carlosfm said:Mmmmm...
Are those caps for the PSU or are you putting 2*4,700uf caps near each chip?
Anyway, seam a little too much...
Watch out for that mains power switch...
this was (is?) for the psu.. I was going to put 2200uF near each chip on each rail.... 4 chips total.. is this alright?
mains switch?
SkinnyBoy said:
this was (is?) for the psu.. I was going to put 2200uF near each chip on each rail.... 4 chips total.. is this alright?
mains switch?
Nuclear power!
lol.
Yes, the mains switch to power on your amp.
It will suffer.
Large inrush current with all that capacitance.
You have to get a big one, or... bang!
lol.
carlosfm said:
Nuclear power!
lol.
Yes, the mains switch to power on your amp.
It will suffer.
Large inrush current with all that capacitance.
You have to get a big one, or... bang!
lol.
really?
really?
really?
you sure??
SkinnyBoy said:
really?
really?
really?
you sure??
Yes, lol.
Try it.
I use to put a 10 ohm / 5 w resistor in series with one of the primary wires, coming from the mains switch.
That solves a lot of problems, no more blowed up fuses at power on.
carlosfm said:It's more than enough to use one single fuse on one of the primary wires.
Not on the secondaries.
every schematic I have looked at has a fuse on each rail... plus I have 4 chips... if one goes short circuit... something is going to burn cos theres no way the main fuse will blow...
SkinnyBoy said:
every schematic I have looked at has a fuse on each rail... plus I have 4 chips... if one goes short circuit... something is going to burn cos theres no way the main fuse will blow...
Don't worry, the main fuse WILL blow.
The main fuse can be around 4 amps in your case.
Much smaller than if you put fuses on the secondaries.
And, when there's a problem, the primaries blow, the secondaries won't.
Because the primaries' wire are much thiner than those on the secondaries.
If you have a burned transformer, it's the primary.
If you put one fuse on the primary, you are protecting it all.
carlosfm said:
Don't worry, the main fuse WILL blow.
The main fuse can be around 4 amps in your case.
Much smaller than if you put fuses on the secondaries.
And, when there's a problem, the primaries blow, the secondaries won't.
Because the primaries' wire are much thiner than those on the secondaries.
If you have a burned transformer, it's the primary.
If you put one fuse on the primary, you are protecting it all.
4 amp fuse won't handle the inrush current of three 250VA transformers... if I have seperate fuses for each amp module, if theres something wrong with the chip or whatever, these will blow... even a 4 amp slow blow fuse probably wouldn't cut it.. I was thinking 8 amps... allow the transformers to give twice their rated power... but if there is a problem it should blow.... hmm..
SkinnyBoy said:
4 amp fuse won't handle the inrush current of three 250VA transformers... if I have seperate fuses for each amp module, if theres something wrong with the chip or whatever, these will blow... even a 4 amp slow blow fuse probably wouldn't cut it.. I was thinking 8 amps... allow the transformers to give twice their rated power... but if there is a problem it should blow.... hmm..
Wait a minute...
Is the mains voltage in Australia 110v?
If it is, you're right.
If it's 220~240v, I'm right.
And I use a 10 ohm resistor inline with one of the primary wires (the one that has the fuse).
I ah.. don't think mains voltage has anything to do with the inrush current required by toroidal transformers... (well, it does, but its still there) 4 amps is only 960watts..... not enough.... especially considering the inrush current.. the fuse is only there incase of failure... failure which will result in quite a low resistance, and quite abit of current flowing.... with just a fuse on the mains, I could have a near short (near enough) that would cause 960watts to flow through the circuit.... thats 125% of the transformers rated output.... it would fry, and the fuse would do nothing.... there needs to be some fusing on the secondary....
carlosfm said:
And I use a 10 ohm resistor inline with one of the primary wires (the one that has the fuse).
wait.. huh? a resistor inline with the mains??? you have to switch it out after a second or 2 though...
carlosfm said:Man, if you need a 4A fuse for 220v mains, for 110 you'll need 8A.
Why disconnect the resistor?
The powersupply will be not as stiff with the resistor (mind you you have a lot of capacitance, so you may not realy notice anithing)
I have a 384VA toroid on my main GC.
Without the resistor, even a 4A fuse blowed up sometimes at
switch on.
And that was with only 1000uf caps.
If I put a bigger fuse on the primary, the amp could burn and the fuse would be intact.
Now I have a 2.5 fuse and no problems.
This is for toroids, they have much bigger inrush currents at power on than frame transformers.
Without the resistor, even a 4A fuse blowed up sometimes at
switch on.
And that was with only 1000uf caps.
If I put a bigger fuse on the primary, the amp could burn and the fuse would be intact.
Now I have a 2.5 fuse and no problems.
This is for toroids, they have much bigger inrush currents at power on than frame transformers.
carlosfm said:I have a 384VA toroid on my main GC.
Without the resistor, even a 4A fuse blowed up sometimes at
switch on.
And that was with only 1000uf caps.
If I put a bigger fuse on the primary, the amp could burn and the fuse would be intact.
Now I have a 2.5 fuse and no problems.
This is for toroids, they have much bigger inrush currents at power on than frame transformers.
Did you use a slow-blow or fast-blow fuses?
GregGC said:
Did you use a slow-blow or fast-blow fuses?
Always slow.
At power-on with a big toroid you can hear a little "bonc" noise (and vibration) and then it stays quiet.
This is for a period of around 1 second.
Enough to blow a slow-blow fuse from time to time.
A resitor cures this.
No noise at switch-on, no vibration, no blown fuse and you can use the right fuse you need (you don't have to put a big fuse just because of the switch-on).
I feel more protection this way.
caps across the power switch will also help. A high-voltage (1 KV) film or paper cap across the resistor should ensure the supply is not terribly loose and the inrush current will be limited. I have not personally tried the resistor, but it helps to absorb the bump from switch-on, again from frame transformer experience (no toroids in India, at least not in single units) to have a small 10 nF cap across the switch...
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