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biggsd  
#1 Posted : Saturday, January 4, 2014 9:58:41 AM(UTC)
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Hello,

I have completed my dual stereo DAC. which has 2 x Placid BP supplies with oversized transformers and an LPBS.

Unfortunately I am regularly blowing the 2 x 2a fuses, and it appears to happen when the DAC is turned off along with a whole lot of other stuff. Intermittently. Back on - doesn't strt until i replace the fuses.

What is the best fuse rating for a standard Dual mono Buffalo DAC, and is 2 x 2a (4a) enough? It was fine with just one supply in it, but now I have added the second do i need to up the fuse ratings?

Any help would be great :-)

-Dave
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avr300  
#2 Posted : Saturday, January 4, 2014 12:21:17 PM(UTC)
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It all depends of the tranformers beeing used. You said oversized, pls. specify.
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LeonvB  
#3 Posted : Saturday, January 4, 2014 6:55:11 PM(UTC)
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Originally Posted by: biggsd Go to Quoted Post
Hello,

I have completed my dual stereo DAC. which has 2 x Placid BP supplies with oversized transformers and an LPBS.

Unfortunately I am regularly blowing the 2 x 2a fuses, and it appears to happen when the DAC is turned off along with a whole lot of other stuff. Intermittently. Back on - doesn't strt until i replace the fuses.

What is the best fuse rating for a standard Dual mono Buffalo DAC, and is 2 x 2a (4a) enough? It was fine with just one supply in it, but now I have added the second do i need to up the fuse ratings?

Any help would be great :-)

-Dave

I agree with AVR. The fuses required will depend on what you're putting in the chassis. I'm using 4 30VA R-cores, which is already plenty of overkill, and have never blown one of the 2A fuses. Are you sure it's not getting blown at startup?
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biggsd  
#4 Posted : Saturday, January 4, 2014 8:58:04 PM(UTC)
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Hello

So, in the chassis is 2 x 160w transformers (yes 160w) for the Placids, and one small standard one for the LCDPS (for the Digital parts).

These are much larger transformers, but make a massive difference to the bottom end.

RS Part number (RS site is currently down) 671-9012

Thanks!
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LeonvB  
#5 Posted : Saturday, January 4, 2014 10:26:26 PM(UTC)
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With 2x 160VA plus 1x15VA, I'm surprised you don't blow the fuses all of the time. The inrush current of a transformer is usually 2-5x the rated load current. In your case, the inrush current could be as high as 335VA x 5 / 230V = 7.3A.

So if you upgrade your transformers to that of an amplifier, you also need to beef up your fuses. As a note, if you are using 2 fuses in most cases both poles (L+N) are protected. This does not mean you can put 2+2 together. I suggest reading the datasheet of the IEC/fuseholder you are using for the exact configuration.

Please also check if ALL of the parts you are using (IEC, wiring, etc) can handle the increased current.
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biggsd  
#6 Posted : Saturday, January 4, 2014 11:34:00 PM(UTC)
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After the last blow I put in 2 x 3A into the fuse holder. Now I know this I will go get some bigger ones. Yes I see what you mean, one fuse for each pole.] (one for L and one for N). So, I currently have a 3a when I need like an 8? I will try a 4 and see how we go. It only seems to happen when it is turned on along with lots of other stuff. If I just turn the DAC on last it seems to be fine.

All wires and connectors are decent, so I will go through and check everything.

Sounds really great with the beefy transformers though.....



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avr300  
#7 Posted : Sunday, January 5, 2014 3:32:58 PM(UTC)
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Also pay attention to the fuse specification, especially the speed.

Take a look here:


http://www.littelfuse.com/technical-resources/faqs/~/media/Files/Littelfuse/Technical%20Resources/Documents/Reference%20Documents/Littelfuse_5x20mm-IEC-Fuse-Cap-Marking_guide.pdf


For reference, I use a T630mA (@230v mains) for my 160VA toroid (for my Placid). No problem at all, I never blew that.

You don't want a fuse to big. If you get an error in the circuit you have to ensure that it's the fuse that breaks.

Edited by user Monday, January 6, 2014 6:59:36 PM(UTC)  | Reason: Not specified
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