? if they're made in China, it wouldn't hurt to replace them with better quality items as much has been said on t'internet regarding fairly recent Jap made Quad 909's and their currently? inferior (and audible) distortion performance these days compared to early ones. The 909 also has the Quadlink bits which apparently should be removed, but that's for another time..

Good luck and TAKE CARE with your soldering, as a botched solder job will remove any potential advantage regarding the superior components you're hoping to fit.. ;)

It was a very uneducated guess,that the caps were getting hot.Something is as the glue? is looking burnt.
I think they were made in the US by Mackie which is a well known studio monitor manufacturer,but don't quote me on that.

On the soldering side i think i will practice on some boards first rather than jump straight in.I don't want to be without speakers right now as i cannot afford any decent new one's.

[kininigin]

Is that you as a "hoodie" frightening the other skiers:lol::lol::lol:

If you are able to take some close-up pics of the actual caps you intend to replace it would be of help. Bear in mind that what you are proposing ot do may make no difference to the sound quality.

not sure i get the ''hoodie'' ''skier'' reference :scratch:

My camera is rubbish so close ups are a no-no.,
On the first page you can see the large caps which are G luxon's with value of 6800uF 50v,im not sure what the others are but look like thet could be the same make.

I have no idea if changing the caps will improve sq,so theres only one way to find out i suppose

[Puffin]

Sorry, I assumed that moutainhighseasons was your business:(

[kininigin]

Sorry, I assumed that moutainhighseasons was your business:(

Ahh i see,I forgot i had that link in my sig :doh: Your close,it's my brothers business and the geeza in the pictures is the web site designer.Plus he is the wrong colour to be me :lol:

I am actually a snowboard instructor so refrain from abusing skiers,at least in public :eyebrows: