#374 Harbor Freight 90A "MIG" welder upgrades

how do you turn a $99 MIG welder into a $250 mega elder for only 30 bucks for those of you who have been following my channel for any length of time you know that I went out and bought a Harbor Freight special $99 MIG welder and I've done a lot of a lot of welding with it subpar in quality and some of that was my fault but as it turns out not all of that was my fault and I happened to be reading some of the reviews on the Harbor Freight website long after I purchased this $99 MIG welder and discovered that this really isn't a MIG welder at all because to qualify as a MIG welder it needs to have a DC output this has an AC output which is mediocre at best and creates a lot of splatter which is one of my number one complaints with the with the old welder and the guy who made the review on the Harbor Freight website said that he converted his and that got me interested so I did a little bit of research and found out quite a bit about MIG welding learnt learned a little bit more about the finer details and what it takes to actually turn this into a true MIG welder the end result that I have today is a completely different machine so let's go through some of the changes that were made I will include the drawings and schematics and I'll be as detailed as I possibly can without running on and on and on about all them all the minutia that you probably may not want to know but I will go over the basic details of it and there's a lot of information you can find online about converting an AC unit to a DC unit and making it a much better much better welder all right first thing I'm going to do is I'm going to take the left side cover of the unit off as you face the front of the unit so I'm going to lay it right side and to speed things along I'm just going to use my power drill side cover just comes off like that so now that the case is off we'll take a look at the internal workings alright the very first things that you see immediately are this three-phase 100 amp 1200 peak i peak inverse voltage full wave bridge got this on ebay $15 delivered these capacitors that you see here are salvaged from UPS's that i took apart these are good very high quality capacitors very low ESR which stands for equivalent series resistance meaning that they can circulate a lot of current without heating up that's very important when you're selecting your capacitors and it's always better to use a bunch of smaller capacitors than it is to use two or three large capacitors so there it is illuminated a little better with the camera light you can see how I've got them wired together I have a total of eight capacitors for a total of close to sixty thousand microfarads so they're just about seven thousand average seven thousand microfarads each at anywhere between 35 and I'm sorry at anywhere between fifty and sixty three volts for a working voltage the two output terminals of the DC bridge rectifier go to the capacitor bank which also has a 150 ohm 5 watt bleed resistor on it so that it will not retain a charge for very long and it also goes to the to the clamp to the cable that goes to the clamp and this wire here leads to the cable that will eventually lead to the mig welder wand deep inside you can see on the bottom I have secured with a cable tie right here a coil or a inductor the inductor goes in series with the output of the bridge rectifier in between the output of the bridge rectifier and the MIG welder wand alright so that this is the connection right here coming on the other side of the choke and then it's just but spliced into the connector that runs up through the bottom of the upper set upper deck of the MIG welder to the to the wand on the other side you can barely see it there's this there's a transformer that transformer is a $15.00 purchase which is the the second 15 dollar purchase adding up to $30 worth of parts that I actually bought them to upgrade this it is a 25 volt with a center tap 2 amp transformer one of the deficiencies of this MIG welder is that the motor the power supply for the motor that drives the the wire through the through the cable to the wand is that it took its power directly off of the secondary of the transformer so you had roughly 24 to 28 volts ac depending on what power level you selected on the MIG welder and this red and black wire went to this connector on the pc board and the problem is when you start welding the voltage on the transformer secondary will sag when the voltage on the secondary sags the speed of the motor sags with it and then you get a very unsteady feed rate with the with the mig welder and that is very undesirable you want to you want to set feed rate you want something that you can count on regardless of whether you're welding or not welding so the solution to that is to cut cut the wire from here make sure that you insulate it and then take the wires that you cut and splice them I don't know if you can see the crimp caps in there yep you can see the crimp caps those are the crimp caps that lead to the secondary of the transformer that I purchased that is down on the other side this secondary is also this transformer is also screwed to the bottom of the upper deck of the MIG welder I'll show that to you in just a moment one final thing I want to show you before we proceed to the other side of the of the welder is this this large relay on the PC board for the motor speed control is a relay that actuates the primary of the main transformer inside the mig welder when you pull the trigger this relay is actuated and this is what applies voltage to the primary the input the voltage input comes in on this black wire right here and exits on this wire right here which is the transformer primary though the large transformer primary you can see a little piece of wire here that I have spliced into it and then put heat shrink back over the top of it after I spliced it and soldered it that leads to the primary of the of the secondary I'm sorry that leads to the primary of the transformer that I added so the transformer is only live when I pull the trigger and that's when D or AC is applied to the printed circuit board down here supplying power to the big big wire feeder appear looking at the opposite side of the mig welder got a lot more space you can see got another look at the at the transformer incidentally the core of the transformer is two toroid cores that are stacked on top of one another and there are 27 turns which is all I could fit I would put more if I could 27 turns of number 8 gauge wire heavy insulated 8 gauge wire probably could have gone with even a not quite as thick insulation and gotten more turns on there but it is what it is and here is your transformer you can see how it's screwed to the bottom side of the upper deck all right and these are the wires that lead to the fan the cooling fan at the back of the MIG welder black wire on the power cord coming in is the AC hot comes to the main power switch down below which is the terminal closest to you on this side and then those three wires that are connected to the power switch that you see tie wrap together there's one black and two red coming off of that actually two black and two red coming off of that one thin black is is this wire right here this goes to one side of the primary for the transformer that I added and then the other side is crimp capped to the wire extension that runs to the output of the switch relay this particular MIG welder is a modified version of one I guess that they used to make that was called a hot tip and the hot tip means that as soon as you turn the power switch on on the front the tip was always hot meaning it was live it had power on it and then the only time the only difference was when you pulled the trigger it actually started to feed the wire but leaving it hot all the time was not a good idea so they they upgraded it a little bit and put in that relay so that the tip is only hot when you the trigger on the on the MIG welder and that gives you a good way to tap off and switch the primary for the transformer that's been added here's an example of the best weld that I could that I could come up with using AC for the MIG welder all right it's blotchy it's not a smooth not a smooth weld at all it's adequate but certainly Stan could stand a lot of improvement and I want to show you now just a piece of scrap material that I was playing around with there's an example of a weld that I made this one right on the very on the very corner right here all right very smooth no puddles and if you look at the metal you can see it's very deep into the metal it's halfway through that quarter-inch piece that was a really smooth weld here's another one right at the very edge towards the front right here very little splatter now very hot weld very smooth application it's a whole different machine so that's it for the modification the only other thing that I'm going to do differently is I found that when you use the welder the actual secondary voltage drops from a no load voltage of anywhere from 24 to 28 volts depending on what range you've selected which also affected the motor speed by the way now the motor speed is unaffected by what range you select but when you're actually welding because the motor was connected to the secondary of the of the main transformer that voltage actually sags to maybe 16 or 18 volts anyway while you're welding so a 12 volt secondary transformer under no-load is going to rise to about 15 16 volts which is what you want for the motor anyway I found that when I use the 25 volt secondary I now had to put the the speed control around to where I was up around four or five before so what I'm going to do is I'm just going to use the 12 volt tap instead of the 24 volt tap on the transformer for the motor drive and that should get me back into the same calibrated range roughly in the same neighborhood as it used to be before and that's that's all there is to it now this is called a Chicago electric welding MIG welder I will be changing the name it will now be called the zero electric welding MIG welder that's all for now as always please rate share comment and subscribe and peace everyone okay so I need a little more practice I'll get there I'll get there eventually peace everyone you you you you

Channel: Zero Labs

Views: 157,859

Keywords: Harbor Freight, MIG, welder, 68887, DC, bridge, rectifier, capacitor, inductor, choke, mods, modification

Id: ozjFq5KXm1U

Length: 16min 30sec (990 seconds)

Published: Wed Jul 23 2014