Bit like me really
- Thread starter Jonesy-91
- Start date
The red & black wires on top of the rectifier seems on and okay, I’ve attached some more pics for you to guys to dig into
I’ve just tried what @DSR recommended, I set my meter to 200V place one lead on the earth clamp and the other on the tip of the gun. Without pressing the trigger i was getting a reading of 10.4, when I pressed the trigger, the relay clicks and transformer powers up, with a reading of 23.2, I then turned the speed knob up and down multiple times but the motor still stayed idleThis has changed since I was last here. Good that the new SCR is in and bad that it hasn't solved the problem.
I'd hesitate to recommend a new controller simply because of the cost and the fact the the existing controller looks to be undamaged and working - the relay wouldn't click if the transformer had burnt out and you have replaced the SCR with new.
Hutcho and I suggested the wire speed pot - I thought it looked out of position and not flat.
Set your meter to the 200V range, plug the red lead into the right plug marked with a diode symbol, AV and ω and your black lead into the middle connector probably marked common. Connect the other end of the test leads to the earth clamp and the tip of the torch. It may be easier to connect them to the + & - terminals inside the welder...
Power on the welder and press the trigger, the relay should click in and the main transformer power up. You should see a reading on the meter when you do this - I don't know what it is but it I would expect something in the range of 18-40V. If you see 0V, then check your meter is working, also check that you have properly made the connections. We know that you get good current out because you have struck an arc between the cables so you should see a voltage reading, if you don't your meter is at fault or your rectifier is at fault and you are getting AC out instead of DC - try measuring the voltage on the 200V AC range (4 clicks to the right on your meter from the 200VDC position) If you get a voltage reading on AC but not DC your rectifier could be faulty and this could be the source of the problem.
Once you have a known good voltage out, keep the torch button depressed and swing the wire speed knob from min to max and back a few times and see if the motort starts to rotate. At the same time see if you can tell if it feels different to before the damage - i.e. is it tighter than you remember or much looser or just the same, is there a catch at it moves - it could indicate a broken track in the pot etc. If there is no movement of the motor, it all feels smooth and you have a good voltage out then the problem could lie with the controller board BUT it could also lie with an incorrectly placed wire, a missing wire or a broken wire.
At this point, turn the welder off and disconnect the mains power then start having a good look inside the case at all the wires. Check that there are none floating about and disconnected, check that none are snapped or damaged - give them a gentle tug to see if the come away from their terminal etc.
Do you have photos of the inside before you took it to bits - if so have a really good look and compare them with what you have, make sure the wires are on the same way and in the same place as before.
It's a pain to go through, one wire at a time, as you check each wire, mark them with a felt pen as you check each end off etc. to be methodical.
I'd pay particular attention to the wires that come from the rectifier to the PCB - they could well be on the wrong way round. The circuit diagram appears to show there is a diode on the board that will prevent current flowing to the motor if the wires are back to front on the rectifier. The circuit diagram doesn't show great detail of the PCB so this is only an educated guess. If you don't have photos, ask on the forum - somebody somewhere will have a good quality pic of the insides :-)
If this doesn't solve the problem, you are at the point of looking at a new PCB, getting to a shop for servicing or re-purposing the welder - they make good door stops or an interesting focal point for your coffee table
I hope your welding is better than your soldering
In the main the board looks OK, I wanted the pic to see if I could see any broken tracks, dry joints (possibly) or missing/burnt tracks. They all look good to me.
HOWEVER - what doesn't look good is the newly fitted SCR. It's not too clear from the photos and zooming in doesn't help much but it looks as if you have bridged a couple of the pins together with solder. Have a really good look at the pins and make sure they aren't bridged and they are clear all round. It doesn't take much - solder can produce 'whiskers' very fine bridges of solder between points, the gate pin on the SCR typically requires under 1mA to turn the device on so any leakage across the pins can easily affect the operation of the SCR.
I find that one of these (below) and a small jewellers screwdriver for scraping between the pads is useful. Cleaning the joints up really needs something like a porper solder sucker.
In the main the board looks OK, I wanted the pic to see if I could see any broken tracks, dry joints (possibly) or missing/burnt tracks. They all look good to me.
HOWEVER - what doesn't look good is the newly fitted SCR. It's not too clear from the photos and zooming in doesn't help much but it looks as if you have bridged a couple of the pins together with solder. Have a really good look at the pins and make sure they aren't bridged and they are clear all round. It doesn't take much - solder can produce 'whiskers' very fine bridges of solder between points, the gate pin on the SCR typically requires under 1mA to turn the device on so any leakage across the pins can easily affect the operation of the SCR.
I find that one of these (below) and a small jewellers screwdriver for scraping between the pads is useful. Cleaning the joints up really needs something like a porper solder sucker.
The red & black wires on top of the rectifier seems on and okay, I’ve attached some more pics for you to guys to dig into
I’ve just tried what @DSR recommended, I set my meter to 200V place one lead on the earth clamp and the other on the tip of the gun. Without pressing the trigger i was getting a reading of 10.4, when I pressed the trigger, the relay clicks and transformer powers up, with a reading of 23.2, I then turned the speed knob up and down multiple times but the motor still stayed idle
Good signs. The 10.4V is the power from the board to the trigger and to the + of the rectifier. The return from the trigger goes back to pin 1 of the multi connector. 23.2 volts is within the range I would expect and proves that the relay is working, the trigger is working and the main transformer is working.
You have confirmed the wiring from pins 2 and 5 to the rectifier is correct as well. Barring breaks in the wire or broken connectors etc. this would indicate that the power from the main transformer is getting back to the board.
That's all we have left, checking that the voltages from the main transformer are getting back to the board.
Your meter is capable of testing this, the safest way to check this is to totally disconnect the machine from the power and switch your meter to its lowest resistance range - ideally continuity (beeps when probes are shorted) - if no continuity use the 200 ohm setting and check that you get a low reading when the probes are shorted - 0 ohms is ideal but very few meters actually show this - normally you will get something between 0 and 1 ohm. My cheap & cheerful meter reads 0.2 ohms, my expensive, only use on special occasions in case I drop it, meter reads 0 but occasionally blips to 0.1 ohms YMMV.
Turn the PCB upside down so you can see its bottom (ooer missus) and then check the resistance from pin 5 of the multi connector to the + (red) connection on the rectifier. This should read 0-1 ohms. Do the same for pin 2 but to the black connector on the rectifier, again you should get 0-1 ohms. Anything more and you have an open circuit between the pin and the rectifier and power is not getting from the rectifier to the board.
I can't stress enough how important it is that this is done with the machine unplugged - the board has direct connection to mains power so there is a serious risk of electrocution if you have it plugged into the mains. The fact that the board will be upside down exposing the soldered side, will not be securely held in place AND you may well not have enough hands to hold the board securely and two test probes etc. makes the process of testing even more hazardous. In short UNPLUG The machine before you do any testing on the board.
If the wires ring out and connect OK, there is only one conclusion - something else on the board is knackered. Replacing the board is the only real alternative at this point.
Nice & easy this one@DSR which setting is it on my meter for the 200ohm setting? Apologies I’ve never really used a meter before
From the off position, rotate the knob 180 degrees. 200 ohm is the very bottom setting at 6 o'clock.
Make sure your leads are - black to centre socket, red to right socket.
Below are two pics of my 'use when worried it might get fried or dropped' meter (the smudge in the display is due to it being dropped...). They show the settings and also the resistance readings with the leads left open and with the leads touching (right). Note this is set to the 2000 ohm range - it doesn't have anything as low as 200 ohms.
Those numbers don't look right.
Touch the two probes together and make a note of the number you see. (Reading 1)
In the pictures below, touch the red test lead to position 1 on the PCB and the black test lead to position 1 on the rectifier - make sure you have contact with the solder pad on the PCB and also with the metal tab on the rectifier. Note the reading on the meter. (Reading 2)
Do the same but on position 2 marked on the images below (Reading 3).
All three readings should be about the same. 8 ohms is way too high for a straight bit of wire :-)
Touch the two probes together and make a note of the number you see. (Reading 1)
In the pictures below, touch the red test lead to position 1 on the PCB and the black test lead to position 1 on the rectifier - make sure you have contact with the solder pad on the PCB and also with the metal tab on the rectifier. Note the reading on the meter. (Reading 2)
Do the same but on position 2 marked on the images below (Reading 3).
All three readings should be about the same. 8 ohms is way too high for a straight bit of wire :-)
They're not too bad really. You often see fluctuation between readings and the first ste you posted were pretty much what I'd expect. The fluctutations could be due to the battery in your meter being on the way out, you may have got the test probe on a slightly dirtier bit of the contact or you have disturbed a wire a bit and changed its contact resistance. Orders of magnitude like your set of readings are wrong but your second ones are OK.
I think we're coming to the end of line. It's looking like the controller card has had it's day. There's possibly one (nuclear) option left. YMMV and one of the other chaps on the forum may look at it and say have you tried X and that will solve the problem - I don't think it will happen but it's not unknown for me to look too hard and not see the wood for the trees. You will need an external 12V power supply - a good old fashioned battery charger will do - not one of these modern 'intelligent' ones that only work when they have detected the battery is connected.
I wouldn't normally recommend or use the nuclear option - normally the fault would have been isolated and sorted by now but we are struggling with limited diagnostic equipment, experience and access to the fault. Remote fault finding at this level is never the ideal situation. Read the bit below and decide whether you want to have a go. If the board is faulty you have nothing to lose. If the fault lies elsewhere, you could well make a mess of the board with your soldering and subsequent clean up that effectively writes the board off anyway - a lose-lose situation.
The
option
Disconnect the welder from the mains - again H&S - don't do any of the following with the welder connected to the mains. Short out pins 1(K) and 2 (A) on the SCR - deliberately solder bridge them or solder a bit of wire across them. Connect your battery charger's -ve (black) lead to the -ve terminal and the charger's red lead (+ve) to the positive terminal (these are the terminals that you connect the earth clamp and torch to) Turn the battery charger on. The motor should start spinning - if it does, the wiring is good and the board is shot. If it doesn't either the motor is broken or there is a wiring problem or the PCB is knackered. You could try pressing the torch trigger if the motor doesn't spin - there may be a residual path from the torch to the relay and that may click in as well and start the motor - the relay though is normally for switching the mains, it doesn't usually switch the low voltage side.
Bridge the two pins on the SCR as shown below in red. They will be a pain to clean up afterwards but I think the board is stuffed so it won't be a problem really.
I wouldn't normally recommend or use the nuclear option - normally the fault would have been isolated and sorted by now but we are struggling with limited diagnostic equipment, experience and access to the fault. Remote fault finding at this level is never the ideal situation. Read the bit below and decide whether you want to have a go. If the board is faulty you have nothing to lose. If the fault lies elsewhere, you could well make a mess of the board with your soldering and subsequent clean up that effectively writes the board off anyway - a lose-lose situation.
The
optionDisconnect the welder from the mains - again H&S - don't do any of the following with the welder connected to the mains. Short out pins 1(K) and 2 (A) on the SCR - deliberately solder bridge them or solder a bit of wire across them. Connect your battery charger's -ve (black) lead to the -ve terminal and the charger's red lead (+ve) to the positive terminal (these are the terminals that you connect the earth clamp and torch to) Turn the battery charger on. The motor should start spinning - if it does, the wiring is good and the board is shot. If it doesn't either the motor is broken or there is a wiring problem or the PCB is knackered. You could try pressing the torch trigger if the motor doesn't spin - there may be a residual path from the torch to the relay and that may click in as well and start the motor - the relay though is normally for switching the mains, it doesn't usually switch the low voltage side.
Bridge the two pins on the SCR as shown below in red. They will be a pain to clean up afterwards but I think the board is stuffed so it won't be a problem really.
