Thursday, June 26, 2008

Week 2 Wrap-up

Congrats to everyone who got their Fred working... a world with more Freds is a better world. If you spent time finishing him off, mounting in a case etc., please bring him with you for everyone to see. If you ran into problems, bring him back and I'll see if I can do some troubleshooting. True fact, tho, is that sometimes a circuit-bent project just doesn't work... chips blow, or the magic smoke comes out. Sometimes it's just time to move on.

Besides more practice w/ the mechanics of making, the idea of changing the resistor/capacitor combination to change the speed of the circuit is something we'll be using a lot. More schematic practice comin your way soon, too.

Coming up this week: amplifiers. The oscillators we'll be building won't drive a speaker directly, so we'll need something to amplify them with. You’ll need your speaker, and fresh 9v batteries (the Victorian Synth project is pretty tuff on batteries; pick up 2 if you can so you have a spare). If you've got a kit bring it, it has almost all the parts you’ll need. Still waiting on some components, but if I don't have kits for everyone by Sat. I'll have components so you can build the amp.

Folks have been asking about tools, I'll try and post a list of recommendations in a couple days. Got a couple other questions that I thought I'd post:

Q-- I connected [Fred’s] speaker wires to a line out (1/4 inch output jack) and it doesn't work with my guitar amp, all I get is static coming trough the speaker. I plug it into my small "Smokie" amp (powered by a 9 volt batter, small speaker) and it play but with slight static. If I clip it to a speaker, hey! No problem there! What's the cause of this? Any ideas? Do I need a pre-amp?

A-- fred puts out a speaker-level signal... which means that it's hotter than line level, and often will overdrive/distort if you connect to an amp.

we’ll do something with voltage dividers sometimes soon. [update: see Voltage Dividers] in the meantime radio shack used to carry a cable for connecting the headphone out of a walkman to the line in of an amp... if you could find something like that it might help. [followup: it did]

Q-- ...I saw you troubleshooting that fred board while we were wrapping up. What were you doing? I have a bunch of non-working guitar pedals... Do pedals typically "break" because of loose solder joints? How do I check connections?

A-- a lot of basic trouble shooting is checking continuity of connections... making sure things that should be connected are, and that things that shouldn't be aren't. i was probably using the continuity checker on my voltmeter... basically it just beeps whenever the probes are connected together. sometimes solder joints look good, but you check 'em and they're not... othertimes, a little blob of solder has made a bridge between what you just soldered and some adjacent component.

pedals often go out due to broken connections or controls... the battery connection in particular, since it gets yanked on; likewise the switch since it gets stomped. so those are good places to start checking.

a cheap voltmeter is pretty handy, i use that continuity test all the time. i’ll go over the basics of how to use one in a future install.