I'm trying to build this simple regulated power supply, and

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Technical and speculative discussion of amps, cables and other topics.

the fuse keeps blowing immediately when the power is switched. The PS consists of:
The basic circuit can be found at many web sites, so it is not a design issue. In general component sequence is:
switch
0.312A fuse
parallel pri/sec 117/17V@0.68A
1N4003 diodes
470 uF ripple filter caps
LM7812 regulators
The transformer itself blows the fuse with nothing connected.
Transormer primaries are each 60 Ohm, secondaries are each 5 Ohm, there are no shorts between turns or with core. All passive elements test normal/consistent with an analog VOM when out of the circuit.
I'm no circuit expert, I would just like to know what basic priciple of circut function I am missing here that causes the fuse to blow.
Dumb question of the day: Why don't wall wort transformers fail when they are plugged into the wall?
Thank you for your time.

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Topic - I'm trying to build this simple regulated power supply, and - NewbieBaby 17:57:22 03/15/05 (6)

Parallel Secondaries? Must be correct phase! - clifff 01:54:09 03/16/05 (5)

Re: Parallel Secondaries? Must be correct phase! - NewbieBaby 05:16:02 03/16/05 (4)

Oh I C - clifff 05:43:01 03/16/05 (3)

The notion of phase provokes thought. - NewbieBaby 06:01:52 03/16/05 (2)

They MUST be connected so that ... - clifff 06:59:55 03/16/05 (1)

PS: Thanks a Whole Lot n/t - NewbieBaby 18:03:51 04/04/05 (0)

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