Using 2 regulators (Tait programmer), both in TO-220 packages:
7805 and 7812.  I was planning on securing both of these to the
same heatsink, back to back, but not sure this is such a good
idea now...

The datasheets confirm that the metal tab on each device is
connected to ground, which I will take to mean that it is
internally connected to pin 2.  But the 7812 has its ref pin
offset with 2 diodes (to raise the output to over 13V), so if
I connected both metal tabs together, then the diodes would be
bridged and useless.

So am I assuming correctly here?  I probably don't even need
heatsinks on the 7812 --- I need to calculate that.

Cheers,
-Neil.

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