He is right.
A close rated fuse will not allow a transformer to start reliably.
You must use a soft start. For 300VA use 40r of Power resistors and a 200ms delay on the bypass, or two CL60 and a 500ms delay on the bypass.
I know 300VA is on the limit for needing a soft start circuit but I was advised that as long as I didn't exceed that I wouldn't need to bother with soft start circuits etc.
Nice, neat looking board that peranders, pity the case I have is too small for even it though, I will keep it in mind for any future PSU builds I make.
Think i'll get the thing working first then I might well look into trying to squeeze a soft start circuit in somehow, maybe as you say a couple of CL60's, i'm not so keen on using resistors.
Nice, neat looking board that peranders, pity the case I have is too small for even it though, I will keep it in mind for any future PSU builds I make.
Think i'll get the thing working first then I might well look into trying to squeeze a soft start circuit in somehow, maybe as you say a couple of CL60's, i'm not so keen on using resistors.
Soft Start is really personal choice at 300VA. It's a good idea as everyone is saying, you can get away with the smaller Mains Fuse which will offer better protection.
My amp uses 2 x 500VA transformers. The PSU is so huge that I just couldn't fit in a Soft Start, so, after VERY CAREFUL testing I run it without. It doesn't trip any house breakers, nor does it rupture its mains fuse. However, the two transformers do share a 10A TL fuse.
Before anyone comments, the bolts through the inductors forming the CLCC filters are aluminium.
My amp uses 2 x 500VA transformers. The PSU is so huge that I just couldn't fit in a Soft Start, so, after VERY CAREFUL testing I run it without. It doesn't trip any house breakers, nor does it rupture its mains fuse. However, the two transformers do share a 10A TL fuse.
Before anyone comments, the bolts through the inductors forming the CLCC filters are aluminium.
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That's quite a build you have there, very impressive, is that stacked toroidal's I see?
Just been raking through a box of components and found a thermistor, a P250L left over from a valve amp I built years ago. Not sure it will do for a current limiter in this case but might be worth looking into.
Just been raking through a box of components and found a thermistor, a P250L left over from a valve amp I built years ago. Not sure it will do for a current limiter in this case but might be worth looking into.
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Just doing that right now, it was one of a pair I got for a 25W EL84 amp, they were soldered across the mains socket tags, memory fails me as to the power consumption but the transformer was smaller, probably around 180VA. I think it was a basic power spike suppressor circuit but probably not suitable in this case.
I've just moved house so I can't find the actual Thermistors that Dad bought, but never used, but here is a starting point.
Buy Thermistors Thermistor NTC 5 Ohm 20% Radial Epcos B57213P509M301 online from RS for next day delivery.
Buy Thermistors Thermistor NTC 5 Ohm 20% Radial Epcos B57213P509M301 online from RS for next day delivery.
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