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Registered Member #964
Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134
I just got an old microwave from freecycle. It had screws on it that apparently they don't make bits for anymore, but I got around that by tearing the sheetmetal.
I'm just looking for safety tips before I try and pull out the magnetron/MOT/MOC. I think I saw a 7.5k .1uF cap smaller than my thumb somewhere in there...
Should I be concerned w/ charge in the MOC? the terminals are kinda hard to get to for shorting out. anything else I should watch out for?
Woops forgot one other thing: What could I do with one MOT and one cap until I get more?
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Pull the plugs on the cap with a plier and shortcircuit it, that should be the only part inthere that can still maintain a lethal to lesser lethal shock.
I have had no problems with MOCs with the above procedure, just dismantle the MOC as the first if you want to be sure.
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
Personally I've never found any microwaves in which the main HV capacitor contained a charge. Most if not all have an internal or external bleeder resistor and the 2 joules stored in it is not likely to be lethal unless you manage to stab yourself directly in the chest with it (in which case you probably shouldn't be allowed to even have access to a microwave or the internet).
As for the MOT - draw arcs with it? You don't need to have a resonant setup to have big arcs. Depending on the size of the xfmr and your breaker situation, you may not even need a ballast.
You could also shop off the secondary and rewind it for a high power, lower voltage power supply.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Billybobjoe wrote ...
Personally I've never found any microwaves in which the main HV capacitor contained a charge. Most if not all have an internal or external bleeder resistor and the 2 joules stored in it is not likely to be lethal unless you manage to stab yourself directly in the chest with it (in which case you probably shouldn't be allowed to even have access to a microwave or the internet).
As for the MOT - draw arcs with it? You don't need to have a resonant setup to have big arcs. Depending on the size of the xfmr and your breaker situation, you may not even need a ballast.
You could also shop off the secondary and rewind it for a high power, lower voltage power supply.
Regardless if the capacitors have an internal or external bleed resistor, you should always check to make sure high voltage capacitors are discharged period. If you don't do this, than you shouldn't be allowed to have access to anything high voltage. Never assume something is safe - always test. Those few extra seconds could save your life.
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
Dr. Shock wrote ...
Billybobjoe wrote ...
Personally I've never found any microwaves in which the main HV capacitor contained a charge. Most if not all have an internal or external bleeder resistor and the 2 joules stored in it is not likely to be lethal unless you manage to stab yourself directly in the chest with it (in which case you probably shouldn't be allowed to even have access to a microwave or the internet).
As for the MOT - draw arcs with it? You don't need to have a resonant setup to have big arcs. Depending on the size of the xfmr and your breaker situation, you may not even need a ballast.
You could also shop off the secondary and rewind it for a high power, lower voltage power supply.
Regardless if the capacitors have an internal or external bleed resistor, you should always check to make sure high voltage capacitors are discharged period. If you don't do this, than you shouldn't be allowed to have access to anything high voltage. Never assume something is safe - always test. Those few extra seconds could save your life.
I do check MO caps for a charge anyway, I was simply making a point that if you can't immediately because of the orientation then don't piss yourself over it. Check it when you remove enough components to make it possible. There's no need to be dramatic. Lets not even get into "those few extra seconds could save your life".
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
People: let's make peace here. Please don't be cross with one another for issues concerning safety because written communications has no verbal inflections in it, it;s tough to get the totality of what someone may really be getting at....Let me explain....
I used to work in a situation where I would take the firearms of those who came into a building and lock them in a locker. I was totally in the habit of opening the action (depending upon the design) and pulling the magazine or emptying the cylinder of cartridges, counting them, putting them in a property envelope, leaving the action open and locking both away. So that locked up was a weapon that was empty. The chamber was empty as was the entire weapon.
I got so that even though I knew what I was dealing with was lethal, I was working with concentration, confidence, & some real measure of speed.
When another person took over, they had a different style. He looked over the weapon, worked the action and poked a finger into the chamber, etc. He was quite competent; but the had a different style of checking.
Even though I wanted to tell him that if you could see the floor through the barrel the thing was empty, I let him have his process as the important issue was safety & he was great at that little chore. The result was the same: an empty weapon, triple checked & locked.
My point here is that we ARE talking about something that can be lethal & safety never hurts nor is it a put-down to be reminded of that.
While enjoying this hobby I find myself more comfortable with NST's more than MOT's due to the false belief that one is LESS lethal than the other. If I was really on top of my game and my safety practices were continual, my comfort level would be similar in both instances. I remind myself of that & this issue actually has helped me to see that if safety is a priority then HV is HV albeit there are some utilitarian differences in where and when you'd work with them.
Just as I wouldn't fire a .50bmg in a little indoor range, you might not elect to fire up a pole transformer in one's kitchen.... Safety is always a good thing. Let's not let misinterpretation spoil the positive nature of that issue.
Back to topic: Does any have experience with the various altered winding for MOT's? What are some of the possibilities that have been successful?
Registered Member #964
Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134
I think I'll go for arc drawing, don't want to waste that nice shiny secondary =)
Yep, this cap has a bleeder resistor in it. not sure the value though.
Should I go buy some cheap welder's goggles for eye protection when arc drawing? or something else? also: What do you recommend in terms of a ballast? I have no idea what my breakers are rated for, and atm feel too lazy to check.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Spedy wrote ...
I think I'll go for arc drawing, don't want to waste that nice shiny secondary =)
Yep, this cap has a bleeder resistor in it. not sure the value though.
Should I go buy some cheap welder's goggles for eye protection when arc drawing? or something else? also: What do you recommend in terms of a ballast? I have no idea what my breakers are rated for, and atm feel too lazy to check.
For simple ballast, you can use two parallel microwave caps in series with your arc, the effect of resonance will also make your arcs 2x-3x bigger (see my avatar that is an arc from 2 MOTs).
Else you can use anything that has a high power resistive element in it (oven, heater, iron etc.) eventually you can parallel more of these. Shoted welder works too for an inductive ballast.
For eye protection, sunglasses are absolutely enough (actually it will not hurt your eyes if you look at the arc directly but prolonged exposure to UV from the arc can get you "sand" in your eyes)
Registered Member #964
Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134
Hmm, I think I remember reading somewhere about home-made inductive ballasts, big rolls of wire w/ sliding iron cores to adjust them. If not that I also remember reading about a cheap water resistor based around a small garbage can and some copper pipe.
Which would be better, resistive/inductive? should I worry too much about the power factor?
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Extracting parts from a Microwave
