Question: Building a Bi-Polar AC adapter

Nov 06, 2004 2 Replies

I'm about to build a bi polar power supply to power some electronic effects for electric guitar that I've built that I'm sick of putting two 9v batteries in. The basic schematic and design is the one in the Craig Anderton books. So, here's my first dumb question:



  1. The power transformer should be mounted right on the chassis, right? That's what I've seen in every other piece of equipment I've poked my nose in, but I figured I'd get a second opinion here.
  2. The voltage regulators I got from mouser (according to their tech) require no heat sinks, as they're insulated with something. Is it a bad idea to use these in a project that might be turned on for several hours at a time? Should I get the "old" style regulators and use sinks instead of these insulated ones? My concern is that while the regulators may not be a danger to nearby capacitors, will they be prone to shut down more quickly than the ones that require sinks? I'm not going to put any caps too close to them anyway, but if anyone out there has built this before mabye you could share your troubleshooting experience with a less experienced builder. Thanks in advance, Jason Myers

Well, (for protection) I figured on using a heavy gauge wire for the ground line and the supply lines, as well as building it in a heavy-duty aluminum chassis, and, of course, one and only one common ground point. Using heat shrink tubing on any exposed wire, especially from the AC cable seems like a good idea. Also mabye running out of the house fast as I can when I first turn it on, and carefully re-entering if there's no smoke coming out. Seriously, though, mabye I'll remove the insulator with a wire brush and drill a hole in each one of the regulators and attach a sink to it. Have you used these (new or old) regulators for anything? Do they really heat up that much? Personally I haven't, so I'm curious about that. Thanks for the tip! Jason

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