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  #1 (permalink)  
Old 14th February 2013 , 09:14 PM
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Default soundcraft mixer died...

I heard a couple of pops, not even loud, and the audio was still going, until suddenly only white noise. No power light on the mixer anymore.

It is a small soundcraft compact 10 (http://www.soundcraft.com/products/product.aspx?pid=121 ), a discontinued model.

I checked the power supply with a voltage meter... seems to be good. Tried another power supply, just to be sure.. still dead. The mixer does smell a bit.. not very nice. Not really a burning smell and not very strong either, but clearly not good.

Opened up the mixer, but I can't get to anything without literally removing every cap of every pot that's on the board (and the caps seemed to be glued to the pots), so that I can then get lift the front off of the PCB. So I don't even know if there's replaceable fuse in there.

Anyway, does this sound like anything you can give me advice on?

(I so very much need this mixer to work.. ordering something new will probably leave me unable to do any audio/video work for at least, say, two weeks... I live on a small tropical island, have to order everything from the States and have it flown in).
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Old 16th February 2013 , 05:36 PM
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It sounds to me like a power supply issue. Unfortunately the mixer has to be stripped to find the fault. Not recomended if you are not experienced in these matters.
I can repair it for you but looks like it will be more convenient for you to purchase a replacement.
www.jonsnell.co.uk
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Old 18th February 2013 , 01:21 AM
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Quote:
Originally Posted by Harleyjon View Post
It sounds to me like a power supply issue. Unfortunately the mixer has to be stripped to find the fault. Not recomended if you are not experienced in these matters.
I can repair it for you but looks like it will be more convenient for you to purchase a replacement.
www.jonsnell.co.uk
Regards
Hi Jon,

thanks for you reply. Unfortunately, I cannot send it to you to repair it, I'm in the Caribbean, it would just be too expensive in shipping costs.

I was able to open up the mixer afterall. Seems that the transistor is not good anymore. (A little brown on the backside of the PCB where on the other side the transistor is situated). It is one similar to this one: http://www.ebay.co.uk/itm/390188925699 yet with another number next to the logo. Instead of 3735 there's 30G350 on mine.. don't know what kind of difference that makes.

Would you happened to know that?

Also, the capacitor next to it is a bit round on the head, instead of flat like others on the board. No leaking as far as I can see, though. But I'm not sure, as there's lots of corrosion on the inside of metal cover of the mixer situated where the transistor is. This is the info written on the black and grey capacitor:
Jamicon
352CO
1000?F 25V
WG 105?C

Maybe replacing those two things can get the mixer working again? (But what made the transistor die in the first place?).
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Old 18th February 2013 , 01:33 AM
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some images:







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Old 18th February 2013 , 02:34 AM
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It is an International Rectifier IRF540... specifically it is a MOSFET voltage rectifier - http://www.irf.com/product-info/data...ata/irf540.pdf

The bulging top of the electrolytic capacitor is a sure sign of damage and that should be replaced also. From your description it sounds like it's a 1000uF 50V electrolytic.... any 1000uF electrolytic rated 50V or above that will fit in its place can be used as a replacement (be sure to note the correct orientation when replacing it).

The cause could have been a mains spike or a faulty external power supply (have you tested the power supply?)

Most large US mainland electronics suppliers (like Farnell or Mouser) should carry them, but I don't know about any suppliers based in the Caribbean... at least you can check any you know of with the correct part numbers and values to quote.

BTW, I use the exact same mixer for sub-mixing my keyboards in my live rig
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Old 18th February 2013 , 03:40 AM
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Hello Dave, thanks a lot for your input!

Quote:
Originally Posted by Dave Boulden View Post
It is an International Rectifier IRF540... specifically it is a MOSFET voltage rectifier - http://www.irf.com/product-info/data...ata/irf540.pdf
I know not that much about electronics, so just to be sure: To replace the faulty transistor, I just need to ask/look for an(y) International Rectifier IRF540, and I would get the one I need? I don't have to worry about the brand or the code '30G350' that is on the original?

Quote:
Originally Posted by Dave Boulden View Post
The bulging top of the electrolytic capacitor is a sure sign of damage and that should be replaced also. From your description it sounds like it's a 1000uF 50V electrolytic.... any 1000uF electrolytic rated 50V or above that will fit in its place can be used as a replacement (be sure to note the correct orientation when replacing it
No, it's an 1000uF 25V capacitor. So, that would mean any 1000uF electrolytic rated 25V or above is the one I need, right?

For example this one here? http://www.kpcomponents.ca/product_i...roducts_id=998

On the example above I cannot find the code '352CO', though. And I don't know if that makes any difference (I have no idea what it stands for). Also, in front of the 105 degrees Celsius, on my faulty capacitor is written 'WG' whereas on the example above there's written 'TK 105 degrees Celsius'. I do not know if that is something to take into account because also in this case, I have no idea what it stands for.

How can I see what the correct orientation is, when replacing it?

Quote:
Originally Posted by Dave Boulden View Post
The cause could have been a mains spike or a faulty external power supply (have you tested the power supply?)
By a mains spike you mean a spike in the electricity network in the house? Shouldn't the external power supply have been able to handle a bit of spiking? (It can't have been that much.. I'm on an off the grid solar system..the output of the converter should be pretty stable. Also, I have an extra voltage regulator between the wall socket and my mixer, computer, monitors etc. that compensates for too low or too high voltages. I can actually hear it clicking when it's doing that).

I did check the plug of the external psu with a voltage meter. It gave me: 19.7 VDC. A bit much, seeing as on the power supply it is written that the output should be 12 V.

Quote:
Originally Posted by Dave Boulden View Post
Most large US mainland electronics suppliers (like Farnell or Mouser) should carry them, but I don't know about any suppliers based in the Caribbean... at least you can check any you know of with the correct part numbers and values to quote.

BTW, I use the exact same mixer for sub-mixing my keyboards in my live rig
Yeah, I like it a lot. Simple to set up in combination with a computer, easy to work with and not very space consuming. It would be a waste if I had to throw it away when it's maybe only replacing the capacitor and rectifier that will get it to work again.

(Except that the external PSU seems a bit off as well... Do you have any advice on how to further check that? Or, what is your 'verdict' on the PSU given the info I wrote about the voltage level just now, earlier?).

Thanks again!
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Old 18th February 2013 , 11:00 AM
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Quote:
Originally Posted by Turtuga Blanku View Post
No, it's an 1000uF 25V capacitor. So, that would mean any 1000uF electrolytic rated 25V or above is the one I need, right?

For example this one here? http://www.kpcomponents.ca/product_i...roducts_id=998
Sorry, mis-read your post, yes 25V or above. The one in the link is quite suitable. You only need to look for an electrolytic that is 1000uF and 25V (or higher) in th replacement... the other markings don't have to match. There will be a vertical stripe down one side of the capacitor's body that marks the negative lead, you simply need to put the replacement in the same way round with the negative lead in the same of the two PCB holes.

The brand of the voltage rectifier is "International Rectifier" and it is their logo (which has an "I" and an "R" in it) also marked on the body. "IRF540" is the model number of the component. You should ask for an "International Rectifier IRF540 or direct pin-compatible equivalent". If offered an IRF540a, IRF540n then that is essentially a suitable compatible alternative version of the same thing. The parts supplier should have details of which parts are compatible replacements if they don't have the exact part.

Quote:
Originally Posted by Turtuga Blanku View Post
By a mains spike you mean a spike in the electricity network in the house? Shouldn't the external power supply have been able to handle a bit of spiking? (It can't have been that much.. I'm on an off the grid solar system..the output of the converter should be pretty stable. Also, I have an extra voltage regulator between the wall socket and my mixer, computer, monitors etc. that compensates for too low or too high voltages. I can actually hear it clicking when it's doing that).

I did check the plug of the external psu with a voltage meter. It gave me: 19.7 VDC. A bit much, seeing as on the power supply it is written that the output should be 12 V.
That is what I meant, but probably that will not be the case in your situation. The high voltage on the PSU when not plugged into the equipment is not unexpected... it is probably an unregulated PSU... and so that is why one of the 1st components to receive the PSU's power is the voltage rectifier that has blown. The PSU is probably OK.

Good luck!
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Last edited by Dave Boulden; 18th February 2013 at 12:57 PM. . Reason: corrected my rubbish typing! <
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Old 18th February 2013 , 12:51 PM
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Hello Dave,

Thanks a lot for the extra information. It is very helpful. Much appreciated.
I'll let you know how this has all worked out. (Hopefully, I can get the parts here quickly).

Cheers!
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Old 19th February 2013 , 11:04 PM
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I would say that replacing the capacitor with a 1000uF 25volt 105Deg will probably cure your problem as the IRF540, being a MosFet will self protect and just shut down.
Hope that helps.
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Old 22nd February 2013 , 12:42 PM
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Quote:
Originally Posted by Harleyjon View Post
I would say that replacing the capacitor with a 1000uF 25volt 105Deg will probably cure your problem as the IRF540, being a MosFet will self protect and just shut down.
Hope that helps.
Cheers, Jon!

B.t.w. I took off the capacitor by rocking it side to side a bit (as per advice someone had given me. One lead came loose, the other one broke. PCB still alright) and got a better view of the information written on it. It is a 100uF 25V 105Deg capacitor (instead of 1000).

I'll have to order a new one through the internet as I can't get one on the small island that I live. I might order a new IRF as well, just to be sure, since it'll take some time before stuff gets here, from the US, should I need it after all.
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Old 23rd February 2013 , 12:26 AM
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I tried to find the correct International Rectifier IRF540 over here: http://www.digikey.com/scripts/DkSea...=0&y=0&cur=USD

And found out that there are 33A and 36A versions. And there are a couple of more differences.. whereas all the info I have on the IRF is what is written on the IRF itself:
30G350 (probably a code used for batch tracking)
Morocco
IRF540

Hmmm... And I cannot find the schematics of this mixer...
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Old 3rd April 2013 , 01:18 AM
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It has been a while, because only this past weekend did I get the parts that I needed. Last night, someone helped me out with the soldering. First the capacitor was replaced. Still dead. Then the transistor. And then it worked again! I am very content.

Thank you all for your interest and for helping me out by giving information and advice. Appreciated!

Cheers.
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Old 3rd April 2013 , 01:31 AM
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Glad to hear you've managed to successfully repair your mixer. Well done!
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Old 15th June 2013 , 02:08 AM
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What an AWESOME thread to find.

Woke up this morning to find my Compact 10 in the EXACT same condition. Took it all apart, and found the same capacitor and MOSFET burnt up.

Only question for me now is up a few posts, it was asked 33A or 36A for the IRF540. Anyone have more insight? Does it matter?


Edit:

Now that I look at mine more clearly, it looks like I do NOT have the IRF540 in my Compact 10 at all!
Looks to be a STP24NF10 .... anyone know if those are swappable? Which would you experts suggest?



Thanks,
Mark
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Old 19th June 2013 , 06:11 PM
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Hi Mark,

Sorry to hear about your problem..luckily it's easy to fix, if indeed it is the same as the problem I had with the mixer!

33A or 36A for the IRF540? I looked in the info I've gotten and gathered when having this problem and was made to understand that it does not really seem to matter which one you choose.

However, since you do not have the IRF540 after all, I would probably just look for a replacement STP24NF10, e.g.:
http://www.digikey.com/scripts/DkSea...ords=STP24NF10

Let me know how things are working out for you!
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