1974 Brain Box saves the day.

Mike69cuda said
Semiconductor technology has changed dramatically in the last 50 years. Switching speeds are much faster. Most of the heat in a semiconductor is generated during switching. Faster switching means less heat generated, which is one reason packages have gotten a lot smaller for the same power handling capacity.

In my opinion, the Chinese replicas are likely unreliable because of the shoddy manufacturing, rather than a different transistor. On the OEM parts, the transistor was firmly and closely attached to the heat sink. In the Chinese version, it appears that the transistor is placed “close” (whatever that means) to the case with some thermal grease blobbed on. It is not mechanically attached. This method is not good for heat transfer. The power handling capability of the TO220 style (and others) transistor goes way up with a good heat sink correctly configured, which the examples are not.

The sand is an interesting twist. No doubt very cheap. I would suspect it acts as thermal storage rather that thermal dissipation. That means it would act like a heat sink until it warmed up, then it wouldn’t do anything.

So it is sounding like it is still a good idea to go in and do my 2 step drilling hack and mechanically fasten the internal heat sink to the external heat sink my means of a screw fastener.

Thank You

Need to do my 1/2" hole Drill through the empty transistor top (top hat) to gain access, then 1/4" drill hole through the control module box to gain access to the internal heat sink tab with the hole in it, then self tap screw it together.

Should be able to do that being the outer heat sink has pre-aligned drill holes underneath the "Top Hat".

So only 2 drill holes to do the task and not having to open the whole case to get inside.