Millermatic 35 and 35s welder help

Discussion in 'General Electronics Chat' started by Fixerman, Apr 23, 2013.

  1. Fixerman

    Thread Starter New Member

    Apr 23, 2013
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    Hello all. This is my first post, so forgive me if I make a mistake or two.
    I am generally very good at locating problems in things and fixing them. That is, in most things that are not electronically based.
    Here is my current problem. I have a Millermatic 35 and a Millermatic 35s both of which I have been able to fix, mostly because the problems they had were mechanical in nature, old mechanical relays and contactor switches, etc. I have five buddies that own non-functioning Millermatic 35's. I have found several mechanical problems with them, and now believe the rest are electronically related.
    I have located schematics for them, and feel that with a little help from an electronics hobbiest can locate test points on the schematics to allow me to compare readings to my machines and keep all our machines functioning. I have basic knowledge of electronics (very basic) and have a digital multimeter. I can recognize schematic components, but have little knowledge as to following the flow thru the circuits.
    Is there anybody willing to help identify test points (as many as possible to narrow down the problems) on my schemetics for touble shooting these machines?
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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    If you have the schematics go ahead and post them along with what you've already checked. I'm curious, what is a Millermatic 35?, I have a Millermatic 175, and the model # indicates the welding current. And I've never seen a 35 amp welder.
     
  3. Fixerman

    Thread Starter New Member

    Apr 23, 2013
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    The Millermatic 35 was made in the early 70's. They were rated at 150 amps. Built like tanks and a lot are still in service. They were the first mig to contain the wire feed drive and the power supply in the same box. I have uploaded (if i did it right) the MM35 and the MM35s. The "s" had the spot weld option, which only means that you can adjust the time trigger is energised before it shuts off automatically. I think the idea is to obtain a consistent burn rate. Each trigger pull gives you one burn pulse.
    On the schematic for MM35s the spot weld board is at the top, fed by the bridge circuit of diodes D51, D52, D53, and D54.
     
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  4. gerty

    AAC Fanatic!

    Aug 30, 2007
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    What is doing or not doing?
    Have you taken any voltage measurements yet?
    Does the wire feed or fan come on?
     
  5. Fixerman

    Thread Starter New Member

    Apr 23, 2013
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    There are varying problems with the 5 units my friends have. That is why I would like help id'ing enough test points on the schematics, so I can take readings from my working units and narrow down problems that way. Plus, I would like to be able to maintain them all in the future, as it would be more expensive for a shop to fix them than they are probably worth.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
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    What we usually do is to walk you through the process a step or two at a time.
    If you just want general guidelines to fix 5 at once here are a few things to check. Power to the unit, per dwg the fan should be running.
    Power out of the transformer, looks like 3 sets of windings. There are circuit breakers on 2 of these, the third is the welding winding, no breaker, but goes to rectifier diodes.
    I've seen the trigger circuits go bad in the liners.
    If you come back for help, let's keep the questions confined to 1 machine at a time, way less confusing for everyone involved....And to those trying to follow.
     
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    I agree about the Millermatic 35! The first thing I'd do after looking for obvious bad componets(burned or split, etc.) is spray down the board with contact cleaner. My MM35 boards are not coated, the traces are open with no covering lacquer on them. The cooling fan will blow grinding dust and welding smoke on the traces and make them slightly conductive between traces. So a good cleaning and try again before doing any thing else is first.
     
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  8. #12

    Expert

    Nov 30, 2010
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    Krylon Clear will do a pretty good fake of a dirt proof coating when you're done.

    The problem with your question is that it kind of asks for "The Idiot's Guide to Welders" and that takes a small book, most of which will not be relevant. The "right" way to do it is to understand what makes it tick. After we run you through a couple of these, you will probably know how they work and will take off under your own power.
     
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  9. Fixerman

    Thread Starter New Member

    Apr 23, 2013
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    OK. Thanks guys for the comments. Yea, guess I was asking for "The Idiots Guide To Welders" LOL. It didn't occur to me that it might be impractical to try to do it that way. I guess i had better get one of the machines over to my place, and then start over with your help. I'll clean circuit board as suggested by shortbus and see what happens.

    I will post again once I get a chance to pick up a unit and do some symptom checking and a little basic troubleshooting (power problems, circuit breakers, etc.).

    Thanks again for setting me straight on the proper path to follow. I will be back with a little more reasonable request for help.
     
  10. Rbeckett

    Member

    Sep 3, 2010
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    Contact user 7A749 on the welding web site and he will probably know exactly what is wrong and where to look.
    Bob
     
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