Airco 300 AC DC Heliwelder IV

Hi, I was wondering if I could get some help with a new to me Airco welder? It was given to me by a friend who picked it up at an auction for free. I recently wired it up and attempted to tig weld a bead. I soon figured out that the current setting potentiometer had no effect on the current applied for each of the low, medium, and high current ranges all were running at max.
So, I did some research and found out that the circuit board is most likely the problem. I then removed the side panel and unbolted the aluminum base with the circuit board. I noticed that one component appeared to be missing the portion above the circuit board.

If any one has a part number and or any information it would be greatly appreciated.

Thanks in advance and have a great day. Nelson

Here is a picture of the board:

it seems like there use to be a simple transistor with B C E leads. These things were used to easily change a defect transistor but that seems to contradict the rest of the print that is sealed in into epoxy or something.

Did you find a component or the remains of a blow up component?

Hola Fordman76, buscando información sobre el AIRCO HELIWELDER IV 300 AC / DC, obtuve este foro, estoy reparando un soldador igual, pero el diagrama eléctrico de la cubierta interna del equipo está dañado, para lo cual necesito el diagrama. Hice el diagrama eléctrico de la PCB, pero me falta la información de varios condensadores, que no lo hacen. Si todavía está interesado, puedo enviarle por correo la información que tengo disponible del equipo. En cuanto al conector al que hace referencia, en mi computadora no lleva ningún componente, es muy probable que sea el conector para el módulo opcional el que permite la pulsación de la soldadura, ya que en el PCB está directamente relacionado con el circuito de control de equipo de soldadura de amperaje.

Hello Fordman76, looking for information about the AIRCO HELIWELDER IV 300 AC / DC, I got this forum, I am repairing an equal welder, but the electrical diagram of the internal cover of the equipment is damaged, for which I need the diagram. I made the electrical diagram to the PCB, but I lack the information of several capacitors, which do not. If you are still interested, I can mail you the information I have available from the team. Regarding the connector referred to by you, in my computer does not carry any component, it is very likely that it is the connector for the optional module that allows the pulsation of the welding, since in the PCB is directly related to the control circuit of amperage welding equipment.
Hello Fordman76, looking for information about the AIRCO HELIWELDER IV 300 AC / DC, I got this forum, I am repairing an equal welder, but the electrical diagram of the internal cover of the equipment is damaged, for which I need the diagram. I made the electrical diagram to the PCB, but I lack the information of several capacitors, which do not. If you are still interested, I can mail you the information I have available from the team. Regarding the connector referred to by you, in my computer does not carry any component, it is very likely that it is the connector for the optional module that allows the pulsation of the welding, since in the PCB is directly related to the control circuit of amperage welding equipment.