Effects pedal power supplies

So I got all of these guitar pedals I've been building, but powering them is an issue.  At my house, I've actually been using a variable power supply thought I bought on eBay a few years ago.  It serves it's purpose, but I use the power supply for other things, and sometimes I forget to disconnect the pedals... oops.

Quad power, baby!

Anyway, this is how you can re-purpose old 9V power supplies for FX pedals.  I got this honker here out of the trash.

This is what you want to look for, a supply that will deliver 9V and at least 1000mA.  This is a typical connector configuration, with the positive voltage on the center pin, and the negative voltage (ground in this case) on the sleeve.  Most effects pedals are exactly the opposite.  Using this power supply as is on guitar pedals will, at best, not work.  Worst case scenario, you damage your expensive pedal, in a glorious flash of smoke, and a beautiful electrical fire.  No one wants that.

Lucky for us, switching the leads is easy, and takes only a few minutes.

You will need:

Solder Iron
Wire cutters/strippers
Solder (I recommend lead free solder.  Lead is poisonous, take precautions if you use it.  A little lead solder here and there shouldn't hurt you, but prolonged exposure is not good)

Heat shrink of various sizes. I bought a huge pack at Ax-Man surplus for less than $4.00.  It's lasted me for more than a year, and the heat shrink also makes great cat toys.  Seriously...

Voltmeter (a cheap one will run you about $5.00.  A high quality meter can cost a $200 or more.)

Optional:  Hot air gun to shrink the heat shrink  (a hot air paint stripper works best, hair dryer will work, but you can also use a solder iron)

First... plug in your power supply, make sure it works by measure the voltage on the connector.  Use the red lead in the center hole, and the black lead on the sleeve.  It should read 9-12V.  Wait a minute... why is my 9V power supply reading 12V?  Well, when there's no load (I.E. Guitar pedals) sucking power, the voltage can be higher.

So, you power supply works?  Great!  Unplug the supply, and continue monitoring the voltage with your voltmeter until it reads 0V.  These power supplies can still have energy stored in them, and you can get shocked if you don't let the power supply discharge.  Power supply doesn't work?  What I usually do is snip off the wires close to the plug.  You can use the connector and wires on your variable power supply, like me!  Or you could use the extra length of wire/connector to extend the range of a working power supply.

Second.  Cut the wires.  I usually do this 3-4'' from the connector.  Pull the two wires apart, and strip a small amount of insulation from each wire.  Using your soldering iron, place a bead of solder on each of the exposed wire tips.  This is called "tinning the leads".

Next, the miracle of heat shrink!  Seriously... you need heat shrink.  It's far superior to electrical tape.  Since I'm going to be soldering the wires back together, I need to put the heak shrink on before I solder.

Do you notice that only one wire has a white strip on it?  This is how you can identify the correct way to re solder the wires.  It's nice to have a third hand, or a clamp for this part.  I just popped the connector end into a pedal to hold it on place.

Solder the wires together by melting the beads you applied when you tinned the wire, do it as fast as you can so you don't heat up the wire too much, and then just hold the wires in place until the solder sets.  It's usually only a second or two.

Once your wires are re soldered, you can move the heat shrink into place and use the collar of the solder iron or a hot air gun to shrink it.

Slide the heat shrink over the solder bonds and use the solder iron to shrink  them.

A larger diameter piece of heat shrink holds the two wires together

Plug in your supply and measure the voltage on the connector.  If you put the red lead on the sleeve, and the black lead in the center hole, your voltmeter should be the same voltage as your first measurement.

That's it.  It's a 5 to 10 minute endeavor, and you can save yourself the cost of purchasing the expensive effects pedal power supplies.

Repairing Yamaha Delay Part 2

So... after a few weeks off I finally have some more time to finish continue working on this Yamaha delay unit...

Why U no work?

So... we left off with me going to buy fuses...

Alright, get this... I go to home depot to buy fuses, and I tell the guy I need some 3/4 amp fuses.  He doesn't  have any in stock, so he hands me a box of 1 amp fuses and says they'll work just fine...  seriously...  he doesn't even know what I'm doing with it.  That 3/4 amp fuse might be protecting the whole unit from exploding in a giant fireball of epic proportions, raining death and radiation to the entire United States and for some reason, parts of Brazil.

Thanks a lot, Home Depot guy

Or maybe I'm just being over dramatic... whatever.  I bought 1/2 amp and 1 amp fuses.  Go figure, the 1/2 amp fuses blew right away.

Turns out the 1 amp fuses didn't cause an explosion (you win this round, Home Depot guy), but a heatsink was getting hot enough to fry an egg, and that tends to indicate a problem.  Sure enough, I found some nifty voltage test points on the board... there are 8, +15, and -15 volt rails, and the 15V rail was dead.

Awww yeah!

I'm no expert on power supplies, so I tried to find a schematic to see what I'm dealing with.  I guess those dudes at Yamaha don't want a "non Yamaha certified" person to repair their stuff... go figure...

I guess I'm on my own...

Well, after an hour mapping out the power supply and testing voltages, I still had nothing.  Of course I measure the one that was working, and the one that wasn't (which is a mirror circuit with PNP transistors).  No dice... the voltage was sagging all the way up the power supply.

Yup... BJT fo life

So... lets cut the rest of the circuit out... find out what's failing.

What's a jumper or 2 between friends?

I guess that did the trick... the power supply is actually at -15 volts, and the other end of the circuit which it should be hooked up to is shorted to ground...which means my problem is the rest of the circuit.  Luckily for me, every other part of the circuit had it's own jumper connecting it so I just kept cutting until I found the offender.  A tantalum capacitor!  My mortal enemy.

You see, unlike electrolytic or ceramic capacitors, which fail open, tantalum caps fail shorted.  I just pulled it out and reconnected that section to the -15 rail and voila!  

And then... fail...

A different tantalum cap blew.  And another...

Oh well, I wasn't sure what they did, so I just pulled them out.  I tried to replace all 3 with ones that had a higher voltage rating, but for whatever reason, that circuit really doesn't like those caps...  Every time I cut one off, the circuit worked, and as soon as I tried to replace them, it would fail... so screw it, I took them all off.

Oddly enough, when hooked up a guitar, it worked again... hehehe. It turns out they're just some bypass caps to smooth out ripples on the power line, so hopefully there isn't any noticeable hum, or maybe I just accidentally created the greatest rack mounted analog delay of all time... we'll just have to find out.  

I'll have to get this back to Chout at the Fortress of Desire and see how he likes it!

Questions? Comments?  Want to tell me how great I am?  

get a hold of me at soundular-electronics@gmail.com

P.S.

For all you aspiring electronics people out there... even pros make mistakes.

Don't see it yet?  Let's look closer

You have brought shame to Yamaha

You see those three grooves cut into the board?  Someone screwed up, and after this PC board was made, someone (or a machine, it is Japan, after all) had to go through and make 3 cuts in EVERY SINGLE one of these.

I only recognize this because that's exactly what I had to do to fix my drum light boards... derp...

Repairing a Yamaha Analog Delay E1010 Part 1

So, I got another repair request from a friend of the band and recording engineer, Chout.  He bought a yamaha rack mounted delay unit... turns out that the front Input jack has the tip of a cable stuck in it.

There is another Input jack on the back of the unit, but the two jacks are wired up such that the jack with the broken tip in it has priority.

This is a diagram of the front panel input connector.  Basically, pin 1 is the tip of the cable (signal) and pin 3 is the sleeve (ground).  When no cable is plugged in, pin 2 connects to pin 1, and when the cable is plugged in pin 1 disconnects from pin 2.  The back panel input jack is wired to pin 2.  This means that when a cable is plugged into the secondary input, the unit will use that signal, but if a cable is plugged into the main input, the secondary is disconnected and only the main signal will be used.

This works great, until a cable tip gets stuck in the main input jack, rendering it useless, and also effectively disabling the secondary input.

Begin the tear down!

Oh, I guess I'm not supposed to remove case...

Or... maybe I will...

Well... there's your problem.  But how in the heck to I get it out?

Ahhh... it appears the front panel is just a facade.

Well... some poking around revealed that I'm not going to get that tip out of there without breaking the jack, so I hopped on Digi Key and found myself a suitable replacement.  I also decided to jumper over the input switch with an alligator clip, but the thing still didn't work.

Alligator clips for the win

Just when I was going to give up, I noticed these...

Fuses!

The picture doesn't really do it justice, but the two 0.75A fuses were very milky white... and I couldn't see if the fuse wire was still intact.  I pulled out the trusty multimeter and it turns out both of them are blown.  Something must have shorted in this delay unit, and hopefully it wasn't me.  Either way, I'm off to buy some fuses.

Ibanez Tube Screamer replica

So... I was at a friends house and he had an old Ibanez tube screamer pedal.  I sinned and coveted my neighbors belongings... sorry Jesus.

I went onto the ole interwebs and found myself a kit from General Guitar Gadgets.

Boom!  Parts ship... arrive at my house... a little solder job later and it works.  I decided to make this pedal pretty and pay somewhat of an homage to the original.

Bring on the green paint!  I gave it a round of grey automotive primer and then a whole slew of green enamel .  I popped it in the toaster oven for an hour or so to at about 350F to hasten the curing time.

Since it IS a tubescreamer... why not decorate with some tubes?  The lady helped me photoshop a vacuum tube photo into a whole page of decals.  I included some text in the decal page too...

Apply the decals, about a half a spray can of clear enamel.  Another trip to the toaster oven... and Voila!

Awwwwww yeeeeahhh!  Ain't she pretty?

The Minneapolis band Battle Toys used this pedal to record their song "Idols".  Okay, it's not because I'm some sort of pedal god, it's because that's my band... heh

Here it is inside the Terrarium with a POG pedal and the Battle Toys.