walking around blind

[josh]

Good morning everyone.

So, I've been a member here about 3 months or so. I've successfully built about a dozen stomp boxes before I was pointed to this much larger world. So far I've successfully built the GSSL like everyone else. Now I've spent more money than I have on my next 4 projects all at once because I overdo everything.

Anyhow.....

Here is my problem: I don't know what I'm doing. I am painting by numbers and that is all. I have no clue why I am doing things this way or that way. I am a robot. It's not too bad if the end result is a piece of useable gear right? No. I can't do that. Right now I really am scared to finish wiring up my GIX preamp because I know I could hurt myself very badly, and I know if I wire the case I'll not be able to resist powering it up. So there it sits, and I've moved on to finishing a Paia quadrafuzz and stuffing my Mnats 2-1176 boards.

Where can I learn about this? Online, not online, I don't care. Throw it at me please.

My schooling background does include 2 basic electrical engineering courses (my degree is in industrial engineering and they were requisite, not that they had anything to do with applications), any math I will need for the rest of my life (trig, calc, Dirac notation, etc..), and a minor in physics. So, understanding what is happening from a mathematical perspective isn't something that would be beyond me. But, like I say. I have no idea WHAT is happening here.
I've never been a person to just "go with the flow". I have to know why.

Please help me.
Thanks for reading this.

 

[thermionic]

I suspect we all, even the most experienced members, get nervous when powering a new device up for the first time. Even if you're a DIY Ninja, there are always daft mistakes that anyone can make, particularly on larger projects where you have a lot of jacks etc to wire up. We've all been there...

A couple of tools you can't afford to be without would be a variac and some very low value test fuses.

The test fuses are absolutely essential and will ensure you don't blow up valuable parts such as mains transformers with multiple secondaries, or expensive chokes.

When powering up for the first time, it's a good idea to have a 'scope and multimeter watching the outputs. Wind up the variac gently (on solid-state projects, a Bench Supply is essential - most will have a pot that lets you wind up the volts gradually - you can DIY a bench PSU, although you can get OEM units quite cheaply on Ebay) and watch the 'scope for anything that looks too funky and - most importantly - look at your voltmeter for signs of DC.

I keep my 'scope, meter and bench PSU next to each other. As I raise the voltage on the supply or Variac, I watch 'scope and meter like a hawk.

The only way to learn is from experience. Make sure you have a lot of patience - learning the hard way on the bench, i.e. empirically, is the hardest way, but the best long-term.


Justin

 

[NewYorkDave]

A lightbulb-based current limiter is a must-have.

I've been building stuff for many years but I still power up new equipment for the first time through the current limiter, no matter how I've double- and triple-checked everything.

It took a long time for me to get to the point where most of my builds work right the first time--but experience just makes the errors less frequent, it doesn't eliminate them. Always take the necessary precautions to protect yourself and (less importantly) the equipment.

As far as education, there are great resources out there for learning theory (Howowitz and Hill's The Art of Electronics should be in your collection). But when it comes to the finer points of building things, there's no substitute for learning by doing.

If you can hook up with a more experienced hobbyist in your town and spend some time with him in his shop, you're ahead of the game. Amateur radio provided a great way for younger hobbyists to learn from the old hands, but not many younger people seem interested in it anymore. (There's too many sleeker, sexier high-tech distractions in the early 21st century).

 

[bcarso]

Turning the switch on for the first time still gives me anxiety, and I have been at this now for about 40 years of getting paid for it!

I often bring circuits up in sections but you do have to know what you're doing. A high voltage power supply may not like having no load, for example.

As far as learning more, and since you are not intimidated by physics and maths, alongside Horowitz & Hill I recommend Peter Carroll Dunn's Gateways Into Electronics, ISBN 0-471-25448-7. It's a gem.

 

[Svart]

for 10 years now I've always powered things on from a distance, with eyes closed, usually shielded by something.. :green:


It's fun to make small stuff explode but after a while it gets expensive.. then you move to higher power equipment and it REALLY starts to get dangerous.

 

[PRR]

> I know I could hurt myself very badly

Oh, geez. It isn't THAT dangerous.

We just say that to newbies, because we DON'T want some idiot getting hurt and blaming us.

I just put a meter on the main B+, stand at the far end of the power cord, and plug it in.

Last year I saw my "400V" power rail rising 300, 400, 500, 600.... and pulled the plug before anything blew. (Some idiot {me} re-wired the rectifier wrong.)

The year before,on a 10-Watt supply, I plugged in, the room lights dimmed. I didn't think a 10-Watt toy should do that..... YANK! Same idiot got the 120V and 12V sides wrong.

And I have stood by while a "115V" power amp was getting 170V (not my fault this time). BOOM! Mushroom cloud! What a stink. Cleared the room.

Unlike mistakes in cars and lawnmowers, audio electronics rarely maims anybody.

I have, on occasion, fired-up with a 60W lamp in series with the victim. If things went right, the amp powers-up to sub-standard voltage and works poorly; if things go very wrong, the lamp lights up bright and nothing burns. Likewise I like to flame-test audio POWer amps with 10 ohm 10W resistors where the 0.22 ones will go. If the bias is set "right", it comes up a little starved and unable to put big power in a speaker. If things are wrong, the 10W resistors smell bad and get toasty, nothing else (usually) burns.

Shock is an issue. Don't touch any metal until you check for zero volts from chassis to wall-ground. If I have reason to doubt the insulation, and can't do proper bench-checks, I get one hand between chassis and other audio and wall grounding. A 120V shock from hand to foot or leg or other-hand to concrete or water-pipe is nasty dangerous. A 120V shock from one finger to another on the same hand stings but doesn't kill. Most serious harm on 120VAC comes with fairly damp large-area contact: lying on ground, or under fast-food machinery. Dry wood floor, dry rubber shoes, wood bench, your main risk is "two hands" (a shock through the chest", hence the "one hand in pocket" rule.

 

[josh]

If it isnt going to be any worse than the time I unplugged my distributor cap while the car was running and the arc went right up my arm and knocked me down.... or the time I was learning to TIG aluminum and struck an arc far enough away from the workpiece that the arc went backwards into my hand...

then shame on you guys for scaring me.

 

[Svart]

That distributor shock is high voltage, around 10kv or so but very low current. not really enough to do much besides act like a stun gun.

Now, that TIG is MUCH different. That could kill you for sure.

 

[josh]

Thought I'd post a site I found with dozens of books in pdf format on circuit theory and design.

http://www.pmillett.com/index.html

older stuff, but still very relevant

 

[The Kid]

Thought I'd post a site I found with dozens of books in pdf format on circuit theory and design.

http://www.pmillett.com/index.html

older stuff, but still very relevant

Somebody beat ya to it last year:


http://www.groupdiy.com/index.php?topic=14281&start=0&postdays=0&postorder=asc&highlight=technical+books+online&sid=34f25c766441ca49dfad280908c21f43

Where can I learn about this? Online, not online, I don't care. Throw it at me please.

Start with the meta's, and don't be afraid to search. :wink: :sam: