Amp PS question

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I wired up the power input, fuse, and 2P switch for my amp. Checked the leads and the 40-0-40 secondary shows 42-0-42 V AC RMS. The transformer also has a 12-0-12 secondary, which reads 13.2-0-13.2. I think this means I've properly hooked up the 115V primary to the mains input. All secondaries and 230V primary are disconnected.

When I hook up the two 40V secondary outputs to the rectifier bridge ~ side with nothing on the +/- side of the rectifier bridge, and the 0 disconnected, after flipping the power switch I get a brief hum and the fuse blows.

Is this normal? Or is my bridge defective? It's rated 400V 25A. Not sure I understand how this could happen with a functional rectifier bridge. Or is it because it's not closing with the 0? I'm careful to make sure nothing is shorting - connections up to the rectifier bridge use insulated spade quick connects, apart from the 0 which will be soldered. I have that loose end safely held by a crocodile clip.

I'd like to sort this step out BEFORE hooking up the reservoir capacitors and 0...
 
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Never mind - found the problem. With a magnifying glass I could tell the somewhat poor print on the bridge said +/~, not +/-. Problem solved. It had a bit of the print lost in the ~ making it look like - at first glance.
 
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