Lincoln 300 300

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I have an old Lincoln 300 300 that a friend was using he stuck the rod and there was a pop from the machine and a burnt smell I let it cool off and opened it up there was a mouse nest which I cleaned out but no sign of anything burned I plugged it back in and it started right up and welded for a short time then shutdown  it does this every time I try to use it. Does anyone have a clue what I should look for I'm not an electrician by a Longshot thanks and have a great day
Reply:First you need to find the code number on the welder. There are at least 3 versions of this welder. the oldest version has a two and three pin receptacles on the front.the newer ones have a round 5 pin receptacle for the remote control.These have a control pcb and a electronic control to control the reactor.Now to your problem, is the welder shutting down and you have to push the power on button to turn it back on or is just the arc starting then turning off?Basic operation of these welders are the same. It is the control circuits that are different. The weld transformer in this welder has two sections. first part is just a step down transformer. lowers voltage and raises available current. second section is the reactor. The range switch on the front picks off different amounts of the reactor to give you a different range of weld current. these reactor are a current transformer and are in series with the weld output. The reactor has two circuits. Command and weld. 10 amps of DC power will control 300 amps of AC power in the high range. with out this command current the reactor will stay at minimum on each range. AS the command current is increased the output current will increase.The old two plug remote send the full command current through the remote control.the round plug units use the remote control to operate a SCR bridge control and pcb. This only put a control voltage in the remote so it doesn't have to work as hard. If the welder does work ok for a minute or so. you will need to look for a loose connection. Something that will heat up under weld load and move to open up.
Reply:

Originally Posted by ccawgc

First you need to find the code number on the welder. There are at least 3 versions of this welder. the oldest version has a two and three pin receptacles on the front.the newer ones have a round 5 pin receptacle for the remote control.These have a control pcb and a electronic control to control the reactor.Now to your problem, is the welder shutting down and you have to push the power on button to turn it back on or is just the arc starting then turning off?Basic operation of these welders are the same. It is the control circuits that are different. The weld transformer in this welder has two sections. first part is just a step down transformer. lowers voltage and raises available current. second section is the reactor. The range switch on the front picks off different amounts of the reactor to give you a different range of weld current. these reactor are a current transformer and are in series with the weld output. The reactor has two circuits. Command and weld. 10 amps of DC power will control 300 amps of AC power in the high range. with out this command current the reactor will stay at minimum on each range. AS the command current is increased the output current will increase.The old two plug remote send the full command current through the remote control.the round plug units use the remote control to operate a SCR bridge control and pcb. This only put a control voltage in the remote so it doesn't have to work as hard. If the welder does work ok for a minute or so. you will need to look for a loose connection. Something that will heat up under weld load and move to open up.
Reply:A picture of the little round thing would help.ChrisAuction Addict
Reply:

Originally Posted by milomilo

A picture of the little round thing would help.
Reply:That is the fan motor run capacitor. If it is failing the motor will not run up to speed and it  will over heat. It should trip the internal thermostat in the motor and turn the motor off until it cools. Get specs off the cap and order a new one from Grainger or other source of electrical parts. If the fan stops other thermostats in the welder might trip and keep the welder from working for 6 to 10 minutes.