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I put 14A diodes in a 3A power supply that came with a 5A
slow blow fuse from the factory. How high can I now go and still protect from fire? Don't care about protecting the PS. It's only being used for a dac, like half an amp. Thanks, Tweaker
Follow Ups:
I'm more intrigued by your premise that higher rated fuses somehow sound better. Do I understand that aspect of what you've said correctly? If yes, can you elaborate on that a bit? Anecdotal observations are okay as part of any explanation. Don't know if I've heard that assertion before and would like to better understand you.
Thanks
Soudek , Not much to elaborate on. Higher rated fuses sound better. Thicker wire inside. Different fuses of the same value sound different. This of course cannot be recommended as a general principal. In some well thought out cases a larger fuse may be a reasonable thing to do. As an example I'm pretty sure my amp came with a 2 amp fuse. I asked the designer what the max current the amp would draw if it was pushed to it's max and he said 3.75a. He also said it's ok to go to 3.75 fuse after putting in a 2 amp fuse. I asked him if I could go a little higher than 3.75 and he no. Of course this is just my humble opinion and your mileage may vary. Like everyone says, you gotta be safe. Tweaker
If you DIG IN to the factory specifications, you'll find RESISTANCE listed.
Too much is never enough
Thanks for the explanation. Having read it, I'm not sure why it didn't occur to me when I saw your OP that I've kind of done the same thing with my Acoustat amps. Well, I didn't do it, the gent that rebuilt them did it, but he replaced the fuses and power switch with magnetic hydraulic circuit breakers. More beef in the connection. Big improvement in sound. So yeah, I think I get it. Sometimes I can be a little slooooow.
In that particular case, the 3.75A fuse would have to be a fast-blo type. But fast-blo types use thinner wires than slo-blow. So, in the end you might be "better off" sound-wise with a 2A or maybe 2.5A slo-blow.
The 2A fuse was a fast blow.
The fuse was chosen by the designer to protect the device based on some element of the design which would be stressed by input currents larger than the fuse rating.
Whether the diodes you changed out happened to be that particular weak link in the original design that set the fuse size/rating would require intimate knowledge of all aspects of the design.
To jump to conclusions about the rest of the design based on changing out some diodes sounds very very risky to me.
I advise caution here. Based on what I know now I would recommend not increasing the value of the fuse
Ok, good response(s). The weak link thing is a proper way of looking at this situation. I'll be safe. Thanks, Tweaker
The output of the ps will dictate the max incoming AC. You didnt change the power supply design and output right? You didnt say which diodes you changed so I will assume you changed the diodes in the bridge. Their current rating is their max handing capacity so the current through them wont change, you could have measured it before and after. I think you said they already were changed.You dont need to change the fuse value.
ET
Edits: 04/25/16
It's not a question of need. I want to put the highest rated fuse in the PS that is likely to protect against any fault that could cause fire. This is for sonic reasons. Tweaker
I would dead short the output and check the current drain (quickly) and go just under that. Try sand filled fuses if you can find them.
ET
There is this neat thing out these days, it's called a search engine. Most prefer Google, you can determine one to your liking.
So why should anyone ever come here at all?
The neat thing about AA is that many folks actually try to be and are helpful, but I realize I can't win em all. Now and then someone even actually benefits from one of my suggestions. Imagine that! Didn't get my answer from your reference UM. Tweaker
Edits: 04/24/16
All we are told is that this is a DAC. Correct? And the original fuse is 5A. Yes?
Is it a slow-blow or fast-blow type? Why would anyone go out on a limb to say you can use a higher rated fuse than recommended, when doing so could be dangerous? Are you going to take the word of someone here and turn it into your own "suggestion"? Some of these aftermarket boutique fuses are not even UL-rated; that's bad enough. To then increase the current rating ad lib is rather foolish. To recommend it is even more foolish.
Why not just bypass the fuse entirely, if you're feeling lucky? (I definitely don't recommend it, by the way.)
Well Lew, I see your point about someone going out on a limb. On the other side there are electronics trained people here. I think the 2N3055 output is 15A. I'd have to check to be sure. It is not unreasonable to think there might be some more wiggle room with diodes almost 5 times the rating of the originals. It's a slow blow. Just thought I'd ask. If I was to not use a fuse at all I wouldn't have put this out. The purpose of the question was to not be reckless. I'm well aware of the no fuse at all option. Tweaker
Just because a device in the circuit is capable of 15A means pretty much nothing. You have to look at everytning in the circuit. For instance the power transformer may only be rated to handle 5A. If a winding especially the primary goes wrong you want that fuse blowing ASAP. This is a risk not worth taking.
I connected a power cord on an NAD amp and later an upgraded linear ps for my Squeezebox diectly to the power transformer primary. No switch, no fuse. That made a big difference. In both cases the power cords were plugged into something with a fused AC out for protection- one a power conditioner the other a regenerator.
ET
Edits: 04/26/16 04/26/16
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