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Fuse for 300Va transformer and 6amp capable filter
Fuse for 300Va transformer and 6amp capable filter
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Old 3rd November 2019, 01:58 AM   #11
KevinHeem is offline KevinHeem  United States
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Fuse for 300Va transformer and 6amp capable filter
Quote:
Originally Posted by DF96 View Post
24V secondary will give you over 30V DC; not sure if this is what you want.
I agree...30V is too much for an ACA
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Old 3rd November 2019, 01:19 AM   #12
Steve Luck is online now Steve Luck  New Zealand
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See PDF attached for power supply I've bought and MFR requirements for transformer:

ULN-PS7-E.pdf

and it's been modified for 24volt DC output not 25 so should be good to go.

Last edited by Steve Luck; 3rd November 2019 at 01:24 AM.
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Old 3rd November 2019, 01:33 AM   #13
KevinHeem is offline KevinHeem  United States
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Fuse for 300Va transformer and 6amp capable filter
I see, it's a regulated power supply which drops ~5V. Have others been successful with this type of supply?
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Old 3rd November 2019, 01:53 AM   #14
Steve Luck is online now Steve Luck  New Zealand
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Quote:
Originally Posted by KevinHeem View Post
I see, it's a regulated power supply which drops ~5V. Have others been successful with this type of supply?
Yep see here:

ACA amp with premium parts

I'm building two seperate supplies one for each ACA and putting them in the same chassis as the ACA with a big hole in the top for the Toroidy to show through. Toroid base plate and internal space in the chassis both 150mm so I might need to open the holes on the ACA chassis brackets by the tiniest fraction each side to get it all to fit!!! Not sure yet if i'll be able to bolt the supply transistors direct to the chassis base plate or if i'll need slightly thicker strips of Aluminium to act as a heat pipe to the sides - I can get hold of 3mm x 25mm strips at local DIY store.
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Old 3rd November 2019, 03:09 AM   #15
trobbins is offline trobbins  Australia
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The switch in your combo IEC/fuse/switch is likely to be the weak link with time. It has a 6A 250VAC rating (if it is a KC01-104), but I'll bet my bottom dollar that is for AC1 resistive load switching (which is the kindest AC load to switch). Given its a toroidal power transformer, the in-rush primary current is highly likely to be more than 10x the VA rating, and possibly up to 20x for the first peak. That puts the first current peak at least above 10A and possibly upwards of 20A.

You are probably using a substantial rectifier and capacitor filtering, which although it may not increase the initial inrush peak, may well extenuate the inrush duration.

That's not to say the switch would fail soon, but just saying you may get switch contact issues sooner rather than later.
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Old 3rd November 2019, 03:51 AM   #16
Steve Luck is online now Steve Luck  New Zealand
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IEC Switch is 10amp:

IEC Fuse Chassis Male Power Plug with Switch | Jaycar Electronics New Zealand

Fingers crossed this all comes together. I'm planning to bolt the power supply to the top of ACA on standoffs for some ventilation as long as it doesn't cause problems. Then the base of the ACA needs bolting to the shelf it sits on. We've not had a shake bigger than a 3 for a while in Wellington but thankfully our house is on solid conc foundation not wobbly poles!

IMG_0522.jpg
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Old 3rd November 2019, 04:05 AM   #17
trobbins is offline trobbins  Australia
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Steve, you can typically push out the switch insert and check the rating. My combo units have a 10A rating, but on inspection that was just for the IEC and fuse parts.
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Old 3rd November 2019, 05:08 AM   #18
Steve Luck is online now Steve Luck  New Zealand
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Great tip :-)

Solves the problem of how to make handed power supplies with the switches the same way up!

But yep that's a bugger the Switch says 10amp 125v and 6(2) amp at 250v not sure what what the bracket with the 2 is for. May have to find a better switch after a while then - at least I know now that it can be swapped out.

Cheers for that. Getting some nice warm weather from Oz at the moment. Enjoy the rest of your weekend and thanks.
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Old 3rd November 2019, 06:54 AM   #19
rabbitz is offline rabbitz  Australia
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Check with your transformer manufacturer for fuse rating. Altronics 300VA suggests 5A SB and others brands vary. ESP P3A suggests a 3A SB for the primary.
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