I thought I'd create a new post about this and share some pics.
Due to an accidental fan unplugging, my PCIe cards got extremely hot and ran for an hour before my 100G connection dropped. The transceiver was extremely hot, way beyond normal, and after it cooled it no longer works. Luckily the cards themselves are unharmed.
I've heard these early CWDM4s can have thermal issues, which I have now experienced. Perhaps they undergo thermal runaway, or the earlier designs don't have much thermal headroom. With only a slow fan aimed across the PCIe cards, the exposed metal of the transceiver gets only slightly warm. So it needs airflow but not a lot.
I took it apart, and there is nothing visibly wrong that I can see, but the features are tiny - And it smells like burning electronics inside. Here are some pics:


I put a question mark there but I'm pretty sure it's toast.

There is some thermal interface material on 2 of the chips, and on the optical/electrical converter. Under the microscope there are some interesting features like bond wires:


The optical interface on the LC connector is also interesting. Bare fibers appear to be epoxied into the ceramic ferrules, then they loop around and are fused to those rectangular prism type things that go into the optical/electrical converter.

Due to an accidental fan unplugging, my PCIe cards got extremely hot and ran for an hour before my 100G connection dropped. The transceiver was extremely hot, way beyond normal, and after it cooled it no longer works. Luckily the cards themselves are unharmed.
I've heard these early CWDM4s can have thermal issues, which I have now experienced. Perhaps they undergo thermal runaway, or the earlier designs don't have much thermal headroom. With only a slow fan aimed across the PCIe cards, the exposed metal of the transceiver gets only slightly warm. So it needs airflow but not a lot.
I took it apart, and there is nothing visibly wrong that I can see, but the features are tiny - And it smells like burning electronics inside. Here are some pics:


I put a question mark there but I'm pretty sure it's toast.

There is some thermal interface material on 2 of the chips, and on the optical/electrical converter. Under the microscope there are some interesting features like bond wires:


The optical interface on the LC connector is also interesting. Bare fibers appear to be epoxied into the ceramic ferrules, then they loop around and are fused to those rectangular prism type things that go into the optical/electrical converter.
