82–84 C on Whatsminers is normal. MicroBT's fan curve targets ~83–85 C on the hashboards. Fans won't ramp hard until a board goes past that target or the inlet temp rises. If your hashrate isn't throttling and the chips stay < 90 C, nothing is "wrong". You can test by forcing a fixed fan speed with WhatsMinerTool (Set Fans --> e.g. 90%) to see temps drop.

Very Important: Don't flash random images. Control-board images are hardware-specific (H616 + CB6V10) and the wrong file can brick the controller. If the public download page only shows 20250321, newer builds like 20250701/03 are usually beta/region-gated and only provided by MicroBT support.


You might want to try these steps:

In the miner UI check both fan RPMs are detected and connectors are seated (after a board swap it's easy to mis-seat a fan).
"Restore/Factory" the miner once to clear any mismatched settings after the controller replacement.
Use WhatsMinerTool to try fixed fan for a few minutes; if temps respond, your cooling is fine and the normal curve is just aiming for ~85 C.
If you still want a newer firmware, open a ticket on support.microbt.com with the miner S/N, model (H616), controller HW (CB6V10), and current FW. They'll give you the correct package or push it OTA.

Your temps sound within spec. Only get firmware directly from MicroBT, and only the image matched to H616-CB6V10.