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Any one intersted in Microwave Oven Transformer's needs to watch this!!

ElectronTubesRule

Active Member
Sep 6, 2011
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I think this demonstrates just how robust they can be especially with low voltage high amperage. The fun part is near the end when you see what he doing with them. Kind of makes 30 seconds to 2 minute key down seem like kids stuff from an abuse and durability perspective.

This is just proves my idea of using one at low voltage on the secondary as fil transformer. You easily use one to produce the voltage and current needed by the High Power Russian tubes like the Gs 35b I think it is and other.

If he knew how to put together carbon rods he could smelt metals with that or as is he could easily use it for heat treating and many other useful things instead of destroying tools but boys will be boys!

DIY - High Amp - MOT Power Supply - 3000Amps at 2 Volts - YouTube

I doubt his claim though of 3000amps not volts volts are under 3 on this kids project. He claimed that his amp meter was destroyed when he fired it up that I can believe. It almost reminded me of induction heating of axles back whrn GM still made their own axles in house. They would get the same glow and the sound was very similar.....I always felt bad for the guys that worked near the induction hardening machine I can not imagine being that close to powerful electrical field did them any favors!

Any ways I thought I would post this as an idea of what can be done with MOT. I find that one totally by accident.
 

Well I said "GS 35 I think?" meaning I amnot sure if that is the tube number I am looking for....THeir is one that needs some insane amperage like 20amps+++.........I am really not feeling like digging through Russian tube spec.'s to find the right one.....I have two twins vomiting and running fever's so I have been stuck home caring for them not making money and not getting much sleep. So I am kind of lazy and run down at the moment.

As to Junk what makes a MOT JUNK? If the Microwave was not junk in your kitchen then why would a single part from it be any more "Junk" then when it was a "hole unit". The MOT is usualy the last thing to fail in a MIcrowave. Funny how all the Amateur "SNOB's" see them as junk even though everything else on the microwave normally fails first. I am sure if we put Peter Dahls name on one it would instantly be world class!!!LOL

Here goes a novel idea for you! Americans produce an insanely high amount of waste and much of the stuff in land fills could have been reused or reclaimed. If I have 2 MOT's already and I got them for free and they will do the job of a $20 transformer then I have just saved $20. I have kept a useful commodity steel and copper from being tossed in a land fill. I think the fact that I can build a steel smelter or a stick welder or a filament transformer from a used up no longer good microwave or two is the ultimate in recycling and being frugal. Having spent time with men that lived through the great depression I can tell you I have skills few man of 38 have. I can make seals from paper and leather, I can do body work in lead, I can forge parts and knives in my back yard, I have cast my own parts out of aluminum using store bought charcoal and two terracotta bots and a crucible I made myself. Most of the stuff I got out of the trash or recycled from my own work out things. If you have$20 to spare then their is no harm in buying what you need. What do you do when you either do not have the money or the parts you need can not be bought???? I spent some time in Eastern Europe and in Africa and I can tell you that people that are used to buying everything they need tend not to get very far and are of little use to themselves or to other's and they have little to offer in trade or for work! I once peened an axle crack shut they used oxy/act torch and a stick welder to weld up the area.....Cast iron is hard to get a good weld. I rebuilt the rear end and had to use to use grease and the pattern it made on the gear face to set it up because I did not have the proper gauges to it as I normally would luckily for me my Mentor was a young machinist during WWII and figured I should be able to do anything I could do in the shop in the field under combat conditions. I am forever grateful to him for teaching me how to do with out the creature comforts. The ability to make what you need from what is at hand be it machine parts, tools, chemicals, electronics, medical tools or devices is incredibly liberating. Why? That I am also glad I went through Ranger Training. Why??? I know that no matter what I do or where I am I can adapt to any situation and over come any odd's. I am never at the mercy of what I can by or what other's will sell me.

Plus while I am not one to ram Nuclear Subs with a rubber dingy and I do not take to people tossing blood on women wearing fur's I do like to do what I can for the environment and being frugal and re-appropriating materials that are still good but not needed for new projects is a fantastic way to keep this world beautiful! Plus I dare say that for anything under 50 volts I would bet that a reworked MOT is better then the dedicated filament transformer. Keep in mind that the center tap and rectifier concern is really only a minor issue and only if you need DC if you can use ac it is not a problem at all.

When was the last time you looked at a MOT? Have you even handled one or ever used one? If you have not used one then what is your opinion based on? I will guess it is based on the opinion of other's that like wise have not actually used one. Their is a legal limit unit using 2 MOT in Australia.


Not all amateurs care about saturation either. More then one well known HomeBrew guy has suggested that one should pick a fulfillment transformer that saturates at the current limit you want so that no current limiting is needed. The first time I read that it made my head spin but it does make sense on filament transformer's. The nut operating the unit is in charge of setting it up so that the transformers are not saturated. I already know I am going to build a HV supply down the road with 4 MOT's. I will buy the MOT's new and will gladly challenge anyone to build a better power supply paying full retail price for their transformers and parts. At $11-$20 each new I am sure you can not buy anything with Peter Dahl new for $44-$80 in the 4000V 1amp ball park. I guarantee the extra capacitors and diodes I will need to clean things up will not even increase the cost of the build enough to make any impact in the end cost!!!

I will be licensed long before then so maybe I can get some real testing done and an article written on the subject. Seeing how 2500V @ .800 amps from Peter Dahl would have set me back $480 and for the same voltage at 1.5 amp's $580 I am confident I can spend far less and get a product that will work more then well enough and that no one will ever hear a difference over the air. So if I can build an entire power supply for less then $480 that works perfectly then I win. I already know I can do that.

I know it will not matter what the ociliscope says or the digital spectrum analyzer their will always be people that will look down upon it but I could care less! The people that will look down upon it no matter what are not people who's opinions matter to me. These are the same people that made fun of Heathkits amplifiers with their little tiny transformer's, voltage doubler's and fans powered by refrigerator evap motor and phonograph motor's. It is funny how no one sells amplifier's with 76lbs. transformer's in them anymore they all have doubler boards and smaller transformer's so I would say that the world decided all those nay sayers where wrong.

Oh and for the record never assume I am using a nasty voice or intend to mean.I know that because I do not do written communication 1/20th as well as I publicly speak that I can come off as being terse. So for those that are not my intended audience know that I have no ill will towards you and am not speaking harshly......I am trully the Gentle Giant it takes a lot to even make me raise my voice let alone use an ill mannered tone.
 
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mot power supply

hi folks,
on the topic of mot's as plate transformers, i have two 1000watt mot's in parellel, 12- 650mfd/450vdc computer grade caps with 200k swamping resistors. it provides 2500 vdc,800ma to power my home brew 2 3-400z amp. produces 1kw with home brew 2 6km6 100 watt driver.has a voltage drop of 200vdc on transmit. have had no contacts say it sounded bad, just loud. did'nt have the funds for a plate transformer so i had to go to the junk box. they do work and are easy to wire up. did'nt worry about saturation as i could'nt do anything about it. did remove shunts and filiment windings from transformers. thanks ,just my two cents.
 
Before you go running for your MOT stash, you might want to hook one up to the line voltage for an hour with no load on it. Observe the higher then normal no load primary current and the associated core heating. Since the MOT never operates continuously, they are able to reduce costs by placing the bare minimum amount of windings on the core. This results in reduced inductance across the primary. That is what increases the no load current and heat.

You may ask why would they do this on the MOT? For every wrap you leave off of the primary, you can leave off about 15 or 20 turns on the secondary and still get the same voltage as long as the turns ratio is the same. You can save a lot of copper if you're willing to compromise the ability to keep the primary energized continuously. While this may not be the case with every MOT, it has been in all of the 15 or 20 I've experimented with.

There are several ways around this. You can remove the filament winding if you're only using it for HV. Then use that space to wrap another 30 or 40 turns of wire similar to the primary and add it in series. Use transformers with 220 primaries and only apply 110 volts. Both of these will also produce a lower secondary voltage. Use two matching transformers in series. Without doing any of this, most MOTs will experience a 20 degree increase in core temperature within one hour with no load applied. The problem gets exponentially worse as they are loaded to their limits. This is true even if the load is intermittent since the transformer never gets to cool down when no load is present.
 
mot's

hi shockwave,
all of the info you posted is correct, and i shoud have included it in my first post. using matching mot's is a big help as they have the same ratings. i have used mismatched mot's and they don't play well together, but they will provide hv output.

it is also a good idea to remove the hv winding from the core so the core is not at a hv potential. a deadly situation to say the least. this is when you find out how cheap the mot's are made. the ones i'm using now are from damaged kenmore units and they have copper clad alluminum wire.

i have a 14.4 10kva pole pig that i used on my 12" tesla coil. my thoughts are to run the two secondaries in series using the same shorted welder as ballast and a 115vac variac to adjust the voltage to achieve 3-3.5 kv output. think it will work? your input is greatly appreciated.

NOTE: i do not recommend anyone trying to duplicate anything i may post, as it is lethal high voltage. you have no second chance. if you need a plate transformer, buy the proper one that is rated for your needs.
 

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