pedal power supply question about RG's article

[mikepukmel]

Fr good reasons, more and more pedals include a protection diode in the power path to prevent folks using wallwarts with the "wrong" polarity. Once upon a time, when folks might use any old AC-to-DC adapter, there was a chance they might select one with the wrong polarity (outside ground) and fry the pedal. Then manufacturers started insisting you use THEIR adapters. Eventually folks started powering pedalboards with multi-outlet power "bricks". But once folks were incorporating PNP germanium transistor pedals into their pedalboards, power-brick makers had to include reverse-polarity outputs, which meant there was still a risk of the user running a cable from the "wrong" output to the pedal if they weren't paying attention.

So, there is still good reason for pedal manufacturers to include protection against "wrong" power polarity.

There are two ways to do so. One is to have a diode to ground, so that anything above the diode's forward voltage goes to ground, leaving the pedal powered by only 500mv or so of the "wrong" voltage (not enough to fry anything). The other is to insert a diode in series with the power supply so that the circuit is never fed anything other than the "right" polarity. The caveat with that method is that it subtracts one diode's worth of voltage. So, if the diode removes a half volt, then the circuit will still get 9v if the power source is 9.6V or thereabouts. Not that the circuit will die if it's less than that. But various circuits may well be tuned/calibrated in anticipation of 9v.

Cool thanks Mark, thinking about this. So far, I only have pedals I built myself (I gave away all my 'vintage' MXR pedals to my brother a few years back) so the risk of wiring something wrong and hooking up the wrong polarity is a lot bigger I think.

[Helmholtz]

One is to have a diode to ground, so that anything above the diode's forward voltage goes to ground, leaving the pedal powered by only 500mv or so of the "wrong" voltage (not enough to fry anything).

Please do not use this option without adding a fuse. As the diode presents a short to wrong polarity, both PS and protection diode may get destroyed without a fuse.

[mikepukmel]

I''ve been scanning Ebay for weeks now, looking for a better quality regulator board. I bought a few last year, couple dollars each I think 2.00 or so, that included the board, a few caps, diodes, LED, regulator and WAAYYY too small heat sink. I bought some heat sinks from Mouser, was able to drill the board out a bit, and glue in heat sinks, something like 4 times the height and many times the mass. They still get hot but not so hot you can't touch them.

I found some boards with "Audiowind" name, seen the name a few times before. They cost more, but look a little better quality. Bigger caps, and heat sink, layout a little better (at least what I can tell).

Assembled and (at least they say) tested:
https://www.ebay.com/itm/9V-DC-Volta...igpv:rk:8:pf:0

If I bought the PCB and parts, could build for 8 bucks I think. I like to solder and fiddle with stuff, but if this board is all done, maybe just go with that. The heat sink is like 10x better than the ~2.00 boards I got last year. Have no idea about the regulator chip itself.

Still not so close on transformers. The thread started out looking for suitable transformers, but looks like not many made these days, so many discontinued (I won't comment on the newer sw***hing PS thing, seems to stir up a lot of bad blood )

What Id like to do, I think, is get say 4 or 5 of these reg boards, mount them inside a nice case with a vent screen on the back. Put a transformer for each reg, then put a switch, fuse, LED on top and dc jacks on the front. Total cost is more than, say, the Pedal Power ISO5 (that is smaller, lighter, factory built, tested etc), but, heck I can build this!!!

Are these transformers OK:
https://www.jameco.com/webapp/wcs/st...gDrillDownView

Pricey to ship, but 8 bucks is cheaper than I found elsewhere.