⚠️ SAFETY FIRST: IMPORTANT
Modern PCBs are highly sensitive to static electricity and voltage spikes. When troubleshooting, ensure the oven is unplugged. Be aware that a "blown" PCB is often a symptom of another failing component (like a shorted heating element). Replacing the board without fixing the underlying fault will likely destroy the new board immediately.
In more modern ovens a PCB, Relays and sensors do the job of many of the selector switches, This enables very precise and economic control of the cavity heating saving energy and giving better user experience.
Some of the less expensive parts can be easily tested and replaced on PCBs but the more complex chips are not so easy to test find or replace and sometime its better to replace the PCB or it might be more cost effective to buy a replacement cooker oven depending on age of machine.
Some even give error codes it an attempt to help the engineer fault find but if the PCB is dead then this is not possible if you get error codes you will need manufacturer information to find the codes and solutions.
Common issues
PCB have many components and these can fail over time , it is possible for a failure in an oven component for example a shorted element or sensor to destroy board components so bare this in mind when doing your diagnostics on the machine.
A general rule is that if after testing all other components and eliminating them from diagnosis , and they all test good, then you can assume the PCB is faulty, this is an expensive call so you need to be sure.
Sensor are use to give the PCB accurate temperature measurements of the oven cavity to ensure precise cooking , these are usually NTC type temp sensors
There are other methods to regulate the temperature but the most used today is the NTC sensor, the NTC sensor is a semi conductor and as the temperature in the oven cavity rises the resistance through the sensor decreases which is then used to control the on / off time cycling of the heating element.
NTC sensors monitor the cavity temperature and use this information to calculate if the heating time should be increased or decreased.
To test the sensor you need to set multimeter to ohms and check measurements against manufacturer documents.
Its best to test the ntc at room temperature and measure against known good values but its possible to use hot water to test at a range of temperatures.
Common issues
NTC can fail open circuit as well so will test OL on the multimeter so test for this , it may also trigger an error message depending on age and make - model.
if they test OL or out of specification then replace them
Buy cooker oven spares on Ebay UK here
Buy a good Multimeter on Ebay UK here
In high-end modern ovens, the mechanical selector switch is replaced by a Printed Circuit Board (PCB) and electronic sensors. This "electronic brain" allows for far more precise temperature control and energy efficiency than old-school mechanical systems.
The Role of the PCB
The PCB uses relays and microchips to orchestrate the oven's functions.
Diagnosis: Many boards will display error codes to help identify faults. However, if the board itself is dead, it cannot communicate.
Cost Factor: Replacing a PCB is often expensive. A common rule for engineers is to test every other component first—elements, fans, and sensors—and only replace the board if everything else tests perfect.
The NTC Sensor: The Digital Thermometer
Instead of a gas-filled capillary tube, modern ovens use an NTC (Negative Temperature Coefficient) sensor.
Operation: It’s a semiconductor where resistance decreases as the temperature increases. The PCB monitors this resistance to decide when to cycle the heating elements.
Testing: Using a multimeter set to Ohms, you can measure the sensor's resistance. It’s best to test at room temperature against the manufacturer’s specifications. You can also test its responsiveness by placing it in hot water and watching the resistance drop.
Failure: If the sensor reads "OL" (Open Loop), it has failed internally and will likely trigger an error code or prevent the oven from heating.
No comments:
Post a Comment