power

[MoltenVoltage]

Wow, this is the closest thing to an intervention I have ever seen on a forum.

Good job guys.  Hopefully dude will quit before he hurts himself or someone else.

I got a cheap lesson when I first started modding things, I changed the jack on the back of an amp to be a power switch, switchable with a footswitch - just hacked the power cable and spliced it on in.  Then one day my three-year old was about to plug a guitar cable in the jack and I realized what a f*ing idiot move I had made.

I'm embarrassed to say it also took me a few close calls with burning balls of solder on my face before I started wearing eye protection religiously.

[doc_drop]

I've been terrified of HV since I was a 15 year old kid building ham radio kits. Yes, I have been lifted off my feet by accidentally discharging a cappy, with my finger. Not fun, hurt like hell, and I'm very happy to be alive at the wise old age 0f 48!

But, I would do a HV project again. But, my level of care would go up 400% from 9v circuit work. That HV stuff does not have much wiggle room for mistakes.

[JKowalski]

I got a cheap lesson when I first started modding things, I changed the jack on the back of an amp to be a power switch, switchable with a footswitch - just hacked the power cable and spliced it on in.  Then one day my three-year old was about to plug a guitar cable in the jack and I realized what a f*ing idiot move I had made.

Wow. Just wow. 

I might have to agree with you, that was a pretty bad call there.




I don't know about everyone else - but I'm not trying to tell him to quit outright! What kind of help is that?

I just want you to precursor your trial with a healthy dose of knowledge - that you MAKE SURE you know exactly what you are doing, and that you follow all the precautions.

[kingdomamps]

I've had the good fortune to build lots of different devices, many of which contained dangerous voltages.  One of my first line powered projects was an original light switch timer that I made for a 6th grade project (Dad was helping).  I vividly remember the sense of trepidation as I tightened down the barrier strip terminals and got ready to apply power.  In some ways, it still happens every time I apply power to a new design.  Maybe you guys can relate, but I keep my finger on the mains (or variac) switch, I'm listening, looking, smelling,  and as soon as it seems like the coast is clear I start taking the vitals of the thing like some sort of ER doctor, measuring voltages and taking temperatures.  It's all a pretty tense affair.  No matter how confident I am in my design and application skills, I can't imagine that feeling ever going away.  Maybe that's odd, but if I lose my healthy/fear respect for plate voltages, the cost of components, and my own personal safety, then I'm alot closer to a serious accident.  I feel fortunate to be able to build stuff and try to address the process with as much humility as I can muster.

All the best,
-barry.

[MikeH]

And that's the way you should approach it.  "What could possibly go wrong?" is at the other end of that spectrum.

It had my first experience with HV at the age of 9 or so, when I was plugging in Christmas lights and the plug casing came apart in my hand.  I'm lucky I was laying down rather than standing up.  It was pretty exciting, and my forearm felt a little odd the rest of the day.

[kingdomamps]

And that's the way you should approach it.  "What could possibly go wrong?" is at the other end of that spectrum.

It had my first experience with HV at the age of 9 or so, when I was plugging in Christmas lights and the plug casing came apart in my hand.  I'm lucky I was laying down rather than standing up.  It was pretty exciting, and my forearm felt a little odd the rest of the day.

Funny, as I design, troubleshoot, and power up new stuff, I'm always thinking "What could possibly go wrong?", but the connotation is a little different.

When I was too young to be doing such things, I was trying to get a UPS working for my lightning fast 286.  I thought it was cool, but it really was two or three generations old by the time I got it in elementary school.  I opened it up, got bit by the AC on the fuseholder, (why would I unplug it?!? ), closed it up and never touched it again.  If the power had gone out, I could have lost dozens of batch files, Qbasic programs, and a shareware install of Wolfenstein 3D.  It would have been a tragedy!

[Lurco]

continued: Working with AC for the first time - help me not to die. 

[petemoore]

  1rst: Understand that you could die playing around with it.
  2nd: Don't mess around with it unless you and those you are related to are all prepared for that event.
  3rd: {Goes at the top} for best results and greatest safety, understand the electricity we work with completely, sometimes simply knowing to leave it alone is enough.
  4th: Just knowing where the dangers are and how to eliminate them is enough, know and follow the rules, if you want to improve your chances for greater longevity.
  Leaving the dangerous stuff to those how have complete setup and knowledge for working it is strongly recommended as the safest route of all...say...using things that came with a warranty.

[thereverend]

dishwashing gloves and saran wrap as an insulator? wtf?

this isnt gonna end well.

[GibsonGM]

Anyone 'playing' with mains should definitely have some background!!  I got mine by working as a maintenance guy.  I had a 50 yr old experienced guy as my 'supervisor', and he showed me how to wire in outlets, lights, etc.  Told me those little things you don't read about when you're 22, such as "switches go in the hot line - BUT, sometimes some muck has wired it into the neutral, and the fixture might still be hot"!!   Not everything goes by the book, and if you or someone else has made an error in the past on a project, you can get killed by becoming complacent.  One time, every indication showed a circuit was off at the breaker, but he got zapped anyway (probably a crossed neutral/hot somewhere, combined with a miswired breaker).  No DMMs on that job, and maybe no ground in the old house to test against, either.  THAT was a lesson and 1/2! Petemoore's 'complete setup' wasn't there.   I've been shocked by water pipes that have current on them due to a miswire, too.  Can't count on the work others have done, gotta check yourself and know how to do so properly!
   
Like above, I always feel like I'm working with nuclear material when I power up an amp with HV, and treat it as if it was about to jump up and bite me (and it COULD, if a cord got yanked or something).  It's the unexpected, dumb things that get you (like forgetting to shut it off and PULL THE PLUG before discharging caps, etc).  The thing you've done 100 times, and forget to do the 101st because you're too comfy.

It takes many baby steps, and much time, to gain a real appreciation of how to work on larger amps safely.  And a great willingness to listen to, and evaluate, opinions of those who know more - and who may NOT know more but act like they do.  As well as a mad-scientist-like anal compulsion to check, re-check and check AGAIN that potentially deadly scenarios have been dealt with BEFORE doing that simple little mod....and trust me, it's hard to stay that focused when you want to get something done in a hurry.
It just takes time, reading, developing good habits, good planning, working with others who have experience, and starting small.
 
Jumping unprepared into the unknown when dealing with HV is a recipe for a quick trip to a casket or worse, becoming a semi-vegetable with brain damage.  If the opinions stated by knowledgeable people in this topic aren't enough to make one learn the right way, then they're an idjit!   

[El Heisenberg]

i said shrink wrap as an insulator not saran wrap! And the rubber gloves were a joke! Read all the posts before you makr a comment!

[frank_p]

Just to illustrate the hell I lived :

I once had a serious electric shock on the AC 120V and let me tell you it really ain't funny when that thing bites you correctly.  It was the last thing I expected.  First, the moment you realise you made a serious error is the moment when you really worry if your life is going to end.  I got paralysed on the main voltage and I don't remember for how long.  All the muscles of my body were completely frozen.  Could not move or yell to call help: all that was left was my anticipation and that feeling of being completely trapped.   All I saw was orange and black alternating at 60 Hz.  It stopped because the flesh got calcined and dry. What is wonderfull about the AC line is that it messes up with your nerves so well, that I did not feel I was totally roasting. It stopped.  When I looked at myself, all I could see was a black spot. Then I really got scared (but the damage was already done). The next thing was going at the hospital (and you still don't know how bad it is).  They covered me with special creams for days.  A few months later I had to go to the hospital and be in total anaesthesia to open me, extract the flesh that was burned in me and sew me back. I got back home.  Then, I had to wait more than a year so the surgeons could reopen with a scalpel, the flesh that had been "soldered" together.  If it had not be for the calcined flesh, I would perhaps have died there.  Happily I just had some fear, a self BBQ and scar.

With a death capacitor you might not even have all that trouble (and all the littles troubles that life can bring).  Might not even have the time to realise what happened.

Why increase significantly the probability that something like this happen to you ?  Trained (and certified) person can supervise you at first to see if your method is correct.  If only someone could really feel the power that is actually in the line (when it goes right under the epidermis) before playing with it.      This experience is why I am still building stompboxes and I had not builded a tube amp, even if it was my first desire.

[GibsonGM]

Listen, El...nobody is saying you're an idjit, I meant you're an idjit if you just dive in.  It sounds like you really want the info, which is GOOD, as long as you learn through the right steps before proceeding.  Look at Frank's post above (sorry 'bout that, Frank, that really sucks!!  I got hit by a huge filter cap inside a trash compactor - that I NEVER thought I would be able to make contact with, but I did...happier ending than your story, but scary! Speedy recovery).

Did you know that materials have a dielectric breakdown, El?  Those dishwashing gloves aren't meant to handle power being applied across their surface.  At some voltage level, they do no good.  They're not lineman's gloves, tested for kV levels - they could melt, rapidly, exposing you to contact with a live component.  Or just make you so clumsy you cause an error just by having them on!  And heatshrink tubing is great stuff, but sometimes a thread of wire is still exposed...and makes no difference if you get a hot chassis.

R.G. suggested getting ARRL handbooks - the library carries them, usually. That's where I got some real knowledge about AC power.  I'd find one of those, a basic electronics course book, and search the net for "electronics tutorial".  Even "wire an outlet" stuff.  You really gotta understand how power flows before you get into higher-level AC stuff.   Like, when is a ground not a ground?  At what point can DC flow through a capacitor?  What happens when I exceed a power transistor's ratings and it fails, with 300V on it?   Not only do you have to plan something right the 1st time, you have to anticipate FAILURES of those parts, and what effect that could have on your (or someone else's) body.  Transformers can exceed their ratings even though on the secondary you're not drawing all that much current - these are things you need to know before you start 'doing'. 

Doing experiments with a step-down transformer (say, 120V to 9V, rectifying, filtering, and regulating that to 5V....Radio Shack has power supply books to get into this) can be a good place to start ONCE you've got the idea.  That implies you already have a strong knowledge of low-power DC, though.  Like, Ohm's Law backwards and forwards, and being able to do power calculations well.  The wattage figures change rapidly as you work with higher voltages, and can make parts break down quickly with rather small changes in component values...

Just do some reading, taking the time to learn all this is what makes it fun, really.  Then small steps.  I wanted to tackle big stuff fast when I was getting into electronics - DC 9V seemed so LOW POWER, lol.  But now, 95% of stuff I do is 9v, less than 100mA; doesn't  take a lot to achieve some nice results.  And you learn how things fail that way, with no danger ;o)