HL 600 timer board I think

Looks like you are familiar with all those Hobart mixers. Hope you can help me too.
So I have a HL600. Got it from a school. Was working prior to remove from the school facility.
A month later plugged it in. Worked for like 20 min and stopped.
Bowl still goes up and down but there is no lights on the display.
And mixer wont start at all. Called Hobart. They sent out a tech. He checked the mixer and said all is good with it just the control panel board is bad. Ok So I got another board. Same thing. Mixer worked like 20 min and stopped. All the same sypthoms. Now since the tech said its the board thought OK. Let's put another board on it. And same thing happened again. Mixer stopped, lights disapeared.
Now we have 3 mixers and 3 bad boards I guess.
But I don't think the board is the problem anymore. What's the chance that working machine when I take out the board and put it on another unit it won't work.
The problem must be something else.
Please let me know if you have any ideas how to get them back working.

Much appreciated.
Regards Stoyan

Sorry so late but the reason you need the kit is because the potentiometer (the knob that selects the time) is no longer part of the timer board.You need the pot,and board.I'm a hobart tech,if any other questions let me know.