2PAC Mafia
Member
Hi,
I have a boiler controller with a failure at this Fuel temp. sensor. The type of sensor is OM04-K130-5 2K. In one of the controller is showing a fix value at LCD and when I heat the sensor no changes on it. At another one is showing 0ºC. I have replaced the OP07C and after that both still failing, the fix value changed but it stays fixed and the other one is showing 500ºC.
At both the R10 was hot because it´s black but on both the value is correct, 237K. In one of them the IC was phisically damaged (burnt).
When I tried to measure at a good unit to compare values with scope at PIC pin 18 I see a not measurable signal, it´s a waveform. I see how value is changing at LCD but no visible changes at input of microcontroller. I opened the R27 line to measure mA just in case it was a 4-20mA input but it showed 0mA even with the value changing at LCD.
I´m not sure how to deal with this because I don´t understand the theory of operation...
I attach a schematic and a picture of the unit.
I have a boiler controller with a failure at this Fuel temp. sensor. The type of sensor is OM04-K130-5 2K. In one of the controller is showing a fix value at LCD and when I heat the sensor no changes on it. At another one is showing 0ºC. I have replaced the OP07C and after that both still failing, the fix value changed but it stays fixed and the other one is showing 500ºC.
At both the R10 was hot because it´s black but on both the value is correct, 237K. In one of them the IC was phisically damaged (burnt).
When I tried to measure at a good unit to compare values with scope at PIC pin 18 I see a not measurable signal, it´s a waveform. I see how value is changing at LCD but no visible changes at input of microcontroller. I opened the R27 line to measure mA just in case it was a 4-20mA input but it showed 0mA even with the value changing at LCD.
I´m not sure how to deal with this because I don´t understand the theory of operation...
I attach a schematic and a picture of the unit.