Electronic gurus, need circuit help!

[jmlcolorado]

Any circuit board builders out there?
I need some help on a ........ Kinda ashamed to say .......... Harbor freight welder.
Anyone who knows these welders knows there is a potentiometer for wire speed then 2 switches to select voltage.
1 switch marked Max-Min and the second marked 1-2 for a total of 4 different voltage settings.
I while back the wire feed motor stopped working n half the settings, then suddenly started working again.
Tonight, it started to stop working again. I can hit the trigger and hear the rely switching but the wire feed doesn't work.
I tested the motor and it's not getting voltage when the trigger is pressed.
This board is really simple compared to some, but I know darn close to nothing when it comes to electrical work unless it has wires
It has a few capasitors, 8 or so resisters, a relay, a fuse (which is good) a pot, transformer, somet white box with a lead on each end and marked 5w, and a few other things I can't identify. (might be able to identify after looking online some ).
Can I test resistors and the pot with a multimeter? I assume I'll need to know what the resistance is supposed to be for each one to learn weather or not one is bad.

On the solder side of the board, all the solder joints look okay. Every one going to the transformer is discolored, but not burnt or melted.

I really cant afford a new welder, like literally do not have any money for one

I can take some detailed photos of the circuit board if that helps any.

 

[sgtpontiac]

Is it the flux core or ???

Just wondering.....[S

 

[sgtpontiac]

The HF web site has all the manuals for them...

this one is for the flux core 90amp welder...
http://manuals.harborfreight.com/manuals/68000-68999/68887.pdf

If it's a different one then they should have it for that one......

 

[sneakysnake]

There is a thermal hi limit that will shut down the machine if its hot and will reset. It on page 26 of the wiring diagram to the right of the SI and diodes(upside down triangles)Either your over working the machine(duty cycle) or you may have a diode going bad, or a bad hi limit not resetting. Ohm the limit switch and see if its open.

 

[jmlcolorado]

Just wondering.....[S

Sorry, it's the 110 amp flux welder setup for gas.

There is a thermal hi limit that will shut down the machine if its hot and will reset. It on page 26 of the wiring diagram to the right of the SI and diodes(upside down triangles)Either your over working the machine(duty cycle) or you may have a diode going bad, or a bad hi limit not resetting. Ohm the limit switch and see if its open.

I thought that too but i fired it up last night, got 2 tack welds done and pulled off cause it was welding horribly! I setup a couple pieces of scrap to dial it in to what I was working with, pulled the trigger and the wire hardly moved.
I Pulled everything apart and didn't see any signs of overheating, so I put it all back together and tried it but nothing happened.
Later in the night, I turned it back on, pulled the trigger, with nothing still, changed the temp settings and the feed started for a second but seemed to be struggling, then died again.
I'm gonna call them today and see how much a new wire feed control board is going to cost me :/

 

[Old Iron]

Here's a Google page for resistor color charts
http://www.google.com/search?q=resi...2gWkxPSbDw&sqi=2&ved=0CDkQsAQ&biw=939&bih=570
Check the wires coming off the motor where they plug into the side of the machine to make sure the spades are not loose.

 

[jmlcolorado]

Here's a Google page for resistor color charts
http://www.google.com/search?q=resi...2gWkxPSbDw&sqi=2&ved=0CDkQsAQ&biw=939&bih=570
Check the wires coming off the motor where they plug into the side of the machine to make sure the spades are not loose.

The wires are soldered to the motor.
I have started testing the entire circuit. So far, the transformer is good, 240 in (120 in 2 pins) and 24 volts out.
Pot tests good. MOSFET tests as good as one can test with a multimeter.
Guess its on to testing each resister.

Does this board control making the wire hot when the trigger is pulled too cause the welding wire has no power when the trigger is pulled.

Called HF today, 6-8 weeks out on a whole new board ;(

Im color blind so ive done my best color coding each resistor, now gota go through each one. Ive got some really good pictures of all the components so far, and a friend is trying to help over the phone.

1 step at a time i guess.

 

[jmlcolorado]

There is a thermal hi limit that will shut down the machine if its hot and will reset. It on page 26 of the wiring diagram to the right of the SI and diodes(upside down triangles)Either your over working the machine(duty cycle) or you may have a diode going bad, or a bad hi limit not resetting. Ohm the limit switch and see if its open.

You had me thinking so I retested this theory.
When the thermocouple is connected, I get a click at t he relay on the board, with it disconnected p, I get nothing and the overheat light is on..
I connected the wires going into the thermocouple and the overheat light went off and the relay started to operate again.
So this is in good shape.
I'm still lead to something on the board.

 

[Old Iron]

The wires are soldered to the motor.
I have started testing the entire circuit. So far, the transformer is good, 240 in (120 in 2 pins) and 24 volts out.
Pot tests good. MOSFET tests as good as one can test with a multimeter.
Guess its on to testing each resister.

Does this board control making the wire hot when the trigger is pulled too cause the welding wire has no power when the trigger is pulled.

Called HF today, 6-8 weeks out on a whole new board ;(

Im color blind so ive done my best color coding each resistor, now gota go through each one. Ive got some really good pictures of all the components so far, and a friend is trying to help over the phone.

1 step at a time i guess.

Is there more than one relay ? (IE. motor relay and wire voltage relay)
There should be a large relay that controls the main part of the machine. Check the contacts, I've had them corrode, burn, and get a bug, spider etc. between them.
Check voltage in and out here also that it works.
I think the motor is DC so check the board diodes with the multimeter for continuity, you will have continuity one direction and not the other, the end the stripe is on or the direction of the arrow is the current flow. You can buy these at Radio Shack

 

[jmlcolorado]

Is there more than one relay ? (ie. motor relay and wire voltage relay)
There should be a large relay that controls the main part of the machine. Check the contacts, I've had them corrode, burn, and get a bug, spider etc. between them.
Check voltage in and out here also that it works.
I think the motor is DC so check the board diodes with the multimeter for continuity, you will have continuity one direction and not the other, the end the stipe is on or the direction of the arrow is the current flow. You can buy these at Radio Shack

As far as I see, there is only 1 relay. It has 4 prongs soldered on the board, then 1 smaller gauge wire for the trigger, and 1 large gauge wire. I believe the large gauge wire runs the large transformer.

I'm gonna spend some time tonight testing the resistors, but every time I've seen a resistor fail, it's obviously burned and charred. None of them look That way now.
Thanks for the advice on testing diodes, I'll test them tonight to. There are about 4 on the board.

 

[GJunktionMike]

Have you checked the switches hi/low and the on/off also. some times the contacts arc and lose contact because of build up from arcing. Will not work for awhile then work then not work again. I have had this happen before so it is worth checking.

 

[jmlcolorado]

Have you checked the switches hi/low and the on/off also. some times the contacts arc and lose contact because of build up from arcing. Will not work for awhile then work then not work again. I have had this happen before so it is worth checking.

I kinda jiggled them around. The power switch seems to be working just fine. Maybe I'll pull each wire off, add some dielectric grease and reinstall.

 

[GJunktionMike]

I kinda jiggled them around. The power switch seems to be working just fine. Maybe I'll pull each wire off, add some dielectric grease and reinstall.

Check the switch with a meter. There should be a diagram molded in the side of the switch that shows power in and out. If you have a bad contactor it would be on the inside of the switch and with out pulling the switch apart checking with a meter is the easyest way to check. flip the switch back and forth while testing. I dont recommend pulling a swicth apart if you have never pulled one apart threre is a spring and sometimes a ball bearing that has to go back in one way along with the swicth plate.

 

[jmlcolorado]

Have you checked the switches hi/low and the on/off also. some times the contacts arc and lose contact because of build up from arcing. Will not work for awhile then work then not work again. I have had this happen before so it is worth checking.

YOU are the WINNER!!!
I checked the connections and found most of them to be loose. 1 in particular on one of hp the temp switches wasn't getting current through it [cl
We have full operation again.
THANKS!!!

 

[GJunktionMike]

Your welcome, Just a lucky Guess

 

[sgtpontiac]

goes back to the old addage....

Always check the basics first....power, ground, connnections....great you got it working....[cl

 

[jmlcolorado]

Always check the basics first....power, ground, connnections....great you got it working....[cl

I thought everything else had power since the board checked power going to it just not power out. Thats why I figured something on the board was done.

Lesson learned, start with the basics