Power Supply Project in progress (pictures)

343 Salty Beans · August 07, 2006, 04:09:16 PM

So I decided to start working on this project yesterday with a friend. We plan to finish sometime today or tomorrow. We built these using this vero layout:

http://i6.photobucket.com/albums/y240/hockyfreak5/PowerSupplyschematic.gif

This is a picture of my dinner last night

, our nice granite countertop, and the mint box enclosures I decided to spiff up about halfway through the project. The enclosures each have 2 coats of black and 2 of clearcoat.

As you can see, I plan to run 4 9v plugs out of each enclosure. I thought about 5, but I didn't want to overtax my supply.

I decided to superglue washers onto the holes to make it look a little nicer...unfortunately, this was after my crappy drill job where the drill bit jiggled all over the place. My finger has a nice bloody line where the bit bounced off and ate some of my skin

I think it looks alright, though. One enclosure has a blue LED power indicator, one has a red one.

A closeup of the first finished board. It hasn't actually been tested yet, but I'm about 99% positive it will work (it's not the most complicated circuit, and I've triple-checked every possible screwup.)

It fits!

as you can see, the jack and the plugs aren't soldered on yet. My friend works at ratshack, so he has a 30% discount, and I don't feel like waiting a week for my parts. I decided not to add a switch to turn the power supply on and off; i couldn't really find a use for it. I thought about adding a starve switch for 1 or 2 of the lines out, but I figure I'll put it near the end of the line if I decide to do it. Speaking of a starve switch, what is a good voltage to starve your pedals at? I'm asking for an approximate because I don't really know what effects I'm gonna starve (if any).

My temporary workstation. You can see my Dremel, my most useful and prized tool and my Dr Pepper, which is my lifeblood. Normally I work out in the garage, but it's just so frakkin hot lately...

My only two questions are advice:

1) should I put starve switches in? if so, what voltage should I reduce the lines to?

2) should I aluminum foil the inside of the enclosures to keep any hum-inducers from getting out? I'm already planning to filter each line individually, but I'm not sure if the aluminum boxes will block the noise signals entirely.

Thanks to Ge_Whiz for alleviating my fears and giving me a little more electronics knowledge. I'll post final pics in this thread when I'm done.

jimmy54 · August 07, 2006, 05:13:19 PM

I built one of these a few months ago using the same vero layout. I used the 12v, 1A adaptor from my Rotosphere to power it. Measured 9v DC from the other side, everything seemed to be OK. I used it to power my 5-in-1 effect (which runs OK with my 9v DC brick). After about ten minutes the effect went off. My 12v adaptor was dead. Presumably the transformer inside must have burnt out (it was quite hot to the touch). Dont know what caused it as I would have thought 1A was enough to power the effects (orange squeezer, sparkle boost, TS808, Rebote 2.5, fuzz).

Torchy · August 07, 2006, 05:15:35 PM

Was the rotosphere adaptor ac or dc output ?

jimmy54 · August 07, 2006, 07:09:28 PM

ac

Torchy · August 07, 2006, 07:36:05 PM

Im using a 15V AC adaptor on mine, powering 4 fx and its been good for over a year ... hmmmm.

343 Salty Beans · August 07, 2006, 10:31:20 PM

odd.

I was finishing up soldering the plugs onto the ends of my power outputs when suddenly my multimeter decided to read 0. I made sure my (DC) power supply I was running it off of was working smoothly...it measured 14v (it had measured only 10v from the same outlet just a few hours ago) for some reason. I opened up my enclosure and the L7809 chip inside was burning to the touch...I'm gonna measure it, but I think the chip is dead.

Any thoughts on how I might prevent this from happening again?

EDIT: once I opened the case and turned it on to measure the output of the 7809, the circuit started working again. I then noticed that the heat from the heatsink on top of the chip had eaten through the PVC electrical tape I had placed to prevent a short. Hmmm...

the PCB is already mounted with hot-glue, and the 7809 won't lie flat unless I resolder it. BUMMER.

jimmy54 · August 08, 2006, 02:43:19 AM

Salty, you need to use an AC power supply for this circuit, not a DC one.

343 Salty Beans · August 08, 2006, 01:58:56 PM

I don't believe it will matter. The diodes convert AC to DC, but not vice versa. They'll be there for reversed polarity protection. Now that I fixed that short, the power supply is doing great. I left it on for an hour last night to see what would happen, it wasn't even warm.

Torchy · August 08, 2006, 03:03:45 PM

The diodes are arranged as a bridge to rectify ac. If you supply dc then the diodes in the positive conduction path stay forward biassed (conducting) and the rest are not conducting. There is no polarity protection here - not that its required as its an ac supply thats intended. Read up on how bridge rectifiers work (theyre quite simple).

Stompin Tom · August 08, 2006, 03:22:21 PM

Salty, do you have finished pics yet? I'm curious to see how the mint tin works out for you... seems like a good use for one of those.

birt · August 08, 2006, 06:20:38 PM

stupid semi-offtopic question. is the DC voltage you get after a diode rectifier higher than the AC voltage you feed the rectifier with? like 6Vac becomes 9Vdc? i might have picked up some numbers somewhere and mixed things up in my head..

343 Salty Beans · August 10, 2006, 02:07:30 AM

Quote from: Stompin Tom on August 08, 2006, 03:22:21 PM
Salty, do you have finished pics yet? I'm curious to see how the mint tin works out for you... seems like a good use for one of those.

I've got one finished...then I took two days off and headed to the beach. Plus my camera is in the mountains with someone else right now

but when it comes back, if I don't have the second one finished, I'll at least post pics of the first. It turned out great, it's NOISELESS with my current pedal configuration, and it doesn't even warm up, even when I'm running two rather current-consuming pedals off of it (an ME-50B and a CE-20).

To come to the subject of the mint tins, they work super well, as long as you isolate your circuitboard from the tin (I did it with cardboard...I'm so high-tech

). I finished the first, bigger mint tin; I'm confident the smaller one will work out just as well.

Stompin Tom · August 10, 2006, 10:18:19 AM

Awesome... thanks. Looking forward to pics.

By the way, I can't drill those tins worth crap either... not that yours looks bad, just a little uneven.

343 Salty Beans · August 10, 2006, 09:51:28 PM

hahaha...actually, they do look bad.

it would be nice to have a drill press, but it's something you just can't fit in a college dorm room.

343 Salty Beans · August 15, 2006, 01:59:21 PM

Okay, I finally got the second one on the table and have it mounted and the jack soldered on. Naturally I tested it with my DMM to make sure that it actually worked.

And it...didn't?

Here's where I'm confused. The wall-wart I use to power the whole project shows 10.5 volts when I measure it without any load. Once I plug it into the damn thing, it measures 2.36 volts. I'm measuring right off the jack itself. Now the wall wart has a supply of 500mA, so it's not like it's being overloaded or anything, is it? What do you think could be wrong?

PS: The 7809 chip has an output of only .74 volts, too.

If I had to guess, I'd say it was my 220uf cap...I had to solder 2 100s and a 22 in parallel because I was all out. I'll replace it and see what happens then.

343 Salty Beans · August 15, 2006, 03:16:15 PM

Okay, another update.

Turns out when I resoldered the chip (I had to take it out of the socket, it was too tall on the board), I moved it down one strip on the board. silly me

But I'm gonna need a more powerful adapter before I finish it. This one doesn't quite put out enough voltage; it's ten volts without a load, once the load is on, it's reading around 7.8 volts BEFORE the 7809 chip. After the regulator, I've got around 5.5 volts for each line out.

Whereas my other adapter put out around 14.8 volts without a load on it.

Tim to go find an adapter

Stompin Tom · August 15, 2006, 05:46:24 PM

Just in case anyone looking at this thread didn't see this in the spyder thread, RG's article helped me understand what exactly was going on in one of these things:

http://www.geofex.com/Article_Folders/Power-supplies/powersup.htm

343 Salty Beans · August 16, 2006, 03:21:17 AM

Thanks man...

the big problem I have with this thing is that it creates ground loops. Ground loops mean loads of power supply hum. I believe it was Mark Hammer's article that suggested breaking the shielding wires in my patch cables or making individual power supplies in a single box with a fun transformer trick. I think I may do the spyder supply then give one of these to my guitarist and sell the other one for 20 bucks...

anyways, PICTURES. I'm supposed to be posting those. Unfortunately, I still have yet to entirely finish the second supply. It doesn't quite fit in the smaller mint tin

I'll probably need to use an altoids box instead of that 'everest' one. I think I'll switch them tomorrow and make the new enclosure if I have time...until then, I'll try to get pictures of the finished one tomorrow.

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Power Supply Project in progress (pictures)