Dumb, dumb, dumb

[Mark Hammer]

So, I had my Tycho Brahe Octavia tweaked to sonic perfection, but it was not installed in a chassis.  I unsolder all the temporarily attached wires and whip up a box with stereo input jack, mini phone jack for external power, stompswitch, the whole nine yards.  I legend the box and clearcoat it.  Then I wire it up.....and....nothing.

Drives me crazy the whole weekend.   Then late last night I realize that I was looking at layouts and schematics for a negative ground Octavia (PNP->NPN->NPN), and what I had built was a positive ground unit (NPN->PNP->PNP).  Flip the battery wires around and bingo.  My face was red...but not as red as my ground wire should have been.

[Auke Haarsma]

Ha, you keep learning every day 

[petemoore]

  Might seem dumb to you, but I'd like to read a bit more about what was involved in 'tweeked to perfection' in your case.

[R.G.]

That just goes to show how dangerous a little knowledge can be. An amateur like you can't really compete with a pro like me.

I could have worked that up into burning down the house around me; with a bit more effort, I would have started a grass fire that would have destroyed the neighborhood. 

And let's not talk about debugging the solder side of a board which has no ICs in the sockets on the top side. 

It happens to all of us. 

Hmmm. That makes me wonder how bomb defusers get their licenses. The lab work must be interesting.

[Ice-9]

I think the only lab work bomb diffusers get is a saying from the tutor, which reminds them thus.

"Black to black, red to red and blue to fook."

but really when a problem arises it is so easy not to spot the obvious and spend hours debugging something that is staring you in the eye.

[Mark Hammer]

And that, my friends IS the moral of the story, or at least one of them.

1) Doesn't matter how many pedals you've built, or whether other folks think you know what you're doing, even "experts" mistake the obvious.

2) NEVER exclude the obvious when troubleshooting.  That doesn't mean it WILL be the obvious, but you have to know it's NOT the obvious first, before moving onto other potential sources of nonfunctioning.


The first moral reminds me of some literature I've since stopped following in the last 15 years, but I know there was a bunch of research regarding the manner in which "experts" can often see things that aren't there.  It is often referred to as "false recognition".  I gather it occurs because experts have rich knowledge about what they expect to see in certain situations (specifically, those areas they are expert in), and confuse what they were reminded of with what actually transpired/existed.

The second moral reminds me of "Morgan's canon" (http://en.wikipedia.org/wiki/Morgan%27s_Canon).  This case is a transposition of that canon: Never assume a pedal's nonfunctionality is due to more complicated exotic causes until you can successfully rule out more mundane and embarrassingly simple (and obvious) causes.  In this case, Mr. Genius here did not successfully rule out "You got the battery in backwards. moron!"

Pete,
The "tweaking to perfection" was simply the addition of a 330R resistor in series with the 1k pot.  The circuit needs a bit MORE than 1k, rather than a bit less (which is too often typical of modern day pots).

[frank_p]

Hmmm. That makes me wonder how bomb defusers get their licenses. The lab work must be interesting.

http://ca.youtube.com/watch?v=JBfjU3_XOaA
Ouch !

[R.G.]

The second moral reminds me of "Morgan's canon" (http://en.wikipedia.org/wiki/Morgan%27s_Canon).  This case is a transposition of that canon: Never assume a pedal's nonfunctionality is due to more complicated exotic causes until you can successfully rule out more mundane and embarrassingly simple (and obvious) causes. 

The medical profession here in the USA says that this way: "When you hear hoofbeats in the hallway, don't go looking for zebras."

[drewl]

So I'm fixing this guys Fender clone amp and I realize the jacks are wired backwards.
I look at channel 2 and rewire ch1 correctly......until I realize ch2 was wired wrong also.....
DUMB DUMB DUMB DUMB.......

[drk]

just now i was finishing a preamp in my guitar, i had already tested the circuit so i knew it worked so i just put everything together and close the pickguard. tried it out and well, didnt worked..  i started thinking about what happen, thinking about really crazy 'problems'... after opening it again, i realize i had the wires in the switch wrong, changed them and it works now lol 

[drewl]

I wired up a bunch of cool mods to some guys guitar, phase switch, series/split/parallel switch all kinds of great ideas....then I realized the pickup wire colors were different from the diagrams I was using.....
DUMB DUMB DUMB.....

got zapped with 300v last night by a Marshall.......(my son distracted me).....DUMB DUMB DUMB....
I could go on all day.

[Boogdish]

At work we had an "amp camp" over the weekend where guys bring in amps that had been giving them trouble and we help them fix them.  One guy had an old Dual Showman that he said just wouldn't power up and he was all ready to install a new power transformer in the thing. First though, we traced connectivity through the cord to the fuse to the switch to the transformer, then we tried turning it on and we were actually seeing voltages on the tubes.  Turns out it was a bad bulb in the pilot light, the amp worked fine (needed new filter caps).  He was really embarressed, but then I told him about how a week ago I had installed PCBs in a switching pedal without their IC and a few months ago I was so puzzled why I was getting bad voltages on the tubes of an amp...before I had put the tubes in.

[~arph]

Was working on the breadboard for over an hour a few days ago. Nothing I did made a change. So I quit. Five minutes later I realize I hadn't plugged in the adapter. I should have at least checked the supply for my opamps.. 

[runmikeyrun]

I like this thread- i dont feel so stupid!  I plugged in an old pedal for sound samples the other day and couldn't figure out why it was really bassy, low gain, and generally sounded like crap. I cursed myself for obviously not doing something right somewhere along the way, and how could it have broken when i didn't even use it!

Plugged it in again last night with a different guitar cable and it worked like a charm...

[Mark Hammer]

So, um, I guess this is our "blooper reel", eh?

[jacobyjd]

I've done the reversed ground thing at least 3 times in recent memory...gah...

My favorite one is when I'm populating a board in which I've mounted all the components, I go crazy and solder all the pads before realizing that some of them were empty--no offboard wires yet! My eyesight is kinda crappy, but that's no excuse for lack of observation :-P

Also, on two separate occasions, I marked and drilled enclosures. All the holes were aligned with precision, and I was thrilled with my work...until I realized that I'd drilled all the control holes in to the lid of the box instead of the box itself...hello spaghetti trap...dumb, dumb, dumb...

[Ice-9]

A little while ago i spent quite a bit of time troubleshooting a pedal i was working with that originally worked, but i was changing a few things to alter its charicter. After about an hour testing i realised that my guitar was plugged into the output jack and the amp into the input jack. Ahh thats why i got no sound. 

[Mark Hammer]

Been there, done that, bought the t-shirt, wore out the t-shirt, used it to polish the car.

[DougH]

A little while ago i spent quite a bit of time troubleshooting a pedal i was working with that originally worked, but i was changing a few things to alter its charicter. After about an hour testing i realised that my guitar was plugged into the output jack and the amp into the input jack. Ahh thats why i got no sound. 

Another fun one is when you forget to plug the speaker into the amp...

(At least I found out my amps are pretty robust. I ran them for 15-20 minutes unloaded with no problems...)