FrankenBass audio sample

So... the P pickup sounds pretty good.  It's loud and aggressive.  The J pickup is thin and tinny.  Oh well, I got me self a functional 24 fret P bass now.  Thanks Dan, for not making me show my terrible bass skills.

Franken Bass... The Bridge of No Return

I took the bass to Guitar Center and talked to their Luthier a while.  He recommended just moving the bridge, which is what I ended up doing.  

I took the bridge off, and moved it up about an inch.  It's right on the J pickup, but that's where it needs to be to get the intonation sounding right.  You can see the five holes where the bridge use to be, and there was an impression left in the finish where the bridge used to be.  I simply lined it up so it was even with the old impressions to line it up.  Drilling through finish sucks, if you don't do it right, the drill will skip along the surface and your hole won't be in the right place.

To get around this, I used a small nail to start the hole.  You just position it where you want it, and then tap it a few times just to get through the finish, then pull it out.  Start with the smallest bit you have, and work your way up to the size you need..

The wood colored splotch just under the bridge is the hole for a ground wire.  This wire must be electrically connected to the bridge, which is electrically connected to the strings.  I don't remember the exact reason for this, but I believe it acts somewhat as a noise shield.

Funny story, in high school I used to play music in Will's basement.  There were metal strips running under the carpet, and if you stood on the strip and touched your strings, you'd get shocked.  If you touched the strings and a microphone at the same time, you'd get shocked.  It was cool though, and it didn't affect me in any way in any way in any way.

Anyway, this is the finished bass...  As expected, the J pickup is not very loud, and it's kinda tinny.  The P pickup sounds great.

Maybe next project can be winding a super hot J pickup with a low pass filter... I dunno.

Franken Bass!

I have 2 bass guitars sitting around.  One is an 80's Fender PJ bass that I bought 8 or so years ago.  I tried to refinish the body and... well.. it was kind of a disaster.  I did learn a lot though, so that's something.  Number one... if there's a wood veneer on the body... don't remove it.  Number two... stripping paint sucks.

It may look okay from a distance, but I promise you, I did a terrible job, AND I wired it improperly.  I had purchased a pearloid pickguard to go on there, but the body was some weird size, so I cut my own pickguard.


The second is a fender squier PJ bass that someone gave to my girlfriend because it's a POS with a terribly bent neck.  I tried to adjust the truss rod a few years ago and just ended up stripping out the adjustment bolt.  Oops.  The pictures here don't do the neck curvature justice... imagine the curve you see WITH strings pulling it farther.  The action close to the body was about 1/2''.  I was t

As you can see, it's as straight as Elton John

Last weekend I got all fired up about fixing it, so I decided that I was going to replace the truss rod.  In order to do that, I need to remove the fingerboard.  I was a bit worried about damaging it... but the neck is shot anyway, so I decided to go for it.  I learned that the best way to do it is to use a clothes iron on the steam setting to loosen the glue, and then for VERY slowly to avoid damaging the fragile fingerboard.

I sat there for about 2 hours, playing Deus Ex, refilling the iron as needed, making sure things didn't burn, and prying the fingerboard a bit more every 10 minutes or so.  At first, I was making good progress... the finger board was coming up clean and straight... but once I got to the 7th fret it cracked.  By that point I was able to look under the fingerboard where the truss rod *should* be... but it was completely sealed up!  No way to remove the truss rod.  I kept removing the fingerboard for a while for the practice, but eventually gave up and just pulled it off.

Truss rod?  Where are you?!?

Well... foo on that.  I pulled the neck off of the bass I had refinished and fit right in the neck pocket of the Squier.  Wooo!  I also took the opportunity to take the Seymour Duncan Basslines pickups off of the other bass and replace the terrible stock Squier pickups.

Hooray!  Bass Geeetar!  Well... almost.  After I tried to set the intonation, it was a total wreck.  It's WAY flat.  It's so flat that I can't adjust the saddles far enough to get it in tune.  After the fact, I realized that the new neck is a 22 fret, and the old neck was a 20 fret.  The old neck is about an inch shorter.  I either need to move the bridge, or mod it in some creative way to make it work correctly...

Sovtek Mig-50 repair

Check out this beauty!  It's a Sovtek Mig-50 model 001 guitar head.  If you look closely, you'll notice that they misspelled "Presence".  I was told that this means that it's a rare first issue, which might explain why it doesn't work.

In Soviet Russia, guitar plays you.

This amp has been broken and in the possession of one of my bandmates for quite some time.  A month or two ago, he and his father attempted to fix it, and briefly succeeded by replacing a resistor (so I'm told).  The amp lasted for about 2 hours of play time before it just quit working again.  We're going to open it up and try to figure out what went wrong.

Removed the wooden cabinet.  This is the equivalent of a circuit in it's underwear.  Stay tuned for bare circuits

You can see the output transformer on the left, the power transformer on the right, 5881 power tubes, and the two cans are power supply capacitors.  Behind the output transformer hides 3 12AX7 preamp tubes.


Turning over the chassis revealed the problem immediately.  Two of the power resistors are scorched, and one is completely missing.  There's another less scorched resistor out of frame.  We tried for an hour or so to find a schematic for this amp online, but to no avail. This is the closest thing we could find (http://music-electronics-forum.com/attachments/8148d1266759648-mig-50-oem-full-crop-print-landscape.jpg), but the resistors in the schematic and on the board (R34, R27, etc) don't match the schematic.  I traced the components by hand to figure out which resistors had burnt out according to the schematic.  I found another Mig 50 schematic which the same power supply design which actually listed the power rating for the resistors, and hopefully this is going to work.

R34?!?  Where are you R34?

I have every value of 1/8 watt through hole resistors you can buy, but I don't have any of these mammoth 2 and 3 watt resistors.  Lucky for me, Digi Key exists, and I found all of the parts I needed, and a few spares for about $7.

Now, we play the waiting game...

Fixing tools

I borrowed my Dad's table saw a few years ago.  It came in quite handy while I was building shelves, and even more handy while I was making the 2x12 speaker cab.  On the very last cut I had to make, something went wrong.  The lights in my house dimmed, then I heard the circuit breaker pop.  Then smoke started rolling out of the table saw motor.

To quote Rick Perry again,  "Ooops."

Well,  No matter, I took apart the saw and pulled out the motor.  It took about an hour and some wrenches to figure it out.  I typed the model number into google and found a website that offers replacement motors.

http://www.ereplacementparts.com/

For a mere $200, I can repair my Dad's table saw!  I called up my pops to see if it was even worth it to go through the trouble.  He said it's like 25 years old, (makes sense the motor burned out, especially with the original, dull blade still attached), and that it was a middle of the line product, which it turns out is still quite expensive.  I looked around online and a new equivalent would cost about $1000.  My dad didn't want the saw back, and said that if I replace the motor it's mine!  Wooo!

New motor:  $200
New 10'' blade:  $30
The ability to cut off my fingers accidentally:  Priceless

Anyway, here's some pics.

Disassembled table saw

When I take stuff like this apart, I put the nuts and bolts back where they should be and screw it in a few turns just to remember where they went.  When you go months between taking apart and putting back together, it's easy to forget.

So I started by installing the new motor, and then bolting the chassis and motor mount back to the table.

New Motor!

Re-attach the wires.  This follows standard home electrical wiring.  Black = Hot,  White = neutral, Green = ground.  Notice that one white wire has a connector on it, and one is bare.  The green and black wires have the proper connectors, so this one probably fell off at some point.

Good thing I just happen to have a spare!

I re installed the wiring box and the clips to hold the wires down.

Now it's time to turn it on and make sure everything works before I install the new blade and the rest of the base.

WARNING:  I've learned a few lessons building and repairing things.  Number one:  Be safe.  Always be safe.  You don't want to lose an eye or a finger.  I know I sound like an old codger, but seriously.  I've tempted fate too many times.  Circuits exploding.  Razer blades snapping and flying at my eyes.  I've gotten wires shoved under my fingernails.  Metal shavings into my eye. I've seen people accidentally shove screw drivers into their hands.  In this situation, the table saw has a fuse, so I don't need to worry about electrical hazards.  The only thing left is to put on your safety glasses.  Always put on your safety glasses.

I'm taking to YOU. 

Well what do you know, I turned it on and it ran just fine.  Nothing shook loose, nothing flew at my face. Huzzah!  Now you take off your safety glasses.

Time to install the blade.  This is the old blade.  It's a 10'' blade, and has like 24 or 30 teeth... I don't really know.  As replacement, I purchased a 40 tooth Diablo blade for about $30.  All I know about saw blades is that the more teeth, the cleaner the cut.

25 years of gummy gummy crap

Left:  Old and busted     Right:  New hotness

Odd tip... most circular saws I've used have a reverse thread where the blade attaches.  It's righty loosey, lefty tighty.  I put the blade in, and couldn't resist a Tim Tayler grunt or two.

Add caption

I bolted the lower part of the base back on, and took in all of the awesome.

Well, I have no projects in mind yet... so I guess it's gonna be a while until I put it to the task.

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.

Repairing a Hartke bass amp

Here's the story... right before Battle Toys first show, our bassist blew out the speaker in his Peavey combo amp.  We would have been left with no bass, luckily our friend and recording engineer, Chout, from the band Small White was able to loan us his Hartke bass head and cabinet.  The head has two 1/4'' outputs for speaker cabinets but one of them was busted.  I decided to thank Chout by repairing the outputs on his bass head... with his permission of course.

Front view

Holy crap, look at that monster transformer.  Also, you can see the two output jacks, just to the left of the fan.

I am a sucker for things that light up...

Speaking of lighting up... check out the glowing 12AX7 pre amp tube.  It's a little guy, but he gets the job done.  This head has the one tube pre amp, in parallel with a solid state pre amp, and a solid state output stage.

I wanted to get that header out of the board so I didn't have to hard solder the wires.  I tried to de-solder it, and pull with a needle nose pliers.  The board snapped, and luckily, out popped the header.  Woooooo!

Bloody Mary... because I don't need a reason.

Left:  Old and busted.   Right:  New hotness.  If there are any eagles eyes out there... you'll notice that I hooked the wiring up wrong on one of the jacks.  To quote Rick Perry... Oooops.  Luckily I ohmed it out before connecting it and discovered the problem.

Well, here ya go.  I connected the output of the Hartke to the 8 ohm speaker in that Crate amplifier.  Connected the oscilloscope to take a look...  Voila!  We have sound!  Both output jacks work!  All glory to the Hypnotoad!  

Oh wow... I just noticed all of the junk on the floor.  Is that a 3.5'' floppy disk?  What year is this, 1992?  

As always... questions?  comments?  Email me at soundularelectronics@gmail.com