Sorry to bump an old thread, but i had the exact same issue.
Seems like the bridge rectifier for the air is a common failure mode on these. Did not find this thread when searching for some reason, might have saved me the 250 USD i paid for a new heating element hoping that would solve the issue.
The unit i have is a JBC JT-2A hot air station.
The bridge rectifier in question is a DIOTEC B500C1500B. It has a bit unusual pinout so i have not been able to find a substitute (~+~-) Edit: Vishay VS-2KBB100 seem to be equivalent. Have ordered one as it is easier for me to get hold of than the DIOTEC B500C1500B.
Hopefully this will help somebody else having similar issues
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PS: gaborgabor: The IC you are looking for is a Vishay BRT23M optocoupler. Seems like it is obsolete and out of production, but i am sure that there are some similar triac optocouplers with similar specs and package type available if you spend some time comparing the datasheet with filters on mouser/digikey/farnell/or others.