What's inside the Dunlop DC Brick? or foldback current limit

[cd]

I'm asking from a pure curiosity/mental exervise standpoint, since I already have a Pedal Power 2, and would advise anyone who has the dough to get one, or build yourself a Spyder

Let's see: the transformer is external, since it takes a proprietary AC adapter into the brick.  The AC adapter supplies 18VDC @ 1A regulated into the Brick.  The Brick then spits out seven 9VDC taps and three 18VDC taps.  Now it's advertised that the Brick can handle up to an *average* of 55mA per 9VDC tap, or a total of 375mA - which leads me to believe there's a simple LM317 or some other regulator, with all 7 9VDC outputs in parallel, like a daisy chain.  Each output is not isolated and short circuit protected like the PP2, since it's also in the manual that the Brick can only be used with tip negative effects (stick a classic positive ground PNP Fuzz Face on there and poof!)   Same thing for the 18VDC taps, which can handle up to 675mA.  The 18VDC taps come off directly from the AC adapter input, with 18VDC going to the 9VDC regulator (wasteful!!)  

Now what about their "Foldback Current Limiting Circuit"?  I googled that term and came up with this: given the Brick's small size, it's probably a solid state circuit breaker, which is used to limit current instead of a fuse.  From a DIY standpoint this is probably the most interesting part.  I'll leave it up to the reader (if you're still reading!) to search on your own for more info, but here's a good article to get you started:

http://powerelectronics.com/mag/power_sspcs_handle_heavy/

So is it just me, or is there not much to the Brick compared to say the One Spot, which is half the price?  You get 18VDC capability and nifty current limiting, but if its 9VDC outputs are paralleled as expected, what's the diff?

[dosmun]

I bought one of the units about 4-5 years ago when it was called the "JUICE".  With the supplied wall wart the thing hummed like crazy.  I got a replacement and same thing.  I tried a 9v Ibanez 200mA wall wart with it and it was fine.  I sent the second back and built my own and never looked back.

[CS Jones]

http://pdfserv.maxim-ic.com/en/ds/MAX830-MAX833.pdf

Hi Dave,
Still winter in Canada?
Clay

[cd]

You're the man, Clay  Thanks for the pics!  Guess I was wrong on the 9V regulator bit, but I had a feeling it wasn't a simple 7809 since dropping 9V like that would just be dumb.  For anyone else who's paying attention (and doesn't know what PWM is), the 830 is an adjustable switchmode regular (PWM).  With PWM it's basically switching on/off very rapidly - so for 9V, if you turn "on" the whole 18V for half a second, then turn it off for half a second, the average over 1 second is 9V.  Of course the 18V has to be "switched" faster than that to trick most things into thinking they're getting a true 9V supply - usually it's done thousands of times per second.  SO, it looks to me that the Brick is a tarted up Onespot/Powerall, with 18V capability.  

Clay: It's actually pretty warm up here right now (60 degrees), on the weekend it was in the high 60s/low 70s.  IME winter is always a possibility until the middle of April, and wouldn't you know it, we didn't really get a spring this year.  BTW if you're in I'll be giving you a call this afternoon.

[Mike Burgundy]

So, to get this right- the Brick is a several-times-9V-plus-several18V-but-not-separated-supply-at-low-power-as-it-is supply? Build a Spyder
I did - in the box of a cheapo 8-out 1-transformer (all the same group) supply. Took some time fitting it all in, but it works a treat and I get 100mA per out - but *silently*...
I could upgrade to heavier regulators, but , well, why? Who uses more than 16 pedals. At once. That don't interfere with groundloop nasties?