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isw <isw@witzend.com>: Feb 12 09:59PM -0800 I recently came across a YouTube video where a guy rewound a microwave transformer to make a spot welder.   In talking about it, he stated -- and repeated -- that it was very important for the secondary winding to have the same "sense" as the primary -- that is, both windings had to go around the core in the same direction.   I know that matters if the transformer is handling very asymmetric waveforms such as in a flyback configuration, but I have never heard that it matters for plain old 60 Hz. sinusoids.   Does it? Or was the guy just confused?   Isaac

Phil Allison <pallison49@gmail.com>: Feb 12 10:30PM -0800 isw wrote:   > waveforms such as in a flyback configuration, but I have never heard > that it matters for plain old 60 Hz. sinusoids.   > Does it? Or was the guy just confused?   ** A spot welding transformer is almost the direct opposite of a microwave oven tranny - big step-down instead of step-up and the lowest possible leakage reactance instead of heaps.   To help with the latter, it could easily be important to wind with the same sense. Also winding multiple, identical secondaries and connecting them in parallel is the way to go plus using other techniques like interleaving and use of strip conductors for the secondary.   Getting 3V at 200Amps is non trivial.     ... Phil

N_Cook <diverse@tcp.co.uk>: Feb 13 07:59AM On 13/02/2015 05:59, isw wrote: > that it matters for plain old 60 Hz. sinusoids.   > Does it? Or was the guy just confused?   > Isaac   Even using it in reverse, swapping primary and secondary, you will not get the low volts and high amps for welding. Did u-tubber just use the core and existing primary and rewind the secondary secondary with 1 to 2mm diameter wire? should be obvious in the vide, those sorts of dimensions

"Miguel Giménez" <me@privacy.net>: Feb 13 01:31PM +0100 El 13/02/2015 a las 6:59, isw escribió: > that it matters for plain old 60 Hz. sinusoids.   > Does it? Or was the guy just confused?   > Isaac   May be he is winding an autotransformer, although it's not very safe for welding :) .   -- Saludos Miguel Giménez

spamtrap1888@gmail.com: Feb 12 10:44PM -0800 On Saturday, February 7, 2015 at 12:19:48 AM UTC-8, Scotophor wrote: > > has dropped by 50%. Selection of encapsulant can either accelerate or > > retard this effect.   > Really? Then why do the online references seem to want to refer to dark current only in terms of photodiodes and other light-detecting (rather than emitting) components? I.E., dark current is the leakage current which flows when a light detector is detecting no light. Sure, an LED /can/ be used as a light detector, but for typical usage, the standard definition of dark current seems to be irrelevant. Can you cite references for your definition of "dark current"?   Fine. "Nonradiative." Only takes three times the keystrokes.   > > > Statistically speaking, I find it hard to believe that: upon identifying the LEDs, (A) I already had two of them, unused, among my supplies, (B) I already knew someone whom I believed might also have some, which I was able to verify in minutes by browsing his website. I later obtained more than a dozen of them from him, a mix of unused examples and pulls. (C) Within days I had found another person online who sent me three more, yet (D) In the 6+ months since, I have not been able to locate even a single additional example. What are the odds that I could locate and acquire the world's entire available supply of these in such a short time, and that I already knew the person who had most of them? It boggles my mind to think that I found as many as I did so quickly, yet there now don't appear to be any more to be had, anywhere. I believe there must be more out there; it's just going to take more time and effort to discover them.   > > Sooner or later, crap tends to get flushed.   > Are you making assumptions again, or do you have personal experience with the LEDs I'm seeking? Also, I can direct you to several collectors and sellers of some of the earliest commercially-made LEDs, which are IMO far more suited to be labeled as "crap", based purely upon light output and longevity, than those of my current quest. If people collect that junk, then why not some that are brighter and more unusual?   Crap is stuff that appears only in blisterpacks, and then gets surplused. Not like having some, say, Monsanto LEDs.

jurb6006@gmail.com: Feb 12 12:34PM -0800 I don't get quite where you're coming from here, I'm sure it is off topic but since we're here...   Safety is an anaethma to me. I think seat belts and air bags in cars should be illegal. Instead put big spikes in the dash on the driver's side so that if the stupid fuck doesn't watch where he's going and hits something he gets impaled. This will cure the assholes who think proper following distance is one inch per hundred miles per hour. Of course the doors are reinforced with I beams and sbit so if you get Tboned you're alright.   Guards on saws. First of all, a guard on a table saw is the worst goddam thing ever. Second of all, if you are so clumsy or infirm that you might fall on that blade or stupid enough to stick your hand on it, should you REALLY be doing carpentry ?   Even worse are those saws with the electronic brake that stops the blade in microseconds if your hand touches it. Now what happens when someone gets used to one of those and then later has to use a saw without that "feature". That "feature" might make them stupid enough to cut their hand off on a normal saw. What's more, electronics do break down, no question. Otherwise this newsgroup would not be here. So if that little sensor or solenoid stops working and someone cuts their hand off on a saw YOU guaranteed would NOT cut their hand off, guess who gets a bunch of money.   That's right, the lawyers.   Then you get a structured setlement from a class action lawsuit, and then sell that settlement to J G Wentworth for half its value and in the end, the culpable party never paid a dime. You just borrowed the interest on it. The stupidity of all this shitis overwhelming, really. In the only country to put a Man on the moon. Really, the only country to produce an extraterrestrial, albeit for a short time. But hey, even ET eventually went home right ? (never saw it)   I used to be one of the best TV techs, and I can tell you that in the nbame of safety there is more shit in there that stops it from working than makes it work ! Reality is it makes it alot harder to troubleshoot sometimes. Increases repair costs, which is good for the manufacturer. In the old days, when the TV didn't have a good picture and was billowing smoke we would generally turn it off and call the TV Man. (well, we used to fix all of our own stuff, seriously) But that was common sense. People watched the TV. They watched their show, or there was a movie on that they found out about from the PAPER TV guide. Starts at eight, we'll turn the TV on at about 7:30 and let it get goood and warmed up. Then when the credits roll at the end we turn it off. We don't lock all the kids in a room with fucking Sponge Bob all day. That breeds more idiots.   We used to spend time with kids. Kids cannot learn from other kids, they must learn from adults.   And that is the fucvking problem, literally. Fucing makes kids, and the wrong people are fucking. the useless biomass is reproducing alot faster than us useful Men and Women. The useless are fucking up this world and I am all for not saving them from their fate anymore. Let Darwin's theory prevail, really.   Come on, if you but an RV ith cruise control there is a sticker that says "When using the cruise control you must still steer the vehicle" because someone took it as they could set the cruise control and go in the back, and probaably fuck to make another piece of biomass that should have been recycled before it was born for all the good it would do the human race.   Doesn't anyone think of contributing to human knowledge ? To the betterment of the human condition ? Even the betterment of humanity at all ?   I think we need to either start steriliing people or putting them in chastity belts or something. Well thre Norplany might be workable. God damn, we got seven BILLION people. Tha tis too much. Our food is from overproduced land and is thus has its mineral content diluted and that is causing a shitload of diseases. When are we going to learn ?   So basically, I support letting Bubba die when he says "Hey y'all watch this". I support things being unsafe. Use the dead as an example to the young so aybe they get smart. If not, off with their hand or heads or whatever. Consequenses teach the best, so without consequenses, what happens ?   Now mind you I am not tlaking out of a lack of experience here. I have been shot in the face, I have rolled a van all the way across a hole of a golf course, I have had my ass totally kicked by three dudes, I have had my head go through the windshield of a 197 Pontiac Grand Prix, but if I had been wearing a seat belt I would be in a wheechair now because the people in the back hit the seat moving it so far forward that I could not reach the door handle.   Safety my fucking ass, they make more money is more like it. just like a motorcycle, if my head hits the ground at 85 MPH, I would rsather be dead. Done with it.

spamtrap1888@gmail.com: Feb 12 08:58PM -0800 > Then you get a structured setlement from a class action lawsuit, and then sell that settlement to J G Wentworth for half its value and in the end, the culpable party never paid a dime. You just borrowed the interest on it.   The plaintiff could have gotten a lump sum settlement, but he CHOSE to receive money EVERY YEAR he was alive. Going to Wentworth means he gives up money that was supposed to make his life more comfortable.   Most jurors are cynical, and are not about to give injured people a windfall for no reason, by the way.     > We used to spend time with kids. Kids cannot learn from other kids, they must learn from adults.   I generally support that parents should spend more time with their kids. My parents had their own business, so they didn't have a normal 8-5. They prioritized putting food on our table and a roof over our heads.   And kids learn things from other kids that they cannot learn from adults. How to deal with assholes, or psychopaths, for example. Where their rights end and the other guy's begins. What their natural talents are, based on what their peers think of them. > So basically, I support letting Bubba die when he says "Hey y'all watch this". I support things being unsafe. Use the dead as an example to the young so aybe they get smart. If not, off with their hand or heads or whatever. Consequenses teach the best, so without consequenses, what happens ?   Consequences can be learned best when kids are on their own or with other kids, without parents to deflect consequences.

jurb6006@gmail.com: Feb 12 10:28PM -0800 Can't disagree much. Do you think schools are a good medium for this ? I have started to think that schools, at least government run schools are no good.   There is no way to do an A/B comparison, but the statistical evidence is whelming. Not quite overwhelming but quite solid to say the least.

Jeff Liebermann <jeffl@cruzio.com>: Feb 12 09:25AM -0800 >I've got another laptop needing a nVidia chip reflow. >I'm refining the technique. >What's the recommended air temperature?   Recommended by whom? Recommendations are all over the map. Here's mine.   Much depends on the type of solder used for the BGA chips. My guess(tm) is that most BGA's use solder balls which solder at 217C and starts to reflow at about 200C Meanwhile, the rest of the board is SnAgCu solder paste, which starts to melt at about 225C. These temps are from my measurements, not from the solder manufacturers charts and take into consideration my instrument inaccuracies. The trick is to target the oven temperature between these two temperatures so that the BGA balls reflow, but the components on the PCB are untouched.   Getting the temperature even across the board is a major problem. I've made measurements with an IR thermometer and thermocouple probes which convinced me that this was impossible. Therefore, protecting the PCB with an aluminum foil shield might be a good idea.   In the past, I would use my cheapo SMT rework hot air gun for reflowing BGA chips. It would work on the smaller BGA and flip chips, but fail miserably on the larger chips. I gave up using it for BGA repair.   Recently, I purchased a Black and Decker toaster oven at Kmart for about $25 to do some experiments. I reflowed some old PCB's to test the settings and thermal control. Things went well, so last week, I reflowed 14 HP JetDirect cards and 4 HP printer formatter cards. Some photos: <http://www.11junk.com/jeffl/pics/repair/BGA%20reflow/index.html> All 14 JetDirect cards worked, although it's too soon to determine if the fix is permanent. Only one of the formatter cards didn't work. Not a bad percentage for essentially an uncontrolled reflow.   During the above reflow test, I make quite a few changes to the temperature, timing, protection, etc. What I settled on is: 10 minutes preheat to 215C without the board in the oven. When I open the door and insert the board, the temperature drops quickly. I then reset the temperature dial to 190C and bake for 8 to 10 minutes. At the end I turned off the oven power, but did NOT open the oven door. When the temperature drops to about 100C, I open the door, leaving the boards still in the oven. About 3 minutes later, they are cold enough to touch and are removed.   Not the best temperature curve possible, but it works. What makes it work is that the thermal mass of the cheap junk oven is very small compared to a proper oven with insulation, firebrick, and a proper controller.   Much of my inspiration came from: <http://www.wayupnorth.ca/blog/2012/06/12/you-baked-what/> and various articles on: <http://www.FixYouOwnPrinter.com>   Notice that I did not protect the PCB with aluminum foil. I did that with some early board tests and found that it didn't do much except protect some electrolytic capacitor jackets. (I did remove the plastic front panels from the JetDirect cards). As long as the temperature was kept below where the solder paste on the PCB reflows, there were no problems. None of the other key factors seemed to be particularly critical. The bake time was varied from 5 minutes to 15 minutes. Anything over 7 minutes at 190C seemed to work.   Also notice that I didn't use flux. I'm fairly sure some really fluid flux would have helped, but I didn't have any handy and didn't have time to make some. When I previously tested the use of flux, I found that the alcohol base had evaporated long before the solder balls had begun to reflow. In other words, the flux didn't do anything. I did as well using just alcohol and no flux which just cleaned the BGA from accumulated dust and grease.   Several authors have suggested putting a weight on the BGA to help push the broken connections together. That proved to be a problem. The added thermal mass of the weight caused the heat distribution across the BGA chip to change, which probably resulting in good reflow around the edges of the BGA chip, and lousy reflow near the middle. At least that's my guess why a weight made things worse.   Whether all this will work for motherboards has yet to be determined. I'm not even sure they'll fit in my toaster oven. I have about 5 candidate laptops waiting, but the PCB's are still in the laptops. It will take time to extract and retest them. Probably next month.   Good luck.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

mike <ham789@netzero.net>: Feb 12 03:51PM -0800 On 2/12/2015 9:25 AM, Jeff Liebermann wrote: > take into consideration my instrument inaccuracies. The trick is to > target the oven temperature between these two temperatures so that the > BGA balls reflow, but the components on the PCB are untouched.   I suspected that one should use the lead-free profiles. ??? > work is that the thermal mass of the cheap junk oven is very small > compared to a proper oven with insulation, firebrick, and a proper > controller.   I've been afraid to put a whole motherboard in a toaster oven, assuming I could find one big enough. There's lots of plastic stuff/connectors etc on the board. Most toaster ovens have exposed elements. You get lots of infrared and a variable amount of convection heating. That scares me too. Thought about putting reflective foil everywhere but the chip and count on the IR to do it. But it's completely uncontrolled.     > candidate laptops waiting, but the PCB's are still in the laptops. It > will take time to extract and retest them. Probably next month.   > Good luck.   My current tooling consists of a bottom heater made from an old TIVO case. I cut a 2"x2" hole in the top for the BGA chip area to sit on and drilled a hole in the side for a power-controlled heat gun. Welded some baffles inside to guide the air from the heat gun to the square hole.   I sit the board over the hole with thermocouples on the underside and touching the BGA on the top. Aluminum foil protects the part of the top that's not the BGA. Flux applied.   Top gets heated with a commercial SMT rework heat gun with precise air temperature control. My air compressor is running wide open and I'm taking all the air flow I can get.   I know what package temperatures I want and have some idea from the thermocouples.   What I don't know is what air temperature I should be using from the heat guns.   Too low won't get it all hot enough. Too high will burn something.   I was hoping to avoid a bunch of experiments to determine it empirically. Would be nice to have a target temperature to start from.   This site is interesting: https://www.youtube.com/watch?v=c_Qt5CtUlqY   I hava a Maxtra 852D+ rework station. It's capable of 550W, but the air flow isn't high enough to keep the heater duty cycle high. I have very little actual experience with the unit. And my thermocouples read the air temperature 30C lower than the digital readout. Very small changes in position make radical differences in the measured temperatures.   I seek less ambiguity ;-)

Jeff Liebermann <jeffl@cruzio.com>: Feb 12 07:22PM -0800 >I suspected that one should use the lead-free profiles. ???   Yes, if the oven temp controller had the ability to follow a temperature profile. I'm not even trying to do that. Buy coincidence, just shoving in the board into a pre-heated oven, and letting it cool down seems to follow somewhat of a reasonable ramp, soak, and cool profile. However, that's pure luck, not intent. My point is that for reflow (i.e. repair) it does not seem to be that critical. Once I understood what was happening, I soon discovered what was the causing most of the reflow failures: - Too cold during soak. - Too short a soak time. Everyone was too worried about destroying parts by over heating, so they went for the lowest possible temperature and the shortest possible soak time. That's not going to work as I proved to myself by trying some of those recommendations. What I found was that I could soak for quite a long time as long as I didn't get close to the melting point of the solder paste used to solder the non-BGA parts. If I could keep the temperature at about 220C, I could leave the board in the oven nearly forever and it would come out ok. However, there is a problem. Because I didn't have a proper temperature controller, doing that would cause the temperature to slowly climb. The result is that the soak temperature is not constant but rather an increasing ramp. I can live with that as long as I target the end of the ramp at less than about 220C. If you want to do it right, go thee unto eBay and spend about $70 on a programmable oven controller.   >I've been afraid to put a whole motherboard in a toaster oven, assuming >I could find one big enough. There's lots of plastic stuff/connectors >etc on the board.   Presumably, you could find a sacrificial motherboard to test. Shove it into the oven at the highest expected temperature for a reasonable time and see what melts or burns. Thermoplastic parts will melt. Thermosetting plastic parts will not. You'll find most connectors made from thermosetting plastics because the original motherboards are soldered in a IR oven, which uniformly heats everything to the same temperature. However, if you want to be sure, LOOSLY wrap the connectors in aluminum foil. You want some air gap between the foil and the connector so that air acts as an insulator.   >Most toaster ovens have exposed elements.   Really? It thought the UL banned that in the 1950's. My Black & Decker has two glass tubes with heating elements inside.   >You get lots of infrared and >a variable amount of convection heating.   I think you'll find that it's almost all IR with a tiny amount of red in the visible spectrum from the red glow. Convection implied air flow. Unless you buy a convection oven, the IR (heat) is very unequally distributed around the oven. I proved that to myself when I ran my thermocouple probe around the oven to see how bad it was. My guess(tm) is about 40C from the hottest near the center to the coldest near the lower corners.   >That scares me too.   Note my domain name: LearnByDestroying.com You haven't learned anything until you've destroyed it and then had to make it work.   >Thought about >putting reflective foil everywhere but the chip and count on the IR to >do it. But it's completely uncontrolled.   Yep, but as I found, it works well without the proper controls. Sure, I would like an overpriced oven with the proper profiles, but lacking the financial justification, I used what I had and it worked. Foil works if leave an air gap.   >case. I cut a 2"x2" hole in the top for the BGA chip area to sit on >and drilled a hole in the side for a power-controlled heat gun. Welded some >baffles inside to guide the air from the heat gun to the square hole.   I'll make it simple for you. Hot air does not transfer enough heat by convection. Close in, radiation is a far more efficient heat transfer mechanism. Loose the hot air gun, hair dryer, or flame thrower, and switch to something that resembles an IR source, such as a heater.   >Top gets heated with a commercial SMT rework heat gun with precise air >temperature control.   Again, lose the hot air gun. I have one of those. It will work with a nozzle that is made for the BGA chip. I only have one size (forgot which one) and that works because *ALL* the hot air lands on the BGA top. That's not the case with just blowing hot air in the direction of the BGA. When I tired that, I found that it took me about 30 minutes to heat the BGA top to 220C. I could do the same with the proper nozzle in about 20 minutes, or with an IR heater in about 10 minutes. (The times are from memory and may be off somewhat).   >My air compressor is running wide open and I'm taking all the >air flow I can get.   Your air compressor is cooling the chip. Try the same wattage heater with slow or fast air. You'll find that the final temperature of the slow moving air is much higher than the fast air.   >thermocouples.   >What I don't know is what air temperature I should be using from the >heat guns.   It doesn't matter. Monitor the BGA case temperature and do whatever it takes with the hot air gun to make it happen.   >I was hoping to avoid a bunch of experiments to determine it >empirically.   Man did not discover how to use fire without someone getting their fingers burned. I could work out the thermodynamic concepts, but with your uncontrolled setup, it's unlikely to be achievable or reproducible. It think you could forget about putting your finger in the fire, but a thermometer or thermocouple would work nicely. One measurement is worth a whole bunch of guessing.   >Would be nice to have a target temperature to start >from.   I gave you that in my previous rant. Somewhere between where the BGA solder reflows, and where the solder paste starts to soften. My guess(tm) is between 200C and 225C.   >This site is interesting: >https://www.youtube.com/watch?v=c_Qt5CtUlqY   Stencils and solder paste work very will with BGA chips. Good video, but I wouldn't try that with a 400+ pad BGA chip.   >I hava a Maxtra 852D+ rework station.   I have exactly the same soldering station, except it says SAIKE instead of Maxtra. Not great, but good enough and the price was right.   >the air temperature 30C lower than the digital readout. >Very small changes in position make radical differences in the >measured temperatures.   Yep. The thermocouple running the display is near the nozzle end in the hand piece. By the time the air has gone to the nozzle, it has cooled down quite a bit.   >I seek less ambiguity ;-)   There is no one answer because everyone's setup is radically different. I just want to fix my backlog of dead boards and move on to something more interesting. Good luck.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

jurb6006@gmail.com: Feb 12 12:49PM -0800 Vinyl Engine has one for the 350. Really, from what I have seen when something has a model nuber like 353 and you find info on one that says 350, it is mostly the same. It may have been just a different cartridge really.   Here is a driect link to that manual :     http://www.vinylengine.com/library/jvc/al-f350.shtml   however you need a membership to get it. If there is soem reason you can't get a memebership I could Dropbox it.   But if you are going to be fixing all this, you should get memberships at hifiengine, vinylengine and probably audiokarma. All free.

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