Portable Induction Cooktop Error Code EA, then Eb When Turned On

[Agrippa]

Hi, I have a portable induction cook top (Tramontina, model 81500/108) that stopped working. I found the fuse was blown, so tried bypassing it to see if that was all it was. A mistake, as the bridge rectifier blew. Replaced that, but the fuse blew again, so replaced the fuse and both IGBTs. Now it stays on, but it flashes an error code EA. When I press the "on button", it changes to flashing error code Eb. No other symptoms. Fan doesn't come on. It's hard to find anything on these codes, but I believe it is related to detecting the temperature. So I tested the sensors. The thermal cutoff is at near zero ohms (when disconnected), and the thermistor is at about 110k ohms (when disconnected), both normal I believe. What's more, when I hold the thermistor in my fingers while measuring, the resistance slowly decreases. I believe this is also correct behavior. I don't know what to check next. Any help on these codes and what to do/check, or pointing me in the right direction, would be greatly appreciated. Thank you!

 

[kellys_eye]

No point in guessing what error codes mean - they are, if not listed in the user manual, meant for the manufacturers use only and they'll nearly always cite IPA (intellectual Property Rights) and tell you nothing!

For the most part I wouldn't even bother trying to repair one. They are high power, necessarily, with the attendant risks involved in 'getting it wrong'. In my experience they aren't that expensive either and repairs will take time and money. Time to assess whether it is worth the time and effort......

 

[Agrippa]

Thank you. While I don't need the cook top, as an engineer, I am curious about how it works and would like to try fixing it. I have already repaired the high power circuit failure. What I need now is to understand why it is giving an error code EA (which means the cook top is too hot) when I believe the thermistor is normal. I'm looking for help in how this might happen. If it's the temperature controller, then I'm probably not going to do much more here. But if there is some kind of failure related to the thermistor circuit, then perhaps I can still do more. The error code Eb is some kind of unspecified internal failure. Could be anything. So I'm trying to address the overheated EA code first and see where that gets me. So any help along the lines of how you can get a high temperature indication based on a good thermistor would be very helpful. Thanks!

 

[kellys_eye]

If the thermistor checks out then you need to look at the 'other side' of the comparator circuitry that develops the status signal. It may just be a single resistor or it could be a reference voltage from a zener or stabilized source. There might even be an adjustment to set the switching point ????

Along the same lines you will need to check that the supplies to the comparator circuitry are also in spec.