AMZ.... a lesson learned

[axeman010]

So.........

I have friend who wanted a booster pedal and also wanted to get into building his own pedals.

I had already built two AMZs (due to the first one being stolen) and thought this would be a good starting point for him. I ordered all the bits for him and rather than using the 2N7000 that I used for my builds (off the shelf from maplins) I got him a BS170 as recommended on AMZ's great web site.

We both had the day off and after a proper breakfast (bacon, eggs, waffles, coffee etc.) he sat down building the thing under my "guidance" (he was a soldering virgin) . The air was buzzing with eager anticipation. It should be ready for the jam tonight. While he soldered I drilled the case and passed on my meager words of advice. It was all going swimming well. His soldering on the vero board (is it still called that now they don't appear to exist in the UK anymore?) was neat and tidy. Approaching the finish line we had the inevitable "will it work first time" conversation. You know where it's going from here..... It didn't!!! So we checked everything 4000 times and I got my booster out as a reference point. It all looked the damm same. So now we are into part failure territory (wrong wrong wrong wrong).

My other half came home with our daughter and now I am the proverbial bear with as sore head. Do you have to do that and why does the TV have to be so loud? Can't you see I'm working here?

My friend went home to get his gear ready and I carried on resolute that it would be working in time; this was a matter of pride now. It was not working for the Jam.

Fast forward to several rocking tunes and some Stella later and arriving home with the "thing won't beat me head" on. I toyed with the idea of going to bed and a fresh pair of eyes in the morning..... Like that was going to happen.

Then it happened, an epiphany...........the danger of making assumptions!!!!! Within 5 mins of being home and picking the thing up.

Things that look the same and do the same job are not all the same. That is why the good people that make the parts we all use publish detailed info about their parts on the Webb!!!

in short the 2N7000 and the BS170 do not have the same pin layout and I was a Pratt to assume that they did. It possibly took longer for the iron the heat up than it did for me to realise my mistake. Now it works like a dream.

Hopefully my friend will not have been put off by my stupidity and will continue along the path.  I have learnt a lesson that will stay with me forever.

Here endith today's lesson from the dim wits school of pedal building!!!!

Axeman.

[bioroids]

LOL nice story, and it comes with a lesson too!

Sometimes you just need to take a break to get the ideas flowing, specially when you've been debugging for hours something that doesn't appear to be broken but doesn't work either!

Regards

Miguel

[Morocotopo]

Been there, done that.

Good it worked in the end.
This hobby teaches us to think and work logically and methodically, don´t you think? Cause when we don´t, it kicks our asses and things don´t work...and no matter what "in the heat of the moment anger" solutions we desperately try, it´s usually operator error!

Morocotopo

[aron]

I got caught with that too. Luckily I used a socket and coerced the leads to match.

[Cthross]

I did the same thing as well when  I used an NTE compatible device and was stumped. Then after searching I found a similar post to yours that fixed the problem. Now I always check the pinouts first. A good lesson learned.

Chris

[gutsofgold]

That glorious moment when you realize what you did wrong, and confirm that it really was the problem, that could be one of the most refreshing feelings. I spent five hours on a electrical engineering lab once only to find out the ENTIRE BATCH of 555 chips I was using had been zapped to death. Boy was my face red after that.

[earthtonesaudio]

It seems like no matter how many times I read the "debugging" FAQ's out there, I always seem to find a way to learn first hand what not to do...
It's as if there's some law of physics that makes it so you can't see the reversed battery leads until you've checked every-single-other-thing at least 3 times.  Or that the guitar is not plugged in.

[gutsofgold]

there is a law but it's not by physics, it's by a guy named Murphy. 

[aron]

My favorite one was always not grounding the op amp. Now I don't make that mistake anymore, but still.....

[trendyironicname]

i built something for a friend and we plugged it in, nothing.  I immediately started looking over traces and the schematic. No sound.  30 minutes later. No sound. Long story, short.  The guitar volume needs to be up for sound.

[demonstar]

I always keep forgetting to put the ICs in their sockets. 

[Paul Perry (Frostwave)]

Well, I built a batch or ring modulators this week... and no go... turned out, at one place on each board, I had soldered in a CA3080 instead of a TL072.

Well that was a LOT of legs to cut off, holes to clean out... thing is, I have to make a real effort to see what a chip is, so unless I definitely have the right tube in my hand..

[nokaster]

I always keep forgetting to put the ICs in their sockets. 

been there, done that!

[nebucanazza]

I once spent 2 days resoldering and checking my first build, but somehow it wouldn't work at all. Finally I found that the output jack's tip was grounded too. Replaced the jack only to find the same problem was still there. Finally I realized that I had drilled the hole too low and the jack tip connection was touching the enclosure   A piece of insulating tape fixed the problem in a jiffy but man,was I pissed!

[jayp5150]

It took me two days to debug my jfet matcher. lol. I was ticked since it was holding up my phaser build. Ok, not two full days, but a good, hard look, 18 hours of idle frustration, then another look.

Anyhow, built it on vero, and when I took that second look, I hadn't even soldered one side of a jumper. It was just poking out the back (already clipped, so it blended in).

Felt like a moron, but it worked fine after that.

[rikkards]

For some stupid reason when building my BSIAB2, I used the Vero layout  as being from the bottom of the board rather than from the top (I said it was stupid). I didn't realize until I was about 1/2 way through and kept going. It was when I got to the IC for the OpAmp that I realized what moving on was going to entail as the IC was now backwards. DOH.
What did I do? I flipped the leads upside down on the IC. 

[nag hammadi]

someone once said something to the tune of "a lazy man works twice as hard"....

once i was so pissed at a bsiab build that i couldn't get running that i actually built another one ENTIRELY POINT TO POINT because i blamed the PCB.

yep, i sure did.  it took two days, a huge expensive enclosure (well, $24 or so anyway), and a bunch of post build alcohol for "decompression".

yes, it worked.

then i noticed that the trim pot looked slightly different on the p2p version.  that's when i realised that i used a 100 ohm trim on the first one instead of the 100k i was supposed to use.

all i had to do to find that mistake was to build an entire new unit POINT TO POINT.  because that makes sense.  because, you know, it was the PCB's fault - certainly not mine.  i read books and listen to talk radio, after all.

[R O Tiree]

I recently built a TS-808 clone and was working from a ratty old jpg of the schem on a board layout of my own design. Completely missed the decimal place on the two caps in the tone circuit so, instead of .22µF, I slapped two 22µF caps in there. Unsurprisingly, although I was getting a beautiful, softly clipped signal out of the first half of the opamp, there was just a very small, fuzzy triangle-shaped wave out of the other half. Spent the whole of the rest of the evening pratting about with the oscilloscope, checking joints under a jeweller's loupe, ran a wire from my last good signal to the output buffer input - golden, tried every trick I could think of... Next evening, a nice cup of tea in hand, I went through the circuit again and it dawned on me that a chuffin' great cap directly to ground was going to do nothing more than bleed the whole signal direct to GND.  Off to tonepad et al to check their versions of the schem and sho'nuff, I'd been a muppet.

1. Walk away and chill out for a bit to let the mind go into free-wheel.
2. Check the schem against your board part by part, ticking them off as you go, checking for value, orientation and pinout. If you can get hold of another version of the schem, that can make something leap off the page at you.
3. Get yourself a jeweller's loupe. Actually, this is quite depressing, because your beautiful, shiny joints look like the dark side of the moon and your tracks look like they were drawn with a child's crayon. Look for dry joints, missed joints, whiskers of solder joining tracks where they shouldn't, etc.
4. Check you got the battery the right way round.
5. Check that you connected your signal source (guitar? signal generator?) into the INPUT, not the output. Easy to mess up, because we like our inputs on the right (for some reason) but they will be the other way up when we're building/de-bugging.