As an old appliance tech this was a fun one to debug. I must say I am an electrical engineer (30 years) and can tell you that I would never specify caps that only have a 6.3V rating if the operating voltage is in the 3-5V range. Way too close between nominal voltages and the max rating. Your asking for troubles in a high heat environment like this. I too had to replace my display caps. In my case on the POD301 type unit the caps were two 330uF and only rated at 6.3V. See pics as they were slightly bulging. Once replaced the POWER ON LED was brighter and more important the oven is behaving much better. There were some higher voltage caps as well but they looked fine. I replaced with 330uF caps but 105C and 16V rated versions. This is only usd for decoupling so they are not that critical to be absolutely drop in replacements. Mine were standard cans I placed sideways and bent the pins to align to the surface pads of the PCB. Just use a bit of sealant or hot glue to hold them in place. A high temp sealant is preferred as the higher heats may melt the hot glue! I used electrical compatible silicone. Standard silicone has acetic acid and will attack a PCB’s wiring as it cures.
For others… The higher voltage rating caps likely will survive the higher temps and abuse a lot longer than lower voltage rated caps. Check the low voltage versions first and look for bulging or a tar like substance that may be on the board near the caps. The electrolyte in the caps can sometimes leak out and this causes the inner laminates to short out and conduct. If you replaced all your suspect caps and you still don’t have good operation verify the power supply board. On my oven there is a separate supply board with more large decoupling caps. I verified all those caps looked fine on my board first. If your supply board is acting up it may also be supplying the 12V for the lights inside the cabinet. Verify you don’t have any issues with voltages at the lights or delivered to the front control module. Could point to the supply board going bad. Lastly verify the large relay board that controls the main elements. There are several large electrolytic type caps on that board. Potential issues are bulging or mis-shaped cans. Lastly there could still be communications issues between the control board and the relay board. On my system the control board only has a 3 pin connector to the front panel. Power, ground, and a single signal. Serial communication is used to communicate to the relay board. If you have fundamental issues with voltages then it’s possible that the received signal has been corrupted so the relay board will misbehave or not respond at all.
Check to see if your oven has a service guide. I luckily found mine online and used it extensively to help isolate the issues.
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