I think the topic has been discussed here before but there seems to be some confusion on the compatibility of locomotives with the Märklin 6600 controller.

I have one of these units in the collection, and I'd like to activate it. I have never used one before but have read plenty of horror stories about it destroying electronic components of some types of locomotives.

What seems to be clear from my readings is that the unit can destroy delta and digital chips. But things seem to get a bit complicated for analog locos, so if anyone could shed some light on my confused brain I would appreciate it.

First of all, what is the issue? Is it the same issue as with older Märklin metal or plastic blue transformers, where the voltage used for reversing is too high or is it something else?

I'd like to put together a compatibility matrix so I know which models to use with the unit.

There a quite a few analogue reverser configurations:
a) the traditional mechanical reserver - That would cover locomotives with model numbers 3000 to 31xx series
b) the traditional mechanical reverser with pre switching electronic - some locomotives of the 33xx series
c) the electronic reverser (relay mounted on PCB board) - some locomotives of the 33xx, all locomotives of the 34xx and 35xx series
d) the digital/delta decoder: 36xx series and above.

For type "a", there are no issues, for type "d" there are issues, but what happens with types "b" and "c"?

If it proves to be unsuitable for your layout I'm looking for one...I'm mostly a) with a couple of b)

Thanks for the clarification guys.