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Now, what I would do next is, check (and replace) the NE5517 on the filter card. LM13700 in some versions. He is the "brain" behind the prot-lim circuit. 
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gostaria de receber o esquema da rcf art 315.....Comment
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Originally posted by Enzo
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Hi, sorry for the thread ressurection.
My name is Marco, i'm from Portugal. I found this forum while googling for a solution to a problem i'm having with my RCF ART312A MKII speaker and i hope you can offer me some advise. Here's the issue:
When i turn it on it works fine for about 10-15 min then it cuts out in to protection and the LIM LED lights on. If i turn it off and on again the LIM LED stays on and i have no sound. If i have it turned off for a long period it powers up with sound againg for another 10-15 min then the problem comes up again.
One thing i noticed is that when the speaker enters in protection, if i turn the volume all the way up i can still hear some sound through the 12" driver, very low volume but it's there.
Now some backgroung about me, i'm not an electronics technician, i'm used to do all the maintenance and repairs to my band's gear but it's the normal guitar electronics repair, the odd jack/pot replacement/cleaning on an amp, etc. I'm not used and i don't have the tools for PCB micro-components replacement.
For example, if you think that my problem lies with the EQ/filter board i'll be more confortable replacing the entire board, i don't think i would be able to replace those MMBTA42s and MMBTA92s transistors (i already have an offer from RCF Italy to send me a new EQ/filter board free of charge but they say that they don't think the problem should be there, their solution is to replace the entire power amp module...).
I'm hoping i can get this fixed somehow, i don't want to spend about 300€ on a new poweramp module because i bought these speakers used and payed about 400€ for each.
I thank you in advance for all the help you can offer me on this issue. If this has been already covered on another thread i would apreciate a link for it.
Regards
MarcoComment
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Sounds like you have 2 of those speakers? Swap the power amp module into the other unit and you will know if the module is the problem.Originally posted by Enzo
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yeah, i'll get the other one home to start changing parts to see if i can narrow the problem down to one section.Comment
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At first view i have 4 diferent parts on this speakers: the PSU, the main PCB, the filter board and the drivers. I'll start by the easier ones (PSU and drivers) and work my way up to the PCB's.
Cheers
MarcoComment
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Hello Marco.
The 312 MK2 has a different amplifier module. The first generation was built with the 2 step, H-class amplifier and with the classic transformer power supply. The previous discussion was about that model.
Now, the MK II utilizes a Self Oscillating Power Supply, and a D-class amplifier. In my humble opinion, your problem may originate from component failure due to extensive vibration. Basically, you can visually inspect capacitors, resistors (especially the bigger ones) and transistors for broken leads. But I must warn you, do not engage more into the repair, than your skills allow you to. There are lethal voltages inside, even if the amp is turned off (with high voltage capacitors not being discharged). Good luck.Comment
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Hi, thank you for the adviceOriginally posted by paleeman View Post. I'm aware of those voltages and i don't mess with anything i don't know well enough.
So, form reading your post i'm now thinking that i don't need to replace the filter board. I'll get the other speaker and start changing parts to see if i can narrow the problem to a specific area.
CheersComment
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Sorry Marco. I owe you an apology. I had no intention to confuse you. As I was reading your reply, I came to the conclusion, that you probably have the older version, with the base amp board and the filter card. If that is the case, I suggest you to replace the capacitor marked C52, value 10uF/16V.
Good luck
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Hey paleeman, that's the exact model i have, a 312A MKII
I'll see if a can replace that capacitor, seems big enough to be removed with my solder iron
Can i ask you one more question? I dont have one of those capacitors at hand and the nearest electronic shop is 30km away. I do have those more common capacitors (cilinder shape, two poles) here and i think i have one with that value. Can i try one of those just to see if it solves the problem and then get a direct replacement from the store or are these diferent from the ones i have (i'm thinking about polarity issues)?
Cheers and thanks for the tip
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Yes, you can use the electrolytic capacitor, that you have just described. Polarity should be: negative lead of the the capacitor soldered to power supply reference ground.
You are welcome. Let's hope that this solves your problemLast edited by paleeman; 03-26-2014, 09:28 PM.Comment
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Sorry but i didn't understood this part. In the position of the pic you posted is the negative the lower or the upper soldering point? BTW i have fount the 10uF 16V capacitor. I'm getting the iron warmed upOriginally posted by paleeman View Post
I have som old boards that i keep from broken PSU's and printers and they have caps like this so i'll practice removing those first before atacking the RCF board.Comment
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Replaced the cap, the speaker is now running fine for 17 min, keep your fingers crossed!
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Yeah!!! 30 min without cuttig out! I think the problem is solved. I'll take it to my band's rehearsall space this weekend and give it a good workout at volume to see if it handles.
Paleeman, i can't thank you enough, you just saved me a lot of money and the headache that would come with solving this problem. If i'm ever in Hungary i'll have to find you and buy you a couple of beers. THANK YOU
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