ERSA250 reflow oven - power shutdown

Hello everyone!

I have poroblem with reflow oven Ersa250. It is quite old but so far it was working good. Few weeks ago appeared "SUM CHECK ERROR". Helped restart memory using two jumpers from main board. Oven worked without any problem but now he have big overshoot in second top zone and appeared errors messages. Sometimes when the overshoot was big (more than 20 degrees Celsius) oven automatically turn off.

I changed the signal of the second thermocouple and heater with a third. The overshoot was still in second zone -> it's means that a pcb part responsible for second top zone is broken. To make sure i changed second thermocouple and heater with first. Now there is no overshoot. But I have still problem with automatically shutdown.

It is turning off after 1 or 2 hours heating. Re-enable the oven can be when he is cold. When it is still hot oven turning off after few moments.

Any ideas will be nice to see.

Regards

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