Harbor Freight 90amp Flux-core Welder- Teardown! - Page 1
Forum section: electronics / general

author: FenderBender
author_rank: Super Contributor
timestamp: December 25, 2012, 07:54:38 pm
content: Merry Christmas to all celebrating today. And if you are not, hope you're also having a good day.My dad knew I always wanted a welder so he bought me one from Harbor Freight. Awesome. It is listed as $90USD.I thought I'd find a real POS inside when I opened it up, but surprisingly it looks pretty good! I haven't tested it out yet. Never welded in my life! But electronics wise, it's pretty bare, but it looks like our Chinese friends did a pretty nice job on this.I can't really fault it. It actually looks well made. All wire connections on the board use sockets! No desoldering if repairs are needed. Soldering looks like a good quality reflow. The underside of the board is clean. And yeah, Chang capacitors. But it's very simple. So, IF something goes wrong, I can probably fix it.Here are some pictures.

author: ales22
author_rank: Contributor
timestamp: December 25, 2012, 09:48:21 pm
content: Hello, it looks good. Unfortunately, I didn't work with MIG or flux-core welder. But I'm quite experienced with MMA machines and I advise to everyone NOT to buy the cheapest ones (with classic 1-phase AC transformer). Professional transformers (3-phase, output rectifier etc.) are OK, but also for very different prices and too big and heavy for garage. I think MMA inverters are very good, maybe even the best for hobby use - cheap, lightweight and works very well.I love this machinehttp://www.svarbazar.cz/phprs/image/200905061901_gama145old_5.jpgit's obsolete model, but current models are almost same.Please, let us know about your results with the flux-core welder.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 25, 2012, 10:51:55 pm
content: A number of years ago, before HF was all over the place, I bought a MIG welder from Northern Tool. I think that was a 150A machine.That was a major disaster, the feed roll was eccentric which caused the wire feed speed to vary up and down. They used a fairly basic motor speed control based on back emf, but the speed varied with the selected voltage.Basically, the cheap machines cut corners on feed mechanisms and copper in the transformer, heatsinking, power rating of semiconductors, etc ... The low end machines actually work pretty well, all things considered, but kind of fall down when you push toward the high end of their capacity.On mine, I threw out the entire wire feed unit and built a new one from scratch, throwing in a bunch of extra features like post feed gas timeout, a gas purge switch and a wire feed jog. I also ended up replacing the rectifiers and adding a filter cap or two. By the time I finished, it was a pretty good welder and had performance comparable to a large Millermatic 250 MIG, which I have since acquired. Other than the duty cycle, it works pretty well now. On the top range you could only weld 1 minute out of 5 or the transformer thermal cutout would cut off. The Miller can run 150A at 100% duty cycle all day.The very coolest tool in this space has got to be a plasma cutter. Cuts 1/4 steel plate like a hot knife going through butter. Now that's awesome.

author: Psi
author_rank: Super Contributor
timestamp: December 25, 2012, 11:48:12 pm
content: I bought a 200A TIG/MMA Jasic WSE200P not so long ago. Works well and construction is quite good.

author: FenderBender
author_rank: Super Contributor
timestamp: December 25, 2012, 11:59:25 pm
content: I've heard that the wire-feed motor in this one is kind of a piece of crap. It looks replaceable if it goes.I know next to nothing about welders so I can't tell you much other than what I can visually observe.I found it interesting that there's no huge heatsinks or big power transistors or anything in here. Must be a primitive kind of design?What generally goes wrong in the wirefeed mechanism?

author: IanB
author_rank: Super Contributor
timestamp: December 26, 2012, 12:18:22 am
content: What makes you say the transformer isn't laminated? It certainly is, as can be seen in the pictures.The reason the inside doesn't look like a PC power supply is because it uses the traditional, robust design with a big transformer and adjustable taps. It's exactly the design you want. No electronics to blow up. Don't knock a good thing.

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 12:40:29 am
content: Ian, I'm a dumbass. That's why.I looked up the definition of laminated core and I was wrong. I thought a laminated core was a core with the black coating on it. I thought that was lamination. Well in that case. Good.I like it! Don't get me wrong. Just wondering what the difference in topology is? More power density with that kind of design?

author: MikeK
author_rank: Super Contributor
timestamp: December 26, 2012, 03:09:07 am
content: I've had this welder for a couple years now. It's decent within its limits. It does 11 gauge (0.125") really well if you put the heat on high, wire speed at 8, and make slow passes. Haven't tried anything thicker, but I wouldn't expect it to do well. And it doesn't do thin gauge well.WeldingWeb has a section for HF tools and this welder does get favorable reviews. There's also a Yahoo! group for it, but I don't think it's very active.If you get into welding more, splurge for a real MIG. I'll probably get a Hobart MIG soon.Mike

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 03:24:04 am
content: Thanks. Yeah well I don't have much to weld...right now. That might change.

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 04:22:13 am
content: After a bit of reading, it seems some of the weld-heads are appalled by this welder because it's AC at the tip.So it got me thinking...How can we make this a DC welder.It seems the most popular way is to install a bridge rectifier then a filter capacitor in parallel with the output and a choke in series.Any ideas on finding suitable component values? I'm guessing the choke might have to be custom. Not sure what kind of inductance is necessary?Any ideas?

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2012, 04:40:17 am
content: You will not need a choke, the transformer is one in itself. You will need a 200A set of diodes though, rated at 100PIV at least. At least you have a fan to cool them.I took my MMA welder and added a single 60A diode to get a DC output and a 40A breaker, so that I can use it as a very dirty battery booster ( trips breaker after around 2 minutes of charge) for emergencies. Added a 120mm fan in the holes provided, though it only runs when the welder is not in use, as the stray field of the transformer when drawing current stops the fan. Still provides a better duty cycle, as the cooling off period is now shorter.

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 05:06:44 am
content: No capacitors?

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2012, 05:48:45 am
content: If you can find one with a ripple current rating of 200A that fits in the case then fit it, otherwise don't bother. If you want add a few 4.7uF 250V film units across the bridge output to provide HF smoothing, along with a 10K 10W discharge resistor. You will probably want to use some 1uF 160V units and a series 10R 5W resistor across each of the diodes to do some snubbing of fast edges. Remember all the wiring will have to be at least as thick as the secondary winding wire to handle the current. Soldering will not be with any wimpy soldering iron, at least a 500W unit will be needed, or a small gas torch.

author: IanB
author_rank: Super Contributor
timestamp: December 26, 2012, 09:09:32 am
content: Before modifying the welder it might be an idea to get fully familiar with its operating characteristics in its original form. That way you will be able to make an accurate judgement about whether any modifications made have improved things and by how much.If you do modify it don't forget that diodes for that kind of current rating will need big heatsinks.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 26, 2012, 11:55:59 am
content: I am a welder by trade and by family (6th generation)... But I am not understanding whats the point of buying a junk machine and wasting the time and money to improve it

author: IanB
author_rank: Super Contributor
timestamp: December 26, 2012, 12:18:17 pm
content: Quote from: TorqueRanger on December 26, 2012, 11:55:59 amWhat are the things to look for when choosing a welder? Presumably price alone is no guarantee of quality, neither I imagine is "more amps"?For occasional hobby use it would be hard to justify an expensive professional tool, just as it would be hard to justify buying one of the Agilent scopes Dave likes to play with. So what's "good enough"?

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 05:20:40 pm
content: Quote from: TorqueRanger on December 26, 2012, 11:55:59 amI have never welded in my life. Nor has anyone in my family or anyone that I know. A name brand machine, say a Millermatic, starts at around $700. Yes, I am sure it is easier to work with, but for the amount of use I expect this welder to get, I do not think it's worth it. $90 is a hell of a difference from $700. I'm sure you get some great benefits with a "real" welder, but for the time being, I want to see what I can do with this.The modifications, if done, would probably not exceed $50-60. So the total price would still be pretty low. Still determining whether I want to it or not.As far as making the big solder connections, biggest soldering iron I have is 200W I believe...hmm

author: MikeK
author_rank: Super Contributor
timestamp: December 26, 2012, 05:50:18 pm
content: I agree with Ian. Use and enjoy it first. You might be satisfied without doing any of your mods.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 26, 2012, 07:35:27 pm
content: For $90, you get a tool that lets you do something that you couldn't do before. It does have limitations. If you do a reasonable amount of welding, you'll end up wanting a tool with fewer limitations.One of the big upgrades is to ditch the flux core and go for real MIG. Some flux core welders offer an adapter kit; I don't know if this is one of them.Anyway, have fun. Get yourself a good auto-darkening helmet (not the $49 HF special), it will make your life a whole lot easier. Wear good protective gear, the arc will UV burn unprotected skin and nothing pulls your attention away from the work like a hot gob of metal burning through your shirt.

author: FenderBender
author_rank: Super Contributor
timestamp: December 26, 2012, 09:16:02 pm
content: Thanks. Yes. I won't be modding it any time soon. Now that I think of it, I never seem to have such good luck modifying equipment.Well darn I was just going to buy that autodarkening helmet...I guess I'll go splurge at Home Depot for a Lincoln. What's wrong with it? (by the way)See what kind of welds I can produce with it.

author: MikeK
author_rank: Super Contributor
timestamp: December 26, 2012, 09:33:42 pm
content: Also get a can of PAM cooking spray. Put down before welding it helps to limit spatter, which you will get quite a lot of with flux-core. I also ditched the factory wire and picked up a spool of Lincoln wire from Home Depot.

author: PuterGeek
author_rank: Regular Contributor
timestamp: December 27, 2012, 12:20:16 am
content: Quote from: FenderBender on December 26, 2012, 09:16:02 pmThe cheaper Lincoln that Home Depot is probably a worse deal than the Harbor Freight ones.For the price difference and your lack of experience I would buy the better Harbor Freight helmet if you have a store nearby. The online reviews for them are pretty good from what I've read.I'm sure there are better helmets just like there are better welders. If you think it's junk after you've used it a little return it within 30 days for a refund.

author: FenderBender
author_rank: Super Contributor
timestamp: December 27, 2012, 12:41:10 am
content: Quote from: MikeK on December 26, 2012, 09:33:42 pmMy dad actually did that. Read poor things about the HF stuff.

author: MikeK
author_rank: Super Contributor
timestamp: December 27, 2012, 02:10:22 am
content: Quote from: FenderBender on December 26, 2012, 09:16:02 pmI have the HF auto-darkening helmet too. It works well. It's usually on sale, too.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 27, 2012, 03:27:09 am
content: Quote from: PaulAm on December 26, 2012, 07:35:27 pmThis. Even worse is it burning through your plastic sneakers and sock. Wear high sided full-leather boots, full trousers, and leather jacket and gloves. No exceptions. Oh and btw, the arc UV doesn't just burn exposed skin. It also slowly disintegrates some types of cloth.I second the 'leave it alone, use it to learn, and then someday buy a better one if you need it' comments.Professional MIG machines are very nice, with the downside of having to pay rental on a gas cylinder. Here in Australia it's not possible to purchase the cylinders to achieve zero 'idle' cost. You can only rent them, and that's expensive. With a MIG, a TIG (different gas needed), and an oxy set, the yearly cost for those four gas cylinders dwarfs all my other yearly running costs together.If you keep a lookout, you can likely get a very good second hand industrial welder of whatever type you decide you need, for relatively little cash. Maybe even free if you are lucky. For instance my MIG (Esab Smashweld 250) was a gift, as 'broken', but was easy to fix.Also, watch some youtube howto videos on welding, and buy some secondhand welding theory books (abebooks, amazon etc) asap. Bad welding habits acquired in self-taught mucking around will be very hard to unlearn later on.Another thing - get yourself an angle grinder or two. A welder without an angle grinder is like a rowboat without oars. With them together, steel is your malleable friend. Partly cos you can entirely undo your mistakes, and do it over. Side grinding wheels for beveling edges for welding, removing scale, spatter and smoothing welds; thin cutting disks for getting pieces in the right shape. Actually I keep two angle grinders, so I don't have to keep changing disk type all the time.

author: FenderBender
author_rank: Super Contributor
timestamp: December 27, 2012, 03:45:31 am
content: Quote from: MikeK on December 27, 2012, 02:10:22 amYep. I picked it up for $37 today.

author: FenderBender
author_rank: Super Contributor
timestamp: December 27, 2012, 03:46:02 am
content: Quote from: TerraHertz on December 27, 2012, 03:27:09 amUnderstood. I'll go see if I can find some sort of apron of some sort.

author: SeanB
author_rank: Super Contributor
timestamp: December 27, 2012, 04:44:39 am
content: Don't forget a hat as well if working in the sun. Nothing worse than a burnt back of neck, along with some of those little splashes can fly up a considerable distance and land in your hair.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: December 27, 2012, 08:42:49 am
content: Don't weld anything galvanized, the zinc will vaporize and give you a kind of of brain rotting "happy". Actually the least healthy thing about welding is all the metal vapours. James Huberty the San Ysidro Mcdonalds massacre (1984) shooter was a welder who quit/was fired from his job because he said it was making him crazy. While he had a previous record of mental illness and violence his post mortem blood levels for cadmium were off the charts and should have been fatal. I hobby weld and don't worry about it too much but I keep a fan at my back.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 27, 2012, 12:44:27 pm
content: Huh. You learn something every... something. I didn't know about zinc being harmful. Though I avoid welding zinc plated stuff just because it's so messy.Did know about the 'smooth machining' mild steel alloys that include an amount of lead to make it cut better on a lathe. Don't weld them either.The one that really freaks me out, is brazing fluxes consisting of fluorine and/or boron compounds. Just great.

author: akcoder
author_rank: Contributor
timestamp: December 28, 2012, 03:28:34 am
content: Quote from: FenderBender on December 26, 2012, 05:20:40 pmMy buddy gave me his old Daytona (a cheap Italian made welder - what china is to electronics, Italy was to welders) 220v welder a couple years ago because it would go into thermal shutdown. I let it sit for a year plus before discovering that the bearings on the fan dried out and causing the fan to spin at minutes per revolution.After fixing the fan and putting in a distribution bus so I could reverse the polarity to do flux-core, its turned into a very handy tool. I end up using it a lot more than I thought I would. So much in fact that the reverse polarity mod was short lived and I ended up getting a bottle of 75/25.I've made a light bracket for my snow blower, fixed a stripped out stamped "nut" that held the handle on said snow blower by grinding off the stamped piece and welding a 3/8's nut in its place. Plus countless other things for myself. And once people find out you have a welder... :-)weldingtipsandtricks.com is a good site to learn welding techniques, he covers mig, tig, stick.-dan

author: akcoder
author_rank: Contributor
timestamp: December 28, 2012, 03:46:20 am
content: Quote from: TerraHertz on December 27, 2012, 03:27:09 am

author: SeanB
author_rank: Super Contributor
timestamp: December 28, 2012, 04:51:47 am
content: 2 grinders very useful. Actually getting the wire brush cup for the grinder works better then the bench grinder. Wear eye protection when using the grinder cup brush, those wires fly everywhere when they break off, and are merely annoying dug into your arm but very bad in your eye. Having an Opthalmic surgeon saying don't blink while he is bringing a needle into focus on your eye is not fun.

author: G7PSK
author_rank: Super Contributor
timestamp: December 30, 2012, 06:01:58 pm
content: The reason you 'weld zinc is that the fumes give you metal fever this is the same thing that the tank gunners got in the 2nd WW, brown trouser time for a day or two after breathing too much zinc fumes. The main problem with those little MIG/MAG welders is the live torch and some don't even have a gas solenoid let alone pre and post flow burn back etc. Got to a welding school and have a go there or even a proper welding distributor who will usually have a demonstration machine or two, in my experience those cheapie machines are so awful that it makes it very hard to learn to weld with them. I once bought a SIP machine (made in Italy) as it was offerd cheap to me and I was looking for a machine for site work at the time, big mistake I ended up getting so pissed of with the poor duty cycle and the wire feed perpetually producing birds nests that I borrowed a JCB with a 4in 1 front bucket picked the thing up and gave it a squeeze then dropped it into a skip and that is where all such crap belongs.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 31, 2012, 01:35:19 am
content: Quote from: akcoder on December 28, 2012, 03:46:20 amSigh. Remind me again how Australia is the land of excessive regulation and corruption.The gas companies claim 'rental only' is necessary to ensure regular cylinder safety testing. They'll trot out horror stories of old gas cylinders that were used for 20 years on boats in salt spray, exploding during filling, etc. Therefore a guy like me who'll have the cylinders sitting in a clean hobby workshop for years and sometimes might not even use them all year, and will go several years between refills, can't own them and must pay rental. Because when youdoneed them, you really need them.It's entirely coincidental that the gas companies make most of their income from cylinder rental, and the eagerness of the government to legislate private cylinder ownership out of existence hasnothingto do with cash incentives to those responsible.This situation totally sucks.Even garden variety propane cylinders have a rort here - they are stamped with their manufacturing date, and illegal to refill from 5 years after that date, unless inspected, retested, and restamped. But try to get a cylinder actually retested... ha ha ha. Nope, buy a new one. Never mind that the old one isfine.Well, at least there's a workaround for that, which involves having one large 'in date' cylinder, and as many other random aged cylinders as you like to use.QuoteHmm... well at least I'm only old, not old and feeble yet.Why didn't you buy a smaller one? You can get cylinders you own refilled, right?QuoteCome to think of it, just realized I have three angle grinders. The third one I bought to build into a tool I made to precisely grind down weld beads on MIG welded stainless steel tubing. This thing:

author: G7PSK
author_rank: Super Contributor
timestamp: December 31, 2012, 05:18:08 pm
content: Gas cylinders are rental only in the UK other than the small DIY cans that you buy and then throw away, I have known people get an old CO2 cylinder from a pub and then transfer Argon mix into it from a rental one then take the rental back and put it off hire until next time. All you need is two cylinder connectors on a piece of high pressure pipe but you have to be very careful not to let the pie or cylinder get too hot as that would be a very embarrassing bang.

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 31, 2012, 05:43:02 pm
content: Years ago the only way to get cylinders was to lease them, but that changed. I have a number of half size cylinders now. They're all filled on an exchange basis so I never have to worry about recertifying them either. The half size is a little easier to move around and, given the amount of welding I do, lasts for a long time.The last time I swapped out my acetylene cylinder they changed from the flat top tank that's been used forever to the normal style gas cylinder.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 01, 2013, 12:11:26 am
content: Quote from: G7PSK on December 31, 2012, 05:18:08 pmTransferring works great for propane, since you're pouring a liquid from one cylinder to the other under gas pressure (using the vents to create the 'push') and so you waste only a tiny fraction of the stuff you paid for.But transferring shield gas results in losing 50% of the gas - it's still in the rental cylinder when you return it. Unless you have multiple storage cylinders, but you're still leaving 50% of the initial source amount on each transfer. Only way around this is to have a high pressure transfer pump, and I've never found a source for such a thing. Plus there are potential problems of contamination, explosion risks for oxygen, and complete impracticality for acetylene due to the necessary solvent in the tank.PaulAm, which country are you in? America?

author: Stonent
author_rank: Super Contributor
timestamp: January 01, 2013, 04:29:07 am
content: In the US, propane for gas barbecue grills is usually exchanged. Most grocery stores have an exchange area where you turn in the old tank for a new one. However you can also usually take the tank to a camping supply store or RV park and get it refilled for cheaper.The place I used to work had a company called Matheson Tri-Gas across the highway that sold CO2, Argon and other gasses used in industrial environments. They could refill cylinders or come on site and refill cylinders and tanks.Cylinder exchanges are fairly normal as far as I know in the US. That helps keep old dangerous cylinders out of production.

author: G7PSK
author_rank: Super Contributor
timestamp: January 01, 2013, 04:24:51 pm
content: Quote from: TerraHertz on January 01, 2013, 12:11:26 amIt works due to the high cost of rental (BOC charge £135 plus per year for ) so wasting gas is far cheaper if half a cylinder costs less than a full years rent A PD size costs almost the same as a W size and the gas fill costs twice as much per CU M. so decanting can work very well for a small user.

author: SeanB
author_rank: Super Contributor
timestamp: January 01, 2013, 04:32:18 pm
content: I have had 2 cylinders that the gas place refused to fill this year. I just went and got a new one, then vented the old one when it was empty and filled it with water, then cut it and scrapped it. Been doing it with disposable cylinders, though those normally get recovered to a good vacuum then have a big cut made in them, as otherwise the scrapyards do not want them. Looking for a cylinder of either argon or dry nitrogen and a regulator. Helium will do as well. Those unfortunately need a rental, portapack cylinders do not, they are done on an exchange basis.