Handler 120 diodes

[wzltech]

Hi all,
New to the group so be gentle . Pleased to have found this forum since I’ve already gathered a lot of useful info and the tone of the participants is first rate (polite, respectful, and helpful). Now to the questions.

Diodes on my HH120 seem to be bad, both have continuity in both directions.
Do these go out fairly regularly? (not per machine, but for the entire HH120 population)
What usually causes it, just age and heat?
Could a poor external supply circuit (15amp) cause it?
If one goes bad will it usually take out the other one?

When replacing the diodes would it make sense to replace the capacitors that are attached to them (C2, 3 from the wiring diagram)?
If one of those capacitors was poorly attached (soldered) could it kill the diode? I wouldn’t think so given its apparent purpose, but what do I know.
Are there any significant reasons I should use OEM “Hobart” diodes as replacements given that the welder is out of warranty? I know the diodes are 70 amp, 200 volt, but I’m not sure about their “speed” (i.e., fast, ultra fast, etc.). Wouldn’t a diode like this (see link) work just as well? Or are there other specs to consider (which ones? I like to learn)? http://www.surplussales.com/Semicond.../Diodes-3.html (the upper left one)

I don’t have anything against supporting Hobart, but I imagine I might have less trouble finding “equivalent” diodes in stock at an electronics supply house than at a welding center, I’m assuming they wouldn’t have them in stock and imagine it could take awhile to get them. Besides, I like to have options/choices. Anyone have experience with getting parts for this unit? Guessing cost would be $10-15 each, ballpark?

Guess that’s enough for now. Thanks in advance for all thoughts, advice, insights, it’s greatly appreciated.

Don
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If I’m not learning I must be dead....or might as well be.

[Mike W]

Welcome wzltech. Did you isolate the diodes when you checked them? If the ones in my 20 year old 200 amp Hobart ever go bad, I have some bigger ones to replace them with. What were the symptoms to make you think the diodes are bad?

[Hobart Expert Kevin]

wzltech,

Do you have the spec. number off your Handler? We most likely will have them in stock here.

Kevin

[wzltech]

Kevin - The Hobart part number on the diode and in the manual is 406170-3 they are/were apparently made by International Rectifier (IR on the diode), but there is no cross reference for it on their site or any other so I'm guessing it was a part number just for Hobart. The only other info on the diode is "Italy 9636" and the diode symbol. I haven't found any info regarding the 9636 number. The diode is a stud mount (stud's about 7/16" long by 3/16" diam) rated at 200 volt (from the manual) and 70 amp (from the mouth of Hobart). The Handler 120 is Model (version?) 7144B-1, 90 amp output etc. The only other info I've been able to find is that now the diode is a Miller part also, guess Miller took over, but it's basically the same number, think they just add "MIL" before the number and maybe a couple of zeros after the dash. Nobody seems to stock them, at least that I've called so far, but they can get them from the factory for about $15 each (welder uses 2). No idea how long it takes to get them, but may have to find out.


MIKE W - Problem started after welder had been sitting unused a few months. I know, terrible, but I was busy making sawdust instead of sparks and the two don't mix well.
I took the welder to a buddy to use and it sparked once upon striking arc and then tripped garage breaker. I was there so I know he's not giving me some story. After that it wouldn't do anything but trip the breakers when the trigger was pulled. We tried different circuits since his garage is only 15 amp, but still no good. I doubt just having it on a 15 amp curcuit would kill the diodes or cause it from working since it's been used on them before. Would expect it to just limit output or trip breaker if duty cycle is too high. The fan turned on normally at all times.

When I got home I tried it in my garage and it wouldn't usually trip the breaker, unless I manually held down the contactor (NOT with my fingers), but the contactor would chatter and there would be obvious sparking within it. Started troublshooting by opening the contactor and cleaning up the contacts which had obvious arcing (carbon, some minor pitting). They say you can't service them, but I disagree. The contactor pull down coil showed no problems or obvious shorts and the continuity was good. After that just started following and isolating circuits.

There was good voltage to the contactor coil from the fan transmotor, low voltage there can also make them chatter, but I doubt they would spark the same. Eventually got to isolating the transformer and then the wire feed would work and the contactor would act normally. The diodes were still part of the transformer circuit at the time. Figured out something was shorting when the 2 "main" windings of the transformer were connected. (Was hoping very strongly that the windings weren't shorted.) There is a bolted connection in the HH120 that 2 of the windings ends go to with the other ends going to their respective diodes on the "output rectifier" aluminum heatsink plate. Further isolation and continuity testing revealed that the windings are fine, but that the diodes have continuity all the time in both directions. Isolating either diode from the circuit with the bolted connection still in place will allow the contactor and wire feed to function normally, but obviously you would not be able to weld this way since technically you'd only have half the transformer's output and the other diode's still bad. It just isn't shorting anymore.

The only obvious problem I found, besides the diodes being bad and that wasn't obvious, was one of the "small" capacitors that attaches to the diodes to "smooth out" the output current was loosely attached at the diode end. But I don't think this would cause a diode failure, just make welding less consistent maybe, but I could be wrong.

Anyway, sorry for the long post, but maybe it will help someone else.

Don

[Hobart Expert Kevin]

Don,

406170-003 is a good part number and we do have them in stock here in Appleton, they list out for $13.36 each. Any Hobart or Miller distributor or service station can order them for you and have them in a few days.

Kevin

[Mike W]

Good troubleshooting wzltech, sounds like the diode just shorted out.

[wzltech]

Just to follow up. I got the new diodes in today and welder is back to it's happy little self. Nice when troubleshooting actually works. Let the sparks fly.

FYI: I ordered the parts from my local Praxair (Hobart/Miller dealer) and they arrived in just about a week. $15.58 each, but nothing added for shipping (of course, I'm sure that is factored in somehow). I guess diodes are a little cheaper in Appleton, WI (see HE Kevin's earlier post). And for those interested in trends in global economics, the diodes are now made in India instead of Italy. C'e st la vie.

Happy welding all

[jtc]

wzltech,

I just got a welder from work that I was using and just stopped working and the company decided to replace it and let me take it home and I think this could be the answer to my problem also. the fan runs but when I pull the trigger and hold it long enough it pops the breaker and the wire feed motor won't turn and I get sparks and chatter from the relay.If you or any one can offer any other advice it would be appreciated.

[Tirzah1981]

fan runs but motor doesn't turn and chatters when trigger is pulled

I have a hobart Handler 120 and like jtc it does the same thing: the fan runs but when I pull the trigger and hold it pops the breaker and the wire feed motor won't turn and I get sparks and chatter from the relay.
Also the first time I ran it, it tripped the breaker right off the bat. Not only that I tried a couple different plugs around the shop and with the same result, tripped breaker. Someone was saying that if I have insufficient power I might ruin the diodes. I feel like this could be it. But I have no confirmation in that I haven't found any troubleshooting info other than this.
It sounds like it could be the diodes, but I don't know how to check this and had trouble following wzltech's post. Can anyone clarify how to check the diodes?
Thanks for any help you can offer.

wzltech,

I just got a welder from work that I was using and just stopped working and the company decided to replace it and let me take it home and I think this could be the answer to my problem also. the fan runs but when I pull the trigger and hold it long enough it pops the breaker and the wire feed motor won't turn and I get sparks and chatter from the relay.If you or any one can offer any other advice it would be appreciated.

[canoecruiser]

The most common failure for diodes is to become shorted. In other words, they no longer stop the current flow in one "direction". If you have a voltmeter that can measure resistance, one of the ranges on the range switch, assuming it is not automatic ranging, should have a diode symbol which is a triangle pointing to a straight line at 90 degrees to the long axis. It's hard to envision but if your meter has it you'll understand. With the two leads connected to the diode terminals, it should indicate some resistance value indicating some current flow and if you reverse the connection, there should be no indication of flow. A shorted diode will cause the meter to indicate the same as if you held the two leads together, and it will act that way for either direction you connect the leads to the diode.

I have seen folks without a meter use a 12 volt automotive lamp like an 1156. Connect the lamp and the diode in series, and then find a source of 12 volts DC like a car battery. With the combination connected across the positive and negative terminals in one direction the lamp should light; the other direction it should not be lit. A shorted diode will light regardless of the direction and an open diode will not light in either direction. A headlight isn't a great choice since it can pull enough current that a diode without a heatsink can get hot quickly which is fatal to a good diode. I strongly prefer the meter method (I'm an EE by trade) and reasonable meters can be purchased at Lowes or Home Depot for $20 or so. If you talk nice to a clerk at Radio Shack he/she might test them for free.

Apologies for being so wordy.

Canu

[Tirzah1981]

Thanks Canu

I'll have to look into that. I appreciate you being so wordy. It made my job(s) very clear.

[canoecruiser]

Others have helped me so I'm just paying down a debt. Good luck and let us know how you make out.

[Flier]

HH120: no arc, no wire feed, fan runs

Greetings, and thank you for being here!

Follow-on to Don's (wzltech) problem a while back, as I inherited a HH120 (sn WS10028) that worked last year, but not this.

When I pull the trigger, the contactor clicks and the fan runs. The wire feed motor will run with 12V DC applied directly. The continuity of the circuit breaker is good. The diodes measure 43 in one direction and 1 or so in the other, but still connected to the plate. Presume ohms (?). Should I check with them isolated?

Interesting that (at least) two of the female wire connectors were loose where contacting the spade (male) tab of the rheostat and the CB. (The wires are in the motor circuit.) And, I cleaned the contact surfaces of the wire feed rheostat.

What to check next? Could the 50,000 MFD capacitor be bad? How do I check that? What about the thermal breaker that's buried in the coil? Or are the diodes defective?

I'm open to any suggestion including where to get parts, but out here in Halfway, Oregon, repair options are limited. Pretty much DIY or die.

Thanks, Don, for your follow-up on your repair with new diodes. That really helps in a forum like this.

[Flier]

HH120 Fixed!

Reading lots of experiences on repairing HH120, but my fix was so obvious I missed it, and wasted a lot of time.

The problem was that when turned on, the cooling fan ran, but when the trigger was pulled, the contactor 'snapped' but nothing else happened: no wire feed, no arc.

Several of the female spade quick connect wire connectors had lost tension and were loose on their contact points. I can't specify which ones (there were five or six that I have found, so far), but the very last one was out of sight on the back of the contactor ("Definite Purpose Controller") from the large transformer. That one was rusty and loose on the contactor spade.

Fortunately I had found how to test the 53,000 mfd capacitor before spending over $50 on a new one (put some voltage on it and see if it holds after a while), but I did replace the power diodes (found on eBay for 7.95 each, shipping included), all without success.

I found the parts by Google searching the label info: "85HF60" for the diodes, "Definite purpose controller 24V", though I couldn't find the large capacitor cheaper.

Simple, easy fix. Hope this helps someone.

[Jaskim06]

Hello new here, this caught my attention. I spoke to Scott at hobart and he was telling me I have a diode issue, 90% sure. I have a handler 135 115 volt, plugged straight in no extension cord. When I weld on my 30 Ford model a coupe panels for 15 minutes it woks perfect, no hiccups then it seems like the voltage is being turned down to nothing at all and I can't weld. Shut off come back next day and same exact thing. I've looked at these diodes and they're cheap but I want to make sure that's the issue. I was suckered out of almost $300 by a gas welder fix it man who replaced the wire feed assembly. He tested with me and it worked fine, just a proof of working test not a long test. Welder had this issue in first place so I have a new roller assembly that I waited a month on and still can only weld for 15 minute intervals. Any help would gladly be appreciated. I don't know if I should replace the board that costs more than a new 140 Welder, the diodes Scott said maybe the capacitor but most likely the diodes. I'm not a electrician, I've wired my 2 log homes and built them but testing and figuring out what, how to test is painful. I gather only current through 1 way and if both its no good, not at all no good. What would you gents who know what is what do? Thank you again. This has been a 3 month issue. I've about given up and just weld for 15 minutes and say heck with it. Thank you again.