mike 109444
Member
- Messages
- 4,747
Hurray .....think it was getting to the stage of trying a different colour for the case next 
- Thread starter A1EK
- Start date
I know mate, just hate to let things like this beat me! At least I learned loads on the function of the unit!Hurray .....think it was getting to the stage of trying a different colour for the case next
One thing most people miss when troubleshooting with voltage applied is sometimes you can get a voltage reading that looks good, but when a load is applied, the voltage drops out, You can sometimes get the proper voltage reading through a bad connection, but it is just a trickle of electrons that drops to 0 volts if you put a load on it, because the Amps/flow is restricted.
It is called a false voltage.
Comparing it to water, say you have a 1 inch water line connected to a gauge, but inside that water line it is blocked off to the size of pencil lead, as long as the faucet is off the pressure will go through the pencil size opening and the gauge will show you have good line pressure, but when you open the faucet next to the gauge, the water barely trickles and the pressure drops to zero..
A bad component such as a diode, resistor, transformer, or any connection point can be compared to the pencil size passage in the water line.
You need to start at the input to the transformer having a volt meter with clips so you can hook it up hands free, and see at what place down the line in the circuit you lose voltage when you apply the load, in this guys case connecting the welding wire to the ground intermittently. This fault condition can happen with both ac and dc voltages.
I have had it happen through a bad car battery terminal, the starter load ( high Amps) would cause it to arc and the car would start but eventually the connection got so bad the normal operating alternator amps were not high enough to push the charge back in the battery, I thought the battery was bad, bought another one only to find the same problem happened till I changed the battery post.
Working as a Sears technician, once one side of a 230v supply to a dryer had a false voltage. The tech I went to help had changed every part and still the dryer would not turn on.
The voltage at the plug was good 230V but trying to turn it on, one side of the 230v was false dropped to zero, I pulled the plug out enough to get my meter on the plug terminals and had him try and turn the dryer on, the 230V dropped to zero when he hit the start button, checking the breaker at the homes breaker box, it was burnt on one side.
Murphy's law is like this, a connection sometimes will get lose and will build resistance, as the resistance builds at the spot, it causes expansion and contraction and corrosion of the metal at the connection slowly making it more loose till it finally overheats and burns out, or just stops the flow to where not enough power flows to do any work.
I suspect this guy was not able to fix the welder because he was fooled by false voltage. Sh it happens
Reading his troubleshooting, the DC at the gun tip dropped to 18.7 volts DC, the 22v rectified dropped 3.3v and this is with only the circuitry in the volt meter being the load across the gun tip and ground. If he would have taken a jumper wire to strike across the gun tip voltage and ground I am sure that 18.3v dc would have dropped to zero. To me it seems he has a bad diode.
These welders are not rocket science, they simply drop line voltage with transformers and rectify it from AC to DC.. Transformers will have several different windings on the secondary side of the transformer to output different voltages controlled by the switches.
The higher the output voltage the higher the amp flow, that you need for welding thicker metals.
Some circuit designs can variably control the input voltage to the transformer to control the output voltages.
If you are not dealing with a false voltage situation from a bad connection somewhere, The troubleshooting should be easy.
This welder has a primary winding with 2 taps off the primary winding, you can see the #1 relates to the #1 setting, the tap #2 to the # 2 switch setting.
The lower 2 wires say Max (which is a tap) and Min. related to those settings on your switches, even though the diagram does not show the wires connected to #2 and Min.
When you apply voltage to less loops in the primary winding like when you hook power to Max and #2, their is less restriction and more current flow which increases the primary coils magnetism thus increasing the voltage output on the secondary side of the transformer..
My 100E is a 110V welder. I am not sure but I would imagine if your welder input is 230V, the first transformer simply drops the 230V down to 110V , basically a step down transformer providing 110v for the wire drive motor, fan and secondary welding transformer. if the fan and wire drive motor work, the primary transformer is probably good. This leaves only the secondary transformer and the diodes to check. The diagram only shows 2 rectifiers, one to each end of the secondary with a tap in the middle of the winding which is the ground or negative clamp. Due to this configuration if one diode goes bad you still get half the voltage which should be enough to arc but maybe not enough to weld or penetrate..
The simple troubleshooting would be hook a voltmeter set on AC volts across the 2 wires going from the transformer to the diodes, then short across the gun to and ground as if welding, and see if the voltage disappears, if it does the transformer is bad. If not go to the diodes. With your meter on AC volts and with gun tip wire shorted to ground clamp again, put your leads across each diode, if you read an AC voltage across either diode it is bad.
If you can short the welding wire to the ground with little or no arc to melt the wire, it is most likely all the diodes are bad.
