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Old Jan 18, 2011, 10:48 PM
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USA, AK, Houston
Joined Aug 2005
790 Posts
You don't need a fusable link on the dc side since the only thing that can short is the negative to the positive post which causes the power supply to shutdown due to it's internal fault protection.

Basically, to make the power supplies work in series you need to float the DC side or AC side from ground. Most people float the AC side because it's simple to remove the ground pin from one of the cords then isolate the units, but I thought it better to float the DC side because I didn't like having the AC side floating, didn't want to deal with case isolation, and because it's a lot more convenient to carry around when it's not installed in a box or case or something.

In my case I only floated the dc gound on one power supply and made sure that it was the one that provides the positive for 24vdc. This means that the entire unit is grounded to dc- for 12v off of the first power supply and 24v off of both.

I am thinking about building two more of these for sale to other modelers but they are expensive to build because I use quality AMP connectors (with the nice crimper), good quality binding posts, and Y power cables. Also, the time to modify these is extensive because I have to remove the existing breakout board, jumper the pins to make it turn on, add a resistor to the fan, fabricate the front cover (this time I'll make it one piece so that it mechanically joins the power supplies together), install the binding posts, wire up the binding posts to the studs on the inside, then make the two front mounting posts out of plastic.

Cost of materials and a little labor to put it together would put these at $100 each and that wouldn't include shipping.

On the flip side, it's a really nice package and works very well. If anyone is interested in having me build one of these PM me. I'm not wanting to get in the business or nothing, but I was thinking about building myself a second unit and it wouldn't really be that much more work to toss together a few more while I'm at it.

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